2 C.B. 3001(39.)- PROGRESS IN NAVAL GUNNERY, 1939 EDITION
CONTENTS
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Page |
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| LIST OF PLATES | |
| INTRODUCTION | |
| PART I. - General Review | |
| PART II. - Anti-Ship Gunnery | |
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42 |
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51 |
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52 |
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80 |
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85 |
| Part III. - Anti-Aircraft Gunnery | 88 |
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88 |
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102 |
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111 |
| Part IV. - Shore Attack and Defence | 116 |
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116 |
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121 |
| Part V. - Material | |
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133 |
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133 |
| APPENDIX I. - Standard Spotting Rules for Main Armaments of Capital Ships and Cruisers | 138 |
| II. - Spotting Rules for Destroyers fitted with Admiralty Fire Control | 143 |
| III. - Spotting Rules for Secondary Armaments of Capital Ships, Main Armaments of Aircraft Carriers, Escort Vessels, Modern Minesweepers, Older Destroyers, Depot and Repair Ships | 147 |
| IV. - Instructions for the Conduct of Close Range Barrage Fire | 150 |
LIST OF PLATES
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| No. | To face Page |
| 1. – Progress of Hitting Results with 4-in. Mark XVI Gun on Twin Mark XIX Mounting during 1938 .. .. .. .. | 90 |
| 2. – Variation in accuracy of Long Range H.A. Fire with Range .. | 95 |
At end of book- |
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3. – Nelson and Rodney, S.S., 16-in., Mark I, Throw-off, H.S.B.P.T., and M.A.C. at Centurion. |
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4 C.B. 3001(39.)- PROGRESS IN NAVAL GUNNERY, 1939 EDITION
INTRODUCTION
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General Information and Instructions for practices were issued in Admiralty Letter M/T.S.D. 56/39/G of 3.3.39.
The new Standardised Spotting Rules were issued in Admiralty Letter M/T.S.D.320/38/G. of 5.1.39 and in C.A.F.O. 353/39.
2. Annual reports from Commanders-in-Chief should reach the Admiralty not later than the 31st December, 1939, those from the Home, Mediterranean and China Fleets in quadruplicate, and from other Commanders-in-Chief and Flag Officers of Squadrons in duplicate.
The advantages of producing Progress in Naval Gunnery early in the year require no emphasis.
3. The re-introduction of a list of “points on which information is required when obtainable from normal practices at the end of each Section has proved of value in focussing attention of specific matters discussed in the book, and in facilitating the compiling and analysing of the reports. This practice has been continued.
4. It has been decided to recommence the half-yearly issue of the confidential book containing selected reports of Gunnery practices. Detailed summaries in Progress in Naval Gunnery of important individual firings have, therefore, been discontinued.
PART I
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GENERAL REVIEW
_____
SUMMARY OF YEAR’S WORK - 1938
Except for the mobilisation of the navy in the September crisis, which inter alia deprived the Home Fleet of the Centurion for the autumn practices, the interference to programmes by the international situation was not so marked in 1938 as in the preceding years.
2. The effect of the inevitable changes of personnel due to expansion is still tending to increase. Methods of easing the situation, including proposals from the fleet, are constantly under consideration, but it is not clear that any improvement can be expected for the present.
3. The conclusion of the investigation of trial low angle spotting rules has been a most satisfactory feature, and it is hoped that the consequent introduction of standardised spotting rules suitable for all types of ship will simplify training at sea and in the schools.
4. This should also permit of greater attention being given to rate-keeping which, with rangefinding, is disclosed by a collective analysis as being the principal cause of poor hitting.
5. The resumption of more regular practices during 1938 made no appreciable difference to the general standard of A.A. gunnery except in the marked progress made in the use of new equipments. The more stringent cinema marking is no doubt partly responsible for the apparent lower standards of recent years, but under the circumstances the indication is that frequent changes of personnel have as much, if not more, influence on results than lack of practice.
6. Some progress has been made with close barrage fire, but at the expense of development in augmenting fire from L.A. guns.
7. It is desired that special attention should be given to obtaining improved accuracy in all forms of A.A. gunnery, particularly in small ships fitted with new equipment. Constant investigation is resulting in the development and production of better equipment, but it is considered that existing equipment is capable of better results than have hitherto been attained.
8. Defence against M.T.Bs. has again suffered for want of suitable targets. The target raft towed by the D/C M.B. did not proved satisfactory, and four D/C motor boats of small size and protected to a limited degree against 2 pdr. practice shot have now been ordered. When delivered t is intended that trials should proceed both in Excellent and in one of the Main Fleets, firing direct at these target boats.
6 C.B. 3001(39.)- PROGRESS IN NAVAL GUNNERY, 1939 EDITION
Principal Object for 1939 Practices
9. Except for the large scale fleet firings, referred to later, this remains the same as for 1938. The development of fire control organisation and procedure on the lines indicated in C.B.3001/38 and amplified in this book, and the attainment of proficiency in the use of the standardised spotting rules is to take precedence over new problems.
Competitive Firings
10. This type of firing has largely been superseded by efficiency tests, and in 1938 was carried out on the China Station only, in addition to efficiency tests by some units. The Commander-in-Chief remarks as follows:-
“A low angle competitive firing was carried out on 23rd August by three 8-in. cruisers, this being the culminating point of individual day practices at Weihaiwei. For the second year in succession this was won by Suffolk.
The question as to the advisability of retaining this practice in the year’s programme is still under consideration. On the China Station, when ships are inevitably separated for a part of the year, such a practice has definite advantages and is preferred to the system of awarding gunnery problems.
Owing to the differences in armament of ships, the high angle competitive firing hitherto carried out, has been put in abeyance, and a squadron firing substituted in lieu. All available ships took part in this practice in 1938 and it was carried out at high speed with ships firing both sides, and culminated in a runner torpedo attack on the firing line, when full avoiding action was taken.”
Efficiency Tests
11. The value of efficiency tests has again been confirmed on stations where circumstances have permitted of their being carried out.
12. A tendency on the part of Officers of Quarters to go into local control as soon as breakdowns begin, instead of first trying intermediate and more efficient methods, has been brought to light. While undue waste of time trying alternatives should be avoided, the much greater efficiency of main control with director firing demands that it should be continued as long as possible, and that opportunities of reverting to it after breakdowns have been dealt with should be looked for.
13. It has been suggested that a prolonged sub-calibre firing in an efficiency test would be valuable for exercising breakdowns. This
type of practice is recommended when difficulties arise in arranging a full calibre efficiency test, and when it is desired to conserve the ammunition allowance for other practices.
Efficiency Badges
14. The award of badges for gunnery efficiency has been adopted generally in the Mediterranean Fleet and for sloops on the Africa Station. Other stations have not adopted the scheme, and the Commanders-in-Chief make no comment, except the Commander-in-Chief, America and West Indies, who considers that the award of efficiency badges would provide an incentive.
Prolonged Firings
15. These practices continue to give value from both the control, ammunition supply and material points of view for the expenditure of ammunition entailed.
16. This year it has been necessary to omit the 8-in. cruisers to avoid complications arising in the relining programme for worn guns. Capital ship main armaments have also been omitted from the programme of prolonged firings in view of the large scale fleet firings which, it is hoped, will be carried out instead.
Large Scale Fleet Firing (C.B.3001/38, page 8).
17. Since the fleet programmes will not permit of concentrating the two main fleets at Malta this year, it has been decided that each fleet should stage their own large scale fleet firing, making the best use of the reduced number of ships for the investigation.
18. An outline of the type of practice proposed including the distribution of fire to be used in the various phases of a fleet action has been received from the Commanders-in-Chief, Home and Mediterranean Fleets. Both fleets intend to carry out the practice in the autumn with a firing line of five capital ships, extended possibly by two cruisers in the Home Fleet. The target line will consist of about five targets, some fast and some slow, and fire will be opened, after approach and deployment, with divisional concentration. Fire will be re-distributed while closing and conclude with a general engagement. Relief spotting aircraft will be employed and W/T jamming introduced.
19. The reduction of the battle line from the original proposal for a combined fleet firing will considerably reduce the strain on communications and the difficulties of the aircraft, but the proposals which are generally concurred in, should provide a more searching test of communications in battle that has hitherto been carried out, as well as a more comprehensive gunnery practice than has been staged for many years.
8 C.B. 3001(39.)- PROGRESS IN NAVAL GUNNERY, 1939 EDITION
20. Further, as some battleships in both fleets will be using G.I.C. concentration while the others use G.M.S. procedure (vide Part II. Paras. 8 to 11), these firings will provide a direct comparison of the effectiveness of the two methods of concentration under similar conditions and it is desired that the Commanders-in-Chief should remark on this question in their reports on the firings.
Duties of Control and Spotting Officers (C.B. 3001/38, pages 9 to 11)
21. Reports show that the principles enunciated have generally proved satisfactory and that opinions are unanimous on the benefits of additional observers and of the separation of the ordering of range spotting corrections from the observation of fall of shot. In some cases, however, the organisation adopted and the procedure followed show a confusion of ideas in the application of these principles, and it is considered that the meaning of some of the paragraphs in C.B. 3001/38 cannot be quite clear, particularly those dealing with the responsibility of the Control Officer.
22. That the Gunnery Officer, as Control Officer, must be responsible for the control of the main armament is not open to question, but from the emphasis which has been laid on his responsibility for the determination and application of spotting corrections, it has in some cases either been inferred that the Gunnery Officer is intended to perform this duty himself, or it has been decided that this is the only method of discharging his responsibility.
If the Gunnery Officer should assume the duty of determining the spotting corrections he will be unable efficiently to perform the more important functions of supervising rate and spotting officers, his principal duty in the control of fire. It is, therefore, undesirable that he should do so.
23. The determination and application of spotting corrections is only one element in the control of gunfire, and the delegation of this duty to the transmitting station cannot be regarded as the shelving of responsibility. Normally the control officer will either hear the corrections being given in his earphones, or he will be able to check the corrections applied by means of the repeat receivers; but he cannot be expected to exercise a degree of supervision necessary to see that every single correction is properly applied without detriment to his other duties. He may be temporarily occupied with the Captain, with the Rate Group or with some other matter connected with the armament, and it is unnecessary and unsound that firing should be delayed while he personally verifies that the drill in one detail is correct.
24. The advantages of “plot spotting” in the T.S. are touched on in paras. 31 to 33 on page 10 of C.B. 3001/38, but from the number for reports describing different procedure with “direct” and
PART 1. – GENERAL REVIEW – DUTIES OF CONTROL AND SPOTTING OFFICERS 9
with “aircraft: spotting it is evident that these need amplification. The essence of this procedure correctly followed is that it remains identical, whether the observation being made use of comes from either the main control, outlying observers, aircraft, or from a combination of any of these; and that in each case and whichever position is controlling the fullest use is made of the results of these observations and of the equipment provided to assist in controlling gunfire.
25. The investigations of trial spotting rules, lasting three years, have resulted in the drawing up of similar rules for aircraft and direct spotting, because it is now generally accepted that aircraft spotting in action will at best be intermittent and it is therefore necessary that it should not require either different rules or different procedure.
26. Consequently it is illogical and contrary to developments to adopt the system of applying spotting corrections in the control position with direct spotting, while, with aircraft spotting, these are applied in the T.S.
27. Other remarks in reports are to the effect that suitable individuals are not available in the control team for T.S. plot spotting; that the control officer wishes to maintain detailed control of range spotting; and that the control officer feels handicapped when wearing headphones by which he can listen to corrections given in the T.S., and to avoid this prefers to give the corrections himself.
28. To take the last point first, a number of other reports require that the control officer’s telephone should be fitted with a switch by which he can connect himself at will to either the rate or the spotting group. These evidently hold the view that the efficient control officer must be in direct telephone communication with all the important units in the control team. This view is fully concurred in.
29. The question of suitable individuals is largely a matter of training, for able seamen and leading seamen as well as officers have become successful spotting plot operators. The T.S. officer should not be used for this duty, but he must be trained to include the spotting plot in his supervisory duties.
30. The remaining point against T.S. plot spotting that “the control officer wishes to maintain detailed control of range spotting: shows reluctance to decentralise for fear a mistake will be made. The result of this attitude, however, is that the much more difficult rate keeping is decentralised completely beyond his control, and suffers accordingly.
31. Experience in practice firings by ships where the procedure is understood and correctly applied, is that plot spotting in the T.S. does not deprive the control officer of control of range, that it
10 C.B. 3001(39).- PROGRESS IN NAVAL GUNNERY, 1939 EDITION
reduces the number of mistakes made in the application of spotting corrections, that it provides a ready means of co-ordinating all information, and that it leads to better rate keeping.
Control Officer’s Plot
32. One or two reports still advocate a plot in the control position for use by the control officer. The objections to this plot are:-
(i) A suitable plot is already provided, or shortly will be, in the transmitting station and it is undesirable to duplicate equipment unnecessarily.
(ii) A plot in the control position cannot reproduce all the information available and is therefore liable to lead to the neglect of information which may make the difference between hitting and missing the enemy.
(iii) If required in the fore control it must also be necessary in the after control, which means still more equipment and personnel for fire control.
(iv) It is most undesirable to increase the congestion already existing in control positions and D.C.Ts.
(v) There is a great deal of evidence from practice firings to show that the plot distracts the control officer’s attention from the target, from rate keeping and the control of fire generally. In action is must be anticipated that he will have no time to devote to a plot except to the detriment of his other duties.
33. The trial of a control officer’s plot arose because the value of the TS. Plot in assisting with more complicated range spotting rules was not fully appreciated. Experience now shows that the control officer’s plot is not only unnecessary but may be a danger, and it is desired that this trial should now cease.
34. While on this subject it is once again emphasized that while the spotting plot in the T.S. is particularly helpful in applying automatic corrections, the plot operator in a well-trained control team will often be in a better position that the control officer to appreciate the hitting gun range on which to base the next group.
36. The Commander-in-Chief, Home Fleet, expresses the following opinion on this subject:-
“In cruisers, it is considered that the application of spotting corrections from a T.S. spotting plot is necessary, and the advantages obtainable from a proper use of this plot are already evident.
Simplicity is considered to be an important requirement in the design of the plot.
In capital ships a form of plot has also been found advantageous, but has been situated in the control position
In modern capital ships it would seem preferable to conform to the arrangement in cruisers.”
PART 1. – GENERAL REVIEW – ADDITIONAL OBSERVERS 11
Additional Observers
36. Various outlying positions have been tried for stationing additional spotter observers, and in peace practices the majority have achieved their object. It is probably, however, that in action only suitably equipped gunnery positions will be satisfactory, if all doubt as to the target to spot on is to be removed. This would rule out the crow’s nest and other positions not fitted with bearing indicators.
37. It is, therefore, considered that outlying spotter observers should only be stationed in the after control and one of the turrets.
Communications for Control and Spotting Officers
Control officers
38. The opinion has been expressed by several ships that the control officer’s telephone should be fitted with a switch to enable him to talk on either the spotting or the rate group. This is concurred in, and arrangements are being made for new construction and ships being refitted to be fitted accordingly. Other ships should do this from their own resources demanding gear as necessary from the dockyards.
Spotter Observers
39. Spotting lamps fitted by ship’s staff have generally proved satisfactory and approval has been given for this arrangement to be adopted in all capital ships and cruisers.
40. The suggestion of one ship to fit the lamps in the control officer’s binoculars is not liked in view of the resulting interference and complication. The ideal is considered to be a self evident lamp box containing two “over’ red lamps and to “short” green lamps for each observing position situated near the control officer, and near the T.S. spotting plot. Corresponding pushes are fitted in each observing position and these are used as follows:-
One “short” push pressed .. Some shots seen short.
One “over” push pressed .. Some shots seen over.
Both over or short push pressed Whole salvo seen “over” or “short”.
One short and one over push .. Straddle observed.
pressed
To simplify wiring and to obviate the danger of a stale report being acted on the lamps should only burn while the push is being pressed.
T.S. Control of Inclination
41. Results have been inconclusive and in many of the reports it is not clear that this method has been given a serious trial. No doubt circumstances have been against the investigation, but there appears to be a considerable body of opinion which deprecates the
12 C.B. 3001(39).- PROGRESS IN NAVAL GUNNERY, 1939 EDITION
idea of adjusting enemy settings on information collected in the T.S. without previous reference to the rate officer aloft, whatever the conditions.
42. Although there is much to be said for this point of view, indifferent rate keeping in spite of better equipment points to faulty methods, and it is concluded that the T.S. is one place where there is scope for improvement.
43. It is not intended that the control officer (or the rate officer beside him) should be deprived of his authority in this respect, but it is essential that available information in the T.S. should be quickly and intelligently co-ordinated, and reliable deductions put into effect with the least delay. The control can be kept informed during the process through the rate group telephone, and by the same means can prevent an obvious and serious error.
44. In order to carry out a complete investigation of this method it might be necessary to station the principal rate officer in the T.S. with inclination observers in the control positions.
45. It is desired that special attention should be given to improved methods of rate keeping throughout the year and investigations on the lines of the foregoing paragraphs are to be continued.
Estimating the Inclination of British and Foreign Warships
46. The Commander-in-Chief, China, makes the following interesting observation:-
“It is most noticeable on the China station that it is far more difficult to estimate the inclination of modern foreign warships than of their British contemporaries. Whereas the British ships have upperworks with vertical edges and large areas of fat surface in the fore and aft line or athwartships, the foreigners, who have clearly considered the matter carefully, are seldom seen with anything but a curved surface, and very broken up vertical lines. In additions, such devices as placing the masts out of the centre line have been observed.”
This question is receiving consideration in the design of new ships but in existing ships it is not clear that anything can be done other than the improvisation which were made use of in the war, such as snaking the rigging and breaking the funnel line by the addition of strips of painted canvas.
Inclinating on the Towing Ship
47. Where tried this has been reported on favourably, except in one or two cases when exceptional yawing of the H.S.B.P.T. occurred. Under these conditions inclinating on the target would probably have been no less misleading, and the realistic practice for observers and inclinometers would appear to outweigh any disadvantages.
PART 1. – GENERAL REVIEW – DIRECT SPOTTING 13
Direct Spotting
48. It has been suggested that judging by straddles by the number of short shots in line is a dangerous practice with multi-gun salvos. This is not concurred in.
Though not infallible shorts are often the only guide, as explained in C.B.3026, page 142, and this aid to spotting must be taken into account.
Position of Splashes on a Representative Target
49. The Commander-in-Chief, Mediterranean, reports:-
“The Rear-Admiral Commanding, Third Cruiser Squadron, refers to the necessity of keeping splashes aft on a representative fast moving target in order to ensure hits amidships. It is important that this should be stressed and always aimed at in Centurion firings as there is a natural and correct tendency to keep splashes ahead in target firings in order to facilitate spotting.”
AIRCRAFT SPOTTING
Accuracy of Fall of Shot for Range
50. A collective analysis showing the average error in yards of aircraft fall of shot reports for all day firings is shown below. The mean errors for 1938 show little change compared with 1937, although a larger proportion of firings were witnessed by acting observers and observers’ mates.
Mean Error of Signalled Reports
| Mean Range | KK |
100 |
200 |
300 |
400 |
500 |
600 |
700 |
800 |
900 |
1,000 or over |
10,000 yards |
73 |
49 |
83 |
99 |
119 |
137* |
132* |
151* |
260* |
- |
- |
12,000 yards |
57 |
46 |
76 |
117 |
103 |
126 |
130 |
130 |
180 |
140* |
252* |
14,000 yards |
70 |
56 |
53 |
99 |
119 |
137 |
170 |
183* |
214* |
170* |
728* |
16,000 yards |
56 |
75 |
113 |
128 |
122 |
182 |
177 |
136 |
141 |
196 |
244 |
18,000 yards |
37 |
41 |
59 |
142 |
124 |
113* |
354* |
195* |
216* |
133* |
- |
20,000 yards or over |
71 |
69 |
75 |
74 |
192* |
182* |
350* |
- |
270* |
- |
427* |
All ranges- |
|||||||||||
1938 |
52 |
59 |
76 |
108 |
124 |
153 |
176 |
176 |
180 |
188 |
277 |
1937 |
57 |
52 |
69 |
85 |
117 |
149 |
170 |
186 |
192 |
167 |
206 |
1936 |
68 |
72 |
81 |
101 |
137 |
178 |
190 |
257 |
194 |
229 |
252 |
Number of observations |
|||||||||||
(1938) |
1,106 |
1,016 |
1,115 |
799 |
556 |
310 |
271 |
144 |
160 |
50 |
70 |
14 C.B. 3001(39).- PROGRESS IN NAVAL GUNNERY, 1939 EDITION
Aircraft Inclination Reports
51. The mean error of aircraft reports of target course in all firings was 10.2º, based on 203 observations
Accuracy of Fall of Shot for Line
52. The mean error of aircraft reports of fall of shot for line was 95 yards, based on 151 observations.
Aircraft Spotting by Pilots
53. In the Mediterranean and China Fleets spotting has on occasions been carried out by the pilot in the absence of the observer, and a midshipman or rating trained to transmit enemy course reports. Results are reported to have been encouraging, and it has been recommended that pilots should be trained and prepared to spot.
54. While in a single ship action spotting by the pilot might be feasible in the absence of fighter opposition it would be out of the question in a fleet action. Training is also a difficult for the machine cannot be flown to give both pilot and observer a view, and the latter at present gets insufficient practice.
55. In the circumstances it is not desired to lay down any policy for spotting by pilots nor to fit permanent circuits and keys in aircraft for the purpose.
Aircraft Spotting Communications
56. In action it must be expected that continuous and reliable aircraft spotting will be the exception rather than the rule and the utmost efficiency in communications is, therefore, required to ensure that it will not be ineffective from this cause.
It follows that experienced telegraphists who will be available for all practices should be employed on the aircraft spotting wave and particularly at the set
57. The speed and accuracy of tuning in spotting aircraft, particularly on H/F waves, is still far from satisfactory. Efficiency in tuning is specially important when relief aircraft are taking over and when shifting wave to avoid jamming.
To assist tuning, crystal wave-metres G.L. are now being supplied to all carriers for calibrating the portable wave-metres for use in the aircraft.
PART 1. – GENERAL REVIEW – AIRCRAFT SPOTTING 15
Provision of a Vertical Scale in Target Practices
58. The Commander-in-Chief, China, reports:-
“No satisfactory method of providing a vertical scale for aircraft spotting has yet been evolved on the China Station. High masts, 80 ft. and 60 ft., have been stepped in the B.P.T.s and H.S.B.PT. respectively. These heights represent the average heights of the foretops and funnels of Japanese cruisers, but the problem of providing a suitable mark for the top of the masts has not been solved. A flag is unsuitable because a flag large enough to be clearly seen at 18,000 yards when full extended is, in practice, only fully extended in wind conditions unsuitable for towing targets.
Bamboo topmasts have been constructed. These make a satisfactory mark from the point of view of the observer, but in spite of every effort to cut down weight, they are too heavy and the small beam of the targets makes efficient staying impossible. A case occurred in which mast and top-mast carried away, bringing down part of the lattice and making the target unmanageable, with the result that it went ashore, and this has resulted in extreme reluctance to use the topmasts at all. It is, however, intended to continue trials:-
(i) using a high mast either end of the target, with flags of appropriate size at the masthead and spread on stays joining them;
(ii) using a sail with boom and gaff at the masthead. A device of this kind, which sets itself according to the wind was seen on a Japanese high-speed target.”
59. These methods might be tried on other stations where difficulty is being experienced. Reports as to their success or otherwise will be welcome.
SPOTTING RULES
60. The reports on spotting rules forwarded in accordance with Admiralty Message 2340/23/9/38 were unanimous in recommending that the spotting rules should be standardised as soon as possible, but detailed proposals for achieving this differed considerably.
61. While some suggested that the 1938 trial rules should be retained unaltered and others stated that the introduction of the zig-zag was too complicated and unnecessary, there was a welcome tendency in all reports to regard the zig-zag groups as a useful adjunct rather than the main basis of the rules, and to emphasise, on the other hand, the importance of good rate keeping.
16 C.B. 3001(39).- PROGRESS IN NAVAL GUNNERY, 1939 EDITION
62. The Commander-in-Chief, Home Fleet, states:-
“My general views on this subject are as follows:-
(a) In the interests of training and efficiency it is essential now to standardise the spotting rules for a term of years.
(b) The 1938 rules are in the main satisfactory.
(c) In formulating the final rules the aim should be simplification and standardisation, with a view to reducing the different sets of rules to a minimum. Alterations to the 1938 rules should only be made with these ends in view.”
63. The Rear-Admiral Commanding the 1st Cruiser Squadron in the following paragraphs expresses a view which is held by a great many experienced officers:-
“(i) My views are that it is most essential not only that spotting rules should be standardised as soon as possible but, more important still, that the rules should be made as simple as possible.
(ii) It is hardly an unfair criticism to say that in the last ten or fifteen years, every time that the Gunnery results over a period have not shown improvement, some squadron or other has suggested a new form of spotting rules in the hopes of getting better hitting results.
(iii) It would not appear that the many changes in the spotting rules have had much effect on the hitting results. On the other hand, the frequent changes in the rules have undoubtedly caused uncertainty in the minds of control officers and have certainly tended to distract the latter’s attention from the real problem which has to be solved if good hitting results are to be obtained, i.e.:-
“Keeping the inclination of the enemy correctly.”
(iv) This is the crux of the whole question of hitting the enemy, and no amount of “trending” or any other form of spotting rule will produce good hitting results if the rate keeping is bad.
(v) There is no getting away from the fact that in spite of improvement in material we have made very little if any improvement in inclination results from 1918 to the present day. This points to faulty methods.
(vi) I believe that we would get improvement if we were to simplify the spotting rules and concentrate our main effort on rate keeping.”
The underlying principle he emphasises must form the basis of any method of controlling gunfire, but in recent years it has been in danger of being forgotten in the search for “ideal” spotting rules.
PART 1. – GENERAL REVIEW – SPOTTING RULES 17
64. The result of the last three years investigations, as revealed by practices and reports from sea, may be summed up briefly as follows:-
(i) The value of the zig-zag group for verifying range and rate is established.
(ii) Normal day action rapid groups are better than rapid salvos, which in the past have allowed “the guns to run away with the control”.
(iii) There is little or no advantage in a separate set of rules for aircraft observation which at best will probably be only intermittent. Minor adjustments in direct rules are all that is required to enable advantage to be taken of “reliable” distance reports.
(iv) Complicated refinements such as the reverse ladder have no particular merit.
(v) There is no apparent reason why the same basic rules should not be suitable with minor adjustments for all low angle armaments.
65. These conclusions were confirmed at a meeting between Fleet and Admiralty officers, and the “Standard Spotting Rules” given in Appendix I of this book were drawn up to embody these principles, and to include the majority of the details recommended from sea.
66. These rules only differ from the 1938 trial rules where changes were necessary to achieve the standardisation and simplicity, which it is considered will outweigh any theoretical disadvantages in their details.
Appendices II and III contain the extracts from the Standard rules which are applicable to destroyers, escort vessels, secondary armaments, etc., and omit, for example, all references to aircraft observation.
It is intended that these rules which have also been issued in Admiralty Letter M/T.S.D.320/38/G, dated 5.1.39, and in C.A.F.O. 353/39 should remain in force for a number of years.
THROW-OFF FIRINGS
Reporting Fall of Shot
67. In a simultaneous throw-off firing using simulated aircraft spotting, the observers of the two firing ships were exchanged and carried out the duties of rake-officer and W/T operator. This proved most satisfactory in reducing lag and eliminating errors, and is recommended for trial.
18 C.B. 3001(39).- PROGRESS IN NAVAL GUNNERY, 1939 EDITION
Marking Fall of Shot
68. The use of two rakes (C.B. 3001/38, page 12, para. 48) has been favourably reported on on all occasions of their use, and this method of marking is now recommended for general adoption.
Aircraft Observation
69. In one or two cruiser throw-off firings aircraft have attempted to spot the fall of shot for range.
In the absence of a scale their reports can only be most erratic and the practice afforded to the observer is too unrealistic to be of any value. When aircraft are employed in throw-off firings it is desired that their activities should be limited to estimating range and bearing, and reporting course and speed.
RANGEFINDING. (C.B. 3001/38, page 13.)
Initial Ranges for Opening Fire
70. The general opinion is that circumstances permitting and under good rangetaking conditions, a reliable rangefinder cut should be awaited before opening fire, but this delay need not be prolonged by waiting for the plot to develop. When ranging is difficult, fire will probably have to be opened with an estimated range based on the horizon method.
71. In the reports, intervals of 30 seconds to one minute are referred to as the permissible delay for a rangefinder range. In practice the analysis charts show that the average interval between the first plotted range and the first salvo is between one and two minutes for capital ships and 8-in. cruisers, and about one minute for 6-in. cruisers.
72. It is apparent, therefore, that such delays do not appear unduly long, but no specified interval can be laid down. The Captain must decide according to the circumstances how long fire may be withheld, bearing in mind the improved accuracy to be expected by not hurrying the first salvo.
Tuning to Rangefinders
73. Initial tuning to rangefinders is not always accurate and frequent opportunities of re-tuning both before opening fire and while finding line are not taken advantage of. Again, during the course of a firing, opportunities of applying a previously determined straddle correction to the mean rangefinder range when spotting is difficult have often been lost.
PART 1. – GENERAL REVIEW – RANGEFINDING 19
74. Plot spotting should enable much fuller use to be made of a good rangefinder plot during an action and, as has been suggested by one ship, should permit the range to be re-tuned during the firing of a deflection group without upsetting the control.
Stereoscopic Rangefinder Trials
75. Although the results of the rangefinder trials at Fort Cumberland since the war were conclusively regarded as being in favour of the coincidence rangefinder to the exclusion of the stereoscopic, a scrutiny of the reports shows that under certain conditions of poor visibility the latter may have the advantage.
76. It is also known that some progressive foreign navies still favour the stereoscopic rangefinder, and it is not beyond the bounds of possibility that developments in the construction of these foreign rangefinders have advanced quicker than our own, resulting in an instrument which is superior to those used in the trials.
77. It has, therefore, been decided to purchase three of the latest foreign stereo-rangefinders and arrange a further series of comparative trials at Fort Cumberland.
Apart from putting the stereo principle to another searching test the trial will provide the first opportunity we have ever had of comparing the optical and constructional qualities of up-to-date foreign rangefinders with our own.
Application of Target Travel Corrections
78. Where used, the rule “always apply” the change in range correction has proved satisfactory and has not upset the control by the distortion of spotting corrections. On the other hand, reports criticise the correctness of this rule on theoretical grounds, and mention occasions such as re-assessing the inclination to remove a large error the wrong side of 90º when the application of the change of range correction may confuse the control.
Such confusion has so far not yet occurred, and the occasions on which confusion may arise, particularly with plot spotting in the T.S., are considered sufficiently rare to retain the new rule “always apply”.
79. In ships not fitted with A.F.C. Tables where the range correction can only be computed approximately on a Dreyer calculator, it is doubtful if the lag and complications of drill justify the invariable application of the change in the correction. When the change is large an arbitrary spotting correction will probably serve the purpose as well as the approximation of the calculator. See C.B. 3026, page 56, para. 31; C.B. 3001/1914-36, page 34.
20 C.B. 3001(39).- PROGRESS IN NAVAL GUNNERY, 1939 EDITION
80. Changes in the deflection, however, according to reports, cannot be treated in the same way, since it will be too difficult to prevent their duplicating the line spotting corrections on frequent occasions.
While this view is concurred in, it is desired to emphasize the accuracy with which the modern fire control table is capable of holding the target for line once the correct deflection has been found. Close co-operation between the rate officer and spotting officer on the question of applying the deflection correction when adjusting the settings should result in the fullest use of the deflection mechanism and a reduction of the line spotting corrections required. This applies particularly at fine inclinations when alterations of course are easily seen and the new inclination is easy to judge.
Enemy’s Speed
81. It frequently occurs that an adjustment to enemy’s speed setting is not made when it drops on an alteration of course, and at best a long delay occurs after re-setting the inclination. The speed across plot operator should be informed when the enemy is reported altering course so that he may anticipate a change in speed, and be in a better position to appreciate the significance of variation in his plot. For large alterations an arbitrary adjustment in speed should be made without awaiting confirmation from the speed across plot.
Spreads
82. These remain about the same as last year and the remarks in C.B. 3001/38, page 44, para. 28, again apply.
83. In addition it is thought that there may be a tendency to attempt too high a rate of fire for the standard of drill achieved. The erratic fall and spreads of B and C salvos indicate that the firing of groups is at times being hurried. It is considered important that maximum output should be worked up to progressively while preserving accuracy.
84. It has been suggested that the overall spread, particularly of multi-gun salvos, is not representative of the hitting power of salvos since about 75 per cent. of the shots fall in a zone about two-thirds of the overall spread in length and centred on the M.P.I. This distribution of shots generally follows the normal law of errors, and deductions from the analysis must take into account that the distribution about the M.P.I. is indicative of potential hitting power, while overall spreads give a measure of the standard of drill, particularly pointer following and ramming, at the guns.
85. The present method of assessing the actual rate of hitting is considered satisfactory, and it is not desired further to complicate analyses by introducing a table of the mean difference of all rounds from the M.P.I.
PART 1. – GENERAL REVIEW – RANGEFINDING 21
Warmer Correction
86. C.A.F.O. 2741/38 recently issued on this subject is reproduced below:-
“The ruling given in C.B. 3026, page 64, para 69, and the instructions issued in C.B.3001/34, page 28, para. 18, have been under review, and it is now clear from the evidence available from experimental firings, which is supported by the results of practices, that with certain types of guns the chances of obtaining hits with opening broadsides will be increased by the application of a warmer correction.
2. It has, therefore, been decided that the following corrections are to be used with full and reduced charges:-
Gun Warmer Correction.
8-in., B.L., Mark VIII .. .. + 300 yards.
6-in. B.L., Mark XXIII .. .. + 200 yards.
4.7-in. Q.F., Mark VIII .. .. + 200 yards.
Warmer corrections for other marks and calibres of guns are not to be used.
3. These corrections are considered the most suitable for full charges at normal opening ranges, but they cannot be regarded as ideal for all conditions, since:-
(a) The warmer effect is purely an M.V. effect which will vary with the range and charge in use.
(b) The difference in M.V. between the “warmer” and subsequent rounds may vary between wide limits and does not appear to be systematic.
(c) The effect is generally only present for the first round from a cold gun.
(d) While generally negative, the sign of the warmer effect on M.V. and range may vary in isolated cases.
For simplicity, however, it is necessary to adopt a standard correction for the respective guns affected.
4. From the foregoing it will be seen that opening broadsides from cold guns are unreliable from the control point of view, whether a warmer correction has been applied or not.”
87. Remarks on the suitability of this correction from experience in practices should be included in the annual reports.
Analysis Chart of Range – Scale
88. Where the scale of the analysis chart differs from that of the range plot on the table the former should be used in preparing the analysis, and a note inserted at the top stating the scale of the table plot.
22 C.B. 3001(39).- PROGRESS IN NAVAL GUNNERY, 1939 EDITION
Cant of Trunnion Error. (C.B. 3001/36, page 90.)
89. The limitations of the method of correcting for canted trunnions, described in C.B. 3001/36, page 90, have been disclosed in practice firings during the year, and proposals have been put forward for additional equipment to enable this correction to be applied more accurately and with less lag.
These proposals will be fully met by the cross-levelling gear which will go into production shortly, and in the meantime temporary additions to fire control equipment cannot be contemplated.
90. It is recommended that either the method described in C.B. 3001/36 should continue to be used or, as suggested by one ship, that the layer and trainer should be taught to fire with the top of the vertical cross-wire above the point of aim as far as conditions permit.
When conditions are beyond these artifices fire must be withheld on a large turn.
USE OF LONG RANGE A.A. ARMAMENTS FOR LOW ANGLE FIRE (G.13)
By Day
91. The Commander-in-Chief, Home Fleet’s views on this problem are summarised in the following paragraphs:-
“(a) In any future war the long range A.A. ammunition will need to be preserved, so far as possible, for its primary purpose.
(b) The threat of a torpedo attack at short range by night, is nevertheless, so considerable that the A.A. armament must be used to defeat the attack. Its use in short range night actions should therefore be practised.
(c) By day the tactical necessity for using the long range A.A. armament for low angle fire is far less and its use in such circumstances will lead to an ineffective expenditure of valuable ammunition.
(d) In the present circumstances in the home Fleet the training of the long range A.A. armament in low angle fire by day can only be undertaken to the detriment of training in more important functions. The development of the use of this armament, for this purpose, should therefore be discontinued in the Home Fleet and low angle day practices should no longer be carried out.”
92. The Commander-in-Chief, Mediterranean, is in full agreement with these views, but the Commanders-in-Chief on other stations, where changes in personnel and conflicting commitments interfere less with training, have not expressed opinions against the development of L.A. fire by day from the long range A.A. armament.
PART 1. – GENERAL REVIEW – USE OF LONG RANGE A.A. ARMAMENTS FOR LOW ANGLE FIRE 23
93. Another recent authoritative opinion on this problem was to the effect that “it is necessary to be prepared to make use of this armament against L.A. targets.”
94. While training difficulties at the present time are fully appreciated, it is doubtful if these alone should control the policy, for, when expansion is complete, and in war, they should largely disappear. On the other hand, the vital factor is considered to be the quantity of ammunition carried, which is specially emphasized by the Commander-in-Chief, Home Fleet.
95. After weighing up all these considerations it has been decided that the problem of using the long range A.A. armament in anti-ship action by day should not b pursued for the present.
By Night
96. Opinion is unanimous that the long range A.A. armament should be used for low angle fire as opportunities occur in night action is spite of limitations discussed in C.B.3001/38, page 23, paras. 109 to 112, which incidentally make no mention of defence by this armament against night aircraft attacks.
97. The annual gunnery reports from sea take into account all three possible functions of this armament at night, and extracts from those of the Commanders-in-Chief, Mediterranean and China, are reproduced below.
Commander-in-Chief, Mediterranean:-
(i) It is considered very desirable that both the H.A. Control Systems and the Star Shell Control Arrangements should be fully manned at night, in view of the probability of night air attacks. If this is done the change-over from Star Shell to H.A. Control System (and so to using the H.A. armament for L.A. fire) presents little difficulty and can be very rapidly carried out. The Fire Buzzers and Telephones merely have to be switched over in the H.A.C.Ss.
(ii) The best arrangements that can at present be made for using H.A.C.S. for surface fire involve the use of a Dumaresq and Vickers clock. In order to compete with greater efficiency against fast targets, it is thought that certain slight modifications to the tables will proved advantageous. These modifications to the H.A.C.S.III have been proposed by Warspite and will be forwarded.
(iii) Although only two guns are normally required for Star Shell, it is not considered that one H.A. battery should ever be used fro Star Shell and surface fire simultaneously from different guns. The reasons for this are, firstly, because confusion is likely to arise and secondly, because four-gun salvos are considered necessary for fire to be effective.
24 C.B. 3001(39).- PROGRESS IN NAVAL GUNNERY, 1939 EDITION
The organisation recommended is:-
(a) Existing Ships with not more than Four single or Two Twin H.A. Mountings Each Side.- All guns to be able to use either Star Shell, H.A. firing, or surface firing by night, but no two of these methods ever to be used simultaneously.
Ammunition for surface firing to be stowed in separate lockers. If ready-use supply is expended, time taken for replenishment must be accepted.
(b) Future Capital Ships with more tan Two Twin H.A. Mountings, or H.A./L.A. Mountings Each Side.- Reserve two mountings for Star Shell only. All the remainder to be ready to engage surface or A.A. targets. Whether the Star Shell firing from two mountings can be continued while engaging surface targets with the remainder must be a matter for trial. Separation of the Star Shell and H.A. Fire Buzzers would be necessary, which would complicate existing fire control gear.”
Report by Suffolk forwarded by the Commander-in-Chief, China:-
(i) In Suffolk, blast from the main armament should not interfere with the 4-in. armament.
(ii) With the existing system the 4-in. guns can follow either the director or the star shell Evershed, but can be in communication only with the H.A.C.P. or the Star Shell control, i.e. when the telephone switch is put to “star shell” the H.A.C.P. cannot speak direct to the guns, but the star shell officer can.
(iii) The 4-in. Control Officer in the director is in touch with the H.A.C.P. under both conditions. With this system both mountings of the battery must be either in Star Shell Control from the Fore Control or in control from the H.A. director and H.A.C.P. for A.A. or L.A. fire. When in Star Shell Control one mounting could be sued for L.A. fire in local control, but this is not recommended as the primary system.
(iv) It is considered that the 4-in. armament on the disengaged side should be prepared to engage a target and that this could be done be re-arrangement of the telephone system so that each mounting separately can be switched to Star Shell Control. Additional communication would also be required between the 4-in. Control Officer and the Star Shell Control Officer.
(v) The organisation would then be:-
(a) Before the “Alarm” – All 4-in. armament on Star Shell control both sides.
PART 1. – GENERAL REVIEW – NIGHT FIGHTING 25
(b) Main armament committed on one side – The 4-in. control officer on the disengaged side stands by for L.A. fire with one mounting star shell control.
(c) Satisfactory illumination of the main armament target – The 4-in. on that side can be split to allow one mounting to be employed for L.A. fire at the main armament target.
(vi) Since at night the 4-in. armament may be required for either star shell, low angle, or anti-aircraft fire, and for anti-aircraft or low-angle fire by day, it is considered that the ready-use stowage of ammunition per gun should be increased.
It is also suggested that the supply arrangements form the magazine should comprise two hoists for each side, one of which each side at night be reserved for the supply of star shell.”
98. The Commander-in-Chief, Home Fleet, does not suggest any detailed procedure to be followed, but states that the employment of the long range A.A. armament for low-angle purposes at night should be definitely limited to short range action on the “disengaged” side.
99. Until detailed reports of practices by the 1st Battle Squadron and 1st Cruiser Squadron are received there is insufficient information available to formulate a definite policy, and the situation remains substantially as set out in C.B. 3001/38, page 23, paras. 109 to 112. The guiding principle should be to ensure that star shell and A.A. fire will not be interfered with by the requirements for L.A. fire, but the organisation should permit of efficient L.A. fire when the opportunity occurs, particularly when conditions are unsuitable for star shell. It is also clear that it is unsound to divide the fire of one battery of four guns between either star shell, H.A., or surface firing.
100. Modifications to communications and to ready-use stowage of ammunition on a standard basis for all ships will be considered as soon as requirements are clearer. Ships must, therefore, temporarily adjust communications as far as they can from their own resources to suit the organisation adopted.
NIGHT FIGHTING
Alarm Procedure
101. The new procedure of reporting “ON” when on the bearing ordered and “TARGET” when the enemy can actually be seen in the sights has now had a thorough trial and has been favourably reported on by all Commander-in-Chief.
102. A modification suggested is that the director should not report “target” until the guns are “ready,” particularly with a fast training D.C.T. and comparatively slow training armament.
26 C.B. 3001(39).- PROGRESS IN NAVAL GUNNERY, 1939 EDITION
It is considered that this contingency can be dealt with by internal organisation if found necessary, but in well-drilled ships no difficulties should arise, and in any ship the turrets should be on by director by the time the bridge can act on the report “target.”
103. It has been decided that the new procedure is to be adopted and the Appendix to C.B. 3026 will be amended accordingly.
104. Opening fire with training by Evershed and laying on the horizon has been found difficult to investigate in peace practices for safety reasons, particularly in ships without D.C.Ts. All recent opinions expressed on the subject are in agreement with C.B. 3026, page 132, para. 81. Under the circumstances, therefore, it is considered that “firing by Evershed” should be regarded as an emergency measure for use only in a last resort in action.
Estimating the Range at Night
105. More attention has been given to practising the estimation of range in all night exercises with, it is reported, beneficial results, but there is still scope for greater accuracy in the opening range in night firings.
In night exercises on bright moonlight nights the general tendency to under-estimate the range on sighting, which may be as much as 7 or 8 miles, was conspicuous.
106. The drill in the transmitting station described in C.B. 3001/38, page 20, para. 88, has proved satisfactory, and it is proposed to include this in the appropriate section in the Firing Manual.
107. It is considered most important that great attention should continue to be paid to these two aspects of training for opening fire at night.
Night Throw Off Firings
108. The use of a searchlight by the target ship to indicate the target line was tried in one practice to investigate the possibility of spotting full gun salvos by direct observation from the firing ship under these conditions.
It has been assumed that overs would not be seen, that straddles in the beam would appear white and shorts would appear black against the beam, but it was found that no reliance whatever could be placed on these assumptions and that spotting was further confused by ricochets from shorts appearing in the beam.
The use of full gun salvos in this type of practice for the purpose of exercising night spotters is considered a waste of ammunition and is not recommended.
PART 1. – GENERAL REVIEW – NIGHT FIGHTING 27
109. This practice emphasised the necessity of deciding the direction of throw-off to suit the relative position of the S/L and control in order to avid interference with the direct observation of splashes.
Rangefinder Control
110. The Commander-in-Chief, Mediterranean, reports:-
“In general the method of control by rangefinders, if cuts are obtained, supported by the fall of shot observed, is considered to be sound. The T.S. officer should have no hesitation in informing the control officer immediately if the range plot develops, and obtaining his approval to tune to the rangefinders even in fire has already been opened.
Where the rangefinder, director and control positions are separated, as in capital ship secondary armaments without D.C.Ts., the danger of the rangefinder picking up the wrong target, if several are present, is too great to allow full rangefinder control to be accepted.”
111. The Rear-Admiral Commanding, 3rd Cruiser Squadron remarks:-
“There seems no reason to alter the policy at present in force in the Third Cruiser Squadron, viz., that rangefinder control should be the primary method at night when in company, spotting corrections only being applied if a ship’s own fall of shot can be distinguished for certain.”
112. These views are concurred in, and it is desired to stress that no opportunity of tuning to a R/F range before hitting is established should be missed.
Use of Illuminants
Searchlights
113. Ships in company at night should bear in mind the following objection to sweeping ahead which has been mentioned by the Rear-Admiral Commanding, 3rd Cruiser Squadron:-
“The sweep forward by the sighting ship for further targets is very liable to blank the line of sight to the original target to such an extent that laying, spotting and rangetaking are impracticable.”
This might necessitate using the after control, if manned, while the sweep is in progress.
28 C.B. 3001(39).- PROGRESS IN NAVAL GUNNERY, 1939 EDITION
Indirect Illumination
114. Night practices carried out during the year have shown that indirect illumination provided by a well controlled searchlight can be effective at short and medium ranges, but at longer ranges spotting and rangefinding difficulties are likely to be experienced.
115. The procedure which will ensure that the attacking ship opens fire immediately the illuminating ship exposes a searchlight has not yet been evolved, even in the comparatively simple conditions of peace practices. In war it is difficult to envisage any procedure which will not involve communication between the two ships with the consequent danger of disclosing their presence.
116. It seems probably therefore that opportunities for the use of indirect illumination in night action will be limited to an unengaged ship seizing a chance of developing effective fire against an enemy already illuminated and engaged. This would be the situation if the illuminating ship were forced to open fire in self defence on account of delay in the attacking ship.
117. From this it follows that a shadowing ship, which will normally be a cruiser or destroyer of inferior armament to the opponent being shadowed, should only be relied upon for indirect illumination after the action has already been commenced by the attacker.
The distraction to be anticipated by the illuminating ship opening the attack may be considerable, but unless her fire is likely to be effective it is question whether it will justify the risk of her destruction before her consorts fire becomes effective.
118. To sum up, the element of surprise which might e attained by initial indirect illumination appears to be impossible to achieve in action, but practice with indirect illumination will be of value in preparation for the other occasions when it will be practicable. To provide realism, the illuminating ship should also engage the target.
119. The following are some of the experiences in night practices using indirect illumination:-
(i) Only splashes near the target can be spotted with certainty.
(ii) Rangetakers in particular have great difficulty unless the searchlight is accurately controlled.
(iii) Own searchlights and/or star shell must be instantly ready to augment the illumination and must be used without hesitation as required.
PART 1. – GENERAL REVIEW – NIGHT FIGHTING 29
(iv) Flank marking reports from the illuminating ship can be made with accuracy and little delay, and arrangements should be made for using them.
(v) Estimated range is more inaccurate than normally in night practices at ranges at which indirect illumination may be used but no delay for a rangefinder range can be accepted. The Commander-in-Chief, Mediterranean remarks:-
“A cruiser with a short loading interval should not hesitate to open fire at night with an estimated range. This applies also to the secondary armament of capital ships, but for the main armament a reasonable delay for a R/F range or the hitting range of the secondary armament is acceptable.”
This view is concurred in.
(vi) The silhouetting effect of destroyers’ searchlights is insufficient unsupported by other illuminants for opening fire except at short range.
120. Further information on the use of indirect illumination and opinions on the points raised in the foregoing paragraphs should be included in annual reports.
Aircraft Flares
121. Weather conditions interfered on several occasions with the use of aircraft flares in night practices. On those practices which were successful the Commander-in-Chief, Mediterranean, remarks:-
“The 3rd Cruiser Squadron report that in a night full calibre Centurion firing with flare illumination it was apparent that although sufficient illumination was provided for laying and spotting of shorts, ranging was not possible.
The use of aircraft flares outside the range of normal illuminants places the user in a position of great tactical advantage, provided the enemy is not similarly equipped. The difficulty of ranging can be overcome to some extent by ranging on the flares themselves. This has been found to be practicable, and although only approximate ranges of the target can be obtained the results are more accurate than those obtained by estimation.
The First Battle Squadron, reporting on this subject state that illumination was most effective and excellent range plots were obtained. The position relative to the target for dropping the flares has not yet been fully established, but trial has shown that one flare burning from 2,500 down to 1,000 feet over or slightly on the disengaged side of the target will provide sufficient illumination for ranging and direct spotting up to 8,000 yards. The frequency and position of dropping the flares in order to maintain one in this position will depend on the
30 C.B. 3001(39).- PROGRESS IN NAVAL GUNNERY, 1939 EDITION
relative wind. Experience to date indicates that it will generally be impossible for aircraft to spot the fall of shot with flare illumination.
The above reports are conflicting so far as ranging is concerned; it appears, however, that good ranging is possible provided the flares are dropped in the correct position.”
122. The firings by the 3rd Cruiser Squadron indicated that bolder initial range corrections than those provided for by the spotting rules may be required when opening fire with an estimated range at the limit of range up to which flares may be effective. This should be borne in mind, but care should be exercised in the use of large “up” corrections owing to the difficulty in spotting overs at night.
Use of Star Shell to show up Movements of an Enemy burning a Searchlight
123. A special trial carried out on the China Station confirms previous experience that a well directed searchlight will probably conceal the movements of a small ship, but that, if a good star shell illumination is maintained ahead and astern as well as behind the enemy, the chances of observing inclination from one or other of the control positions during momentary faulty training of the searchlight are increased. It was considered probable that enough of a large ship would be shown up by good star shell illumination to enable an alteration of course to be observed, but this requires confirmation.
124. The Commander-in-Chief, China, remarks that the use of a searchlight to conceal movements, unless exposed for short intervals only, is likely to be a most dangerous procedure as it will provide an aiming and a ranging mark which may well prove fatal.
Night Spotting
125. One report refers to confusion being caused by ricochets from a salvo out for line falling in the beam of the searchlight and being spotted as the true fall of shot. It is considered that attention to an accurately worked time of flight hooter should help in overcoming this difficulty.
Aircraft Spotting at Night
126. From such further experience as has been gained it seems probably that aircraft reports at night will be unreliable and may be most misleading.
INTRODUCTION OF NEW GUNNERY RATES
127. Details of the new organisation of gunnery non-substantive rates referred to in C.B. 3001/37, page 11, para. 11, were published in A.F.O. 1678/38. The reasons for the new rates, together with the arrangements for the transfer from the old to the new rates, were circulated to all ships in Admiralty Letter N.2901/38 of 16th June, 1938.
128. Although the official date of the transfer to the new rates was the 15th February, 1939, it must be appreciated that it will be some years before the number of officers and men borne in all ships is adjusted to the revised complements. This is due to the training limitations of the Gunnery Schools.
129. In the meantime, Commanding Officers can assist considerably by employing men as far as possible at duties they will be required to perform in the new rate to which they have been transferred, or for which they have been earmarked.
130. Importance is attached to the remarks in Admiralty Letter N.2901/38 of 16th June, 1938, concerning:-
(a) The notation in the Gunnery History Sheet (S.1245) of the action stations held by ratings.
(b) The avoidance of local draftings for the sole purpose of adjusting the complements of ships to that allowed with the new non-substantive rates.
POINTS ON WHICH INFORMATION IS REQUIRED WHEN OBTAINABLE FROM NORMAL PRACTICES
G.1. The working of the control team organisation (paras. 20 to 31 and C.B.3001/8, pages 9 to 11).
G.2. Any difficulties encountered with the standard spotting rules due tot eh absence of a plot in the control position (para. 33).
G.3. The stationing of additional observers (paras. 36 and 37).
G.4. Communications for control and spotting officers (paras. 38 to 40).
G.5. Centralised control of inclination in the T.S. (paras. 45 to 49).
32 C.B. 3001(39).- PROGRESS IN NAVAL GUNNERY, 1939 EDITION
G.6. Difficulties experienced due to the invariable application of changes in the range travel correction, and whether the line correction can be more frequently applied than is normally done at present (paras. 82 to 84).
G.7. Warmer corrections (paras. 90 and 91).
G.8. The use of long-range A.A. guns for low-angle fire at night (paras. 100 to 104).
G.9. Indirect illumination (paras. 118 to 124).
G.10. The use of aircraft flares for illuminating targets at night (paras. 125 and 126).
G.11. The relative advantages of G.M.S. and G.I.C. concentration in the large scale fleet firing (para.20).
PART II. – SECT. A. – BATTLESHIPS AND BATTLE CRUISERS 33
PART II
_______
ANTI-SHIP GUNNERY
_______
SECTION A. – BATTLESHIPS AND BATTLE CRUISERS
1. The following tables show the results obtained in full calibre practices of which reports have been received by the end of 1938. The figures in brackets indicate the results obtained during 1937.
CONCENTRATION OF FIRE
Master Ship Control (G.M.S.)
| Target and Number of Practices | Mean Range |
Full Gun Salvos per Min |
Output, per cent. |
Spread |
Hits per Gun/Min |
Direct – D.
Aircraft – A |
15-inch Pair Ship |
||||||
145 ft. B.P.T. 1 |
16,000 |
1.44 |
77.3 |
539 |
.144 |
D |
6-inch with 15-inch M.A.C. Pair Ship |
||||||
Centurion 1 |
9,300 |
2.25 |
98 |
384 |
.114 |
D |
Individual Ship Control (G.I.C.) |
||||||
15-inch Pair Ship |
||||||
Throw-off 1 |
24,000 |
1.75 |
100 |
- |
.036 |
A (simulated) |
6-inch with 15-inch M.A.C. Pair Ship |
||||||
Centurion 1 |
10,400 |
2.08 |
96.2 |
252 |
.305 |
D |
34 C.B. 3001(39).- PROGRESS IN NAVAL GUNNERY, 1939 EDITION
SINGLE SHIP PRACTICES
2. Day
| Target and Number of Practices | Mean Range |
Full Gun Salvos per Min |
Output, per cent. |
Spread |
Hits per Gun/Min |
Direct – D.
Aircraft – A |
16-inch |
||||||
145 ft. B.P.T. 3 |
17,300 |
1.85 |
99 |
296 |
.092 |
D |
145 ft. B.P.T. 3 |
18,300
(17,700)
|
1.64
(1.60)
|
82.6
(94.4)
|
418
(276)
|
.124
(.057)
|
A |
H.S.B.P.T. 4 |
16,000 |
1.88 |
95.9 |
328 |
.087 |
D |
H.S.B.P.T. 1 |
19,400
(16,000)
|
1.60
(1.95)
|
87
(93.4)
|
178
(326)
|
.155
(.390)
|
A |
6-inch with 16-inch M.A.C. |
||||||
Centurion 2 |
15,600 |
2.13 |
100. |
197(3) |
-152 |
A |
15-inch |
||||||
145 ft. B.P.T. 3 |
15,000
(14,000)
|
2.01
(2.02)
|
90.6
(91.9)
|
246
(253)
|
.165
(.220)
|
D |
145 ft. B.P.T. 2 |
11,200 |
1.92 |
86.3 |
227 |
.152 |
A |
H.S.B.P.T. 4 |
14,200
(13,400)
|
1.92
(2.07)
|
93.5
(88.6)
|
190
(258)
|
.088
(.110)
|
D |
H.S.B.P.T. 12 |
15.300
(14,400)
|
1.90
(1.90)
|
89.9
(88.5)
|
226
(182)
|
.139
(.126)
|
A |
Throw-off 3 |
15,900
(14,000)
|
1.90
(1.91)
|
87.9 |
- |
.073
(.064)
|
D |
Throw-off 4 |
16,500
(15,700)
|
1.71
(1.86)
|
- |
- |
.035
(.073)
|
A (simulated) |
6-inch with 15-inch M.A.C. |
||||||
Centurion 6 |
10,200 |
2.48 |
100 |
171 |
.078 |
D |
3. Night
| Target and Number of Practices | Mean Range |
Full Gun Salvos per Min |
Output, per cent. |
Spread |
Hits per Gun/Min |
Average interval challenge to 1st salvo (seconds) |
16-inch |
No practices | |||||
| 15-inch | ||||||
145 ft. B.P.T. 3 |
3,000
(3,100)
|
1.07
(2.38)
|
94
(100)
|
412
(195)
|
.636
(.459)
|
33 |
6-inch with 15-inch M.A.C. |
||||||
Centurion 2 |
7,500 |
2.51 |
94 |
272 |
.153 |
37 and 190 |
PART II. – SECT. A. – BATTLESHIPS AND BATTLE CRUISERS 35
RANGEFINDING
4.
Armament. |
Error |
Average Error of 1st Salvo. |
Percentage of 1st Salvos to Straddle |
Mean Range |
Average Time Ranging before Open Fire (seconds). |
|
At Open Fire. |
At Cease Fire. |
|||||
16-inch |
546
(90)
|
470
(275)
|
370
(190)
|
23
(90)
|
17,500
(15,400)
|
82 |
6-inch with 15-inch M.A.C. |
225
(317)
|
100
(107)
|
450
(250)
|
0
(16.7)
|
15,600
(13,200)
|
80 |
15-inch |
334
(380)
|
257
(220)
|
500
(480)
|
21.9
(20)
|
14,700
(14,200)
|
120 |
6-inch with 15-inch M.A.C. |
750
(170)
|
164
(75)
|
162
(150)
|
37.5
(33)
|
10,200
(9,300)
|
100 |
INCLINATING
5.
Percentage of Time Inclination Error was |
Percentage of Alterations of Course observed |
Lag.
Seconds.
|
|||
0 to 10º |
10º to 20º |
20º to 30º |
|||
16-inch Instrument |
47 |
44 |
7 |
68
(94)
|
30
(12.1)
|
*Air |
80 |
12 |
8 |
54 |
26 |
Used |
58 |
24 |
8 |
- |
- |
6-inch with 16-inch M.A.C. Instrument |
76 |
24 |
0 |
80 |
20 |
*Air |
82 |
18 |
0 |
80 |
22 |
Used |
84 |
16 |
0 |
- |
- |
15-inch instrument |
75 |
10 |
12 |
88
(86.5)
|
20
(42)
|
*Air |
30 |
33 |
10 |
70 |
41 |
Used |
69 |
12 |
1 |
- |
- |
6-inch with 15-inch M.A.C. Instrument |
89 |
6 |
5 |
90
(60)
|
23
(11.5)
|
Used |
74 |
16 |
5 |
- |
- |
36 C.B. 3001(39).- PROGRESS IN NAVAL GUNNERY, 1939 EDITION
AIRCRAFT SPOTTING
Accuracy of Air Reports of Fall of Shot for Range
6. A collective analysis showing the average error in yards of fall of shot reports in capital ship firings is shown in the following table:-
KK |
100 |
200 |
300 |
400 |
500 |
600 |
700 |
800 |
900 |
1000 or over. |
|
Centurion |
68 |
62 |
84 |
89 |
143 |
99 |
155 |
193 |
268 |
220 |
618 |
Target |
61 |
63 |
66 |
112 |
142 |
113 |
164 |
165 |
209 |
133 |
190 |
All firings- |
|||||||||||
1938 |
62 |
63 |
70 |
105 |
142 |
110 |
161 |
175 |
220 |
162 |
403 |
1937 |
52 |
56 |
69 |
92 |
108 |
147 |
202 |
261 |
287 |
- |
325 |
1936 |
67 |
81 |
116 |
121 |
177 |
339 |
299 |
319 |
233 |
2112 |
292 |
Number of observations (1938) |
312 |
296 |
355 |
241 |
146 |
69 |
62 |
25 |
21 |
3 |
10 |
In general, there has been an improvement in the accuracy of reports of fall of shot of 500 yards and above. The tendency to “under spot” these reports is now less apparent.
Inclination Reports
7. In 71 observations the mean error of air reports of target course was 9.0º. There was a marked improvement in the number of courses or alterations of course signalled.
GENERAL REMARKS
Concentration of Fire
Concentration in the First Battle Squadron
8. The Commander-in-Chief, Mediterranean, states:-
“I am of the opinion that any form of G.M.S. concentration by Warspite and other ships of the First Battle Squadron equipped with Dreyer Tables and outfitted with 4 c.r.h. shell is unlikely to prove successful.
With the forthcoming re-organisation of the First Battle Squadron I intend the fire shall be distributed as follows:-
(1) Warspite will act as a separate unit for fire distribution purposes.
PART II. – SECT. A. – BATTLESHIPS AND BATTLE CRUISERS 37
(ii) In the event of Warspite, being in company with one other battleship, encountering a situation requiring a pair-ship concentration of fire on one target, G.I.C. concentration will be used.
(iii) The primary method of concentration by the remainder of the squadron will be G.M.S.
(iv) The occasions when Warspite will be forced to take part in a three-ship concentration are likely to be rare. As a three-ship G.I.C. concentration is liable to result in the maximum output not being developed, it is proposed that the two consorts shall act as one unit in a G.M.S. concentration with Warspite acting as another unit in a combined G.I.C. concentration.
Alternatively the onus of avoiding interference will be placed on Warspite, who will adjust her times of firing.
This latter method is thought to be quite feasible and is favoured as it avoids any possibility of divisional salvos from the pair-ship concentration being delayed in firing.
The procedure has not yet been tried out when firing, but it is intended to exercise it, and consideration will be given to employing it initially in the large scale fleet firing.”
9. These proposals are concurred in and it has now been decided to lay down the policy that master ship control is not to be used in concentrations by ships with different armaments (or greatly differing range tables) or different fire control equipment, necessitating special drill for the inter-communication of ranges. The instructions on this question affecting cruisers are given in Section B.
Individual Ship Control (G.I.C.)
10. As the result of a long range throw-off par ship concentration with individual ship control by Nelson and Rodney, this method was confirmed as being more suitable tan master ship control for the 16-in. ships, although this type of firing does not bring out the difficulty of accurate spotting with direct observation on nine 16-in. simultaneous splashes, which was the principal reason for originally adopting the G.I.C. method.
11. The signalling procedure laid down in C.B.3026 and S.P.02159, was criticised in minor details mainly in regard to the use of GKK, etc., and in the suggestion that a new signal is required for reverting to proper sectors. It is not considered that the existing instructions leave much room for doubt, but the following notes will be added in S.P.02159 XB.
Table F
G.I.C. Individual Ship Control or Revert to proper sectors for next double salvo
Table J
(iv) These signals are mainly for use in G.I.C. concentration.
38 C.B. 3001(39).- PROGRESS IN NAVAL GUNNERY, 1939 EDITION
Single Ship Practices. Standard of Efficiency attained
12. A collective analysis of the results obtained in all full calibre practices shows a distinct falling off in rate of hitting with a less marked reduction in output, for which it is fair to say that the control generally is in the main responsible.
13. The most pronounced deterioration is in rangefinding and rate-keeping, but control officers and drill in the T.S. must take their share of the responsibility. This state of affairs is particularly disappointing as observation of fall of shot, both direct and by aircraft, has been good.
14. It is appreciated that frequent changes of personnel are a great handicap to both individual and collective training, but the analysis indicates that, for this reason amongst others, more attention to individual training in particular is required. In this connection the necessity of frequent and thorough ranging and inclinating exercises and control drills, both in the working up period and between practices, is stressed.
The value of an accurate initial range needs no emphasis, but his cannot be obtained unless the rangetakers receive almost daily practice.
15. It is confidently expected that the standardisation of the spotting rules and the adjustment and clearer definition of duties in the control team, permitting of better supervision of rate-keeping, will result in considerable improvement. These, however, will not permit of any relaxation in the time and meticulous care which must be devoted to individual training if the desired results are to be obtained in firings,
Simultaneous Engagement by Main and Secondary Armaments
(C.B. 3001/38, page 33.)
16. The following is an extract from the report of trials carried out by Warspite:-
(a) From experience gained to date it is apparent that these arrangements for inter-communication of fire control data may be of great value, but certain additions are necessary to ensure-
(i) That the earliest possible moment when the settings shown may safely be followed can be indicated; and
(ii) That the settings are not followed except when it is intended that they should be.
Unless these arrangements are made the inter-communication instruments may be extremely misleading.
PART II. – SECT. A. – BATTLESHIPS AND BATTLE CRUISERS 39
(b) A proposal that a lamp, operated from the 15-in. T.S. be fitted to indicate to the clock rooms when the 15-in. table is set, has already been made. Although experience has not been sufficient to make a definite recommendation, it is anticipated that the 6-in gun range receiver in the 15-in. T.S. should also be worked in conjunction with a lamp indicating that the range shown is being offered from the clock rooms as a suggestion.
(c) Further, in night actions when several targets are present, as during destroyer attacks, it has been round difficult to guarantee that both armaments are on the same target. It is for consideration whether target compass bearing should also be inter-communicated to prevent each other’s settings being used when the armaments are not on the same target. The need for this will, however, decrease when all armaments are fitted with director control towers, since target indication will then be much more efficient and it should be possible to guarantee that, when desired, both armaments will pick up the same target.
(d) The 15-in. gun range and gun deflection receivers in the clock rooms are considered superfluous now that true range and enemy course and speed are available.”
17. The Commander-in-Chief, Mediterranean concurs in the proposal to fit lamps to indicate when the settings may be followed and it is proposed to make arrangements accordingly in ships concerned. The 15-in. gun range and deflection receivers in the 6-in. clock rooms will be omitted where the true range and enemy setting receivers are fitted.
40 C.B. 3001(39).- PROGRESS IN NAVAL GUNNERY, 1939 EDITION
SECONDARY ARMAMENTS
18. The following tables show the results obtained in secondary armament practices of which the reports were received by the end of 1938. The figures in brackets indicate the results obtained in 1937.
Day
| Target and Number of Practices | Mean Range |
Full Gun Salvos per Min |
Output. Per cent. |
Spread |
Hits per Gun/Min. |
6-inch XXII |
|||||
145 ft. B.P.T. 7 |
9,900
(15,300)
|
3.44
(3.08)
|
93.4
(91.1)
|
157
(278)
|
.245
(.014)
|
Centurion 4 |
11,200
(11,400)
|
3.41
(3.74)
|
94.7
(93.6)
|
214
(316)
|
.057
(.148)
|
Throw-off 4 |
8,800
(11,300)
|
3.97
(3.12)
|
100
-
|
-
-
|
.152
(.039)
|
6-inch XII |
|||||
145 ft. B.P.T. 10 |
7,250
(8,500)
|
3.28
(3.90)
|
92.3
(92.7)
|
200
(194)
|
.206
(.147)
|
H.S.B.P.T. 11 |
10,450
(9,100)
|
4.45
(4.39)
|
96
(97.11)
|
224
(241)
|
.233
(.129)
|
Centurion 5 |
11,500 |
4.35 |
93.5 |
243 |
.072 |
Throw-off 4 |
7,900
(7,700)
|
4.21
(3.23)
|
98.5
-
|
-
-
|
.14
(.051)
|
5.5-inch. |
|||||
145 ft. B.P.T. 1 |
8,400 |
3.45 |
88 |
300 |
.0 |
H.S.B.P.T. 3 |
10,300
(12,100)
|
4.2
(3.73)
|
93
(88)
|
200
(210)
|
.05
(.129)
|
Throw-off 2 |
8,400 |
4.4 |
95 |
- |
.12 |
Centurion 2 |
9,000 |
4.7 |
94.5 |
250 |
.0 |
4-inch. |
|||||
145 ft. B.P.T. 3 |
8,000 |
5.35 |
98 |
303 |
.245 |
Centurion 1 |
5,900 |
5.3 |
81.3 |
242 |
.0 |
19. Night
| Target and Number of Practices | Mean Range |
Full Gun Salvos per Min |
Output. Per cent. |
Spread |
Hits per Gun/Min. |
Average Interval Challenge to 1st Salvo (seconds). |
6-inch XXII |
||||||
145 ft. B.P.T. 4 |
3000
(3,900)
|
3.30
(3.15)
|
91
(96.4)
|
249
(362)
|
.77
(.33)
|
61 |
6-inch XII |
||||||
145 ft. B.P.T. 4 |
3000
(3,100)
|
1.95
(2.99)
|
90.9
(90.6)
|
400
(200)
|
.703
(.403)
|
24 |
Centurion 1 |
2,500 |
4.6 |
100 |
425 |
.568 |
23 |
5.5-inch. |
||||||
Centurion 1 |
4,200 |
3.59 |
93.7 |
195 |
.87 |
35 |
4-inch. |
||||||
145 ft. B.P.T. 2 |
3,300
(5,700)
|
4.1
(5.43)
|
92
(96.2)
|
-
(205)
|
.15
(.18)
|
37 |
Centurion 1 |
4,200 |
1.7 |
100 |
- |
.85 |
70 |
PART II. – SECT. A. – BATTLESHIPS AND BATTLE CRUISERS 41
20. Rangefinding
Armament. |
Error |
Average Error of 1st Salvo. |
Percentage of 1st Salvos to Straddle. |
Mean Range. |
|
At Open Fire. |
At Cease Fire. |
||||
6-inch XXII |
248
(475)
|
210
(227)
|
400
(523)
|
13.3
(9.1)
|
10,000
(12,400)
|
6-inch XII |
366
(226)
|
214
(370)
|
475
(640)
|
16.7
(9.1)
|
9,250
(8,600)
|
5.5-inch |
560
(208)
|
333
(146)
|
665
(577)
|
0
(0)
|
9,100
(12,100)
|
21. Inclinating
Armament |
Percentage of time Inclination Error was |
Percentage of Alterations of Course Observed |
Lag Seconds. |
||
0 to 10º |
10º to 20º |
20º to 30º |
|||
6-inch XXII |
52 |
10 |
19 |
80* |
14* |
6-inch XII |
42 |
37 |
17 |
83* |
21* |
5.5-inch |
80 |
20 |
0 |
75 |
22 |
Standard of Efficiency in Practice Firings
22. There was a general improvement in the standard attained in 1938 practices compared with the previous year. A better grasp of the art of fire control on the part of control officers and improved control drill were the man contributory factors.
23. There is still plenty of scope for progress, and it is hoped that the new standardised spotting rules and the short courses for control officers recently instituted by A.F.O. 2875/38 will prove beneficial.
POINTS ON WHICH FURTHER INFORMATION IS REQUIRED WHEN OBTAINABE FROM NORMAL PRACTICES
B1. The relative advantages of G.M.S. and G.I.C. concentration (paras. 8 to 11).
B2. Simultaneous engagement by the main and secondary armaments (pars. 16 and 17).
B3. The suitability of the spotting rules for secondary armaments with particular reference to the use of rapid groups instead of rapid salvos.
Note from editors- We are currently missing pages 42 through 121
122 C.B. 3001(39).- PROGRESS IN NAVAL GUNNERY, 1939 EDITION
PART V
_______
MATERIAL
_______
SECTION 1. – AFFECTING MORE THAN ONE CLASS OF SHIP
Guns and Mountings
4-in., H.A., Mark XVI and XVI* Guns in 4-in., H.A., Mark XIX Mountings
1. These equipments have been favourably reported on from practically all quarters and are being fitted in an increasing variety of ships.
2. Ejection troubles, the only persistent defects, have finally been found to be due to the yield point of the material of a certain percentage of the cartridge cases being too low for the high chamber pressures now in use. (Further details will be found in C.A.F.O. 3015/38). The design of the cartridge cases has been altered, but there are considerable stocks of the Mark I design to be used up.
3. The modifications to the semi-automatic gear in the mountings (vide A.F.O. 2274/37 and C.A.F.O. 263/38) have been successful in producing satisfactory extraction and ejection in all but a very small percentage of cases, and the temporary modifications promulgated in A.F.O. 2105/37, which were applied to the mountings enumerated in the right hand column in paragraph (11) of C.A.F.O. 262/38, have proved entirely effective.
4. It has, however, been decided to proceed with the fitting of the new pattern gear as laid down in A.F.O. 2274/37 in order to cut down the excessive stresses which are experienced when an occasional tight cartridge case is encountered.
5. Errors for line have been found to be somewhat greater than with the 4-in. Mark V gun on 4-in. H.A. III and IV mountings. This was to be expected, as the product of training mass, gear ration and radius of gyration of the twin equipment, is approximately four times as great as that of the single equipment.
6. Special attention should be paid to training in pointer following, and any difficulties experienced should be reported.
PART V. – SECT. 1. – MATERIAL, AFFECTING MORE THAN ONE CLASS OF SHIP 123
7. Where mountings are less than 70 feet apart and where structural considerations permit, blast screens between the mountings and special extended shields on the mounting itself, are being fitted to overcome the considerable mutual blast interference. (Ships affected are London, Arethusa, Southampton, Edinburgh and Fiji Classes, Hobart, Perth and Sydney and Cumberland and Suffolk on re-arming during 1939.)
8. Where structural considerations do not permit, a “scroll cam” safety firing switch will be fitted which will break the firing circuit in those areas of elevation and training where other guns or control positions are blasted.
9. Blast warning gear will not be fitted to 4-in., H.A., Mark XIX mountings unless a very simple and compact gear can be evolved.
10. Sighting ports of recent mountings (No. 78 and later) have been arranged to give a maximum of 40º elevation on the line of sight of the graticuled barrage fire telescopes Pattern G.344*, which are to be fitted in lieu of the Aldis Unit magnification telescope, Pattern G.344. The sighting ports of 75 in No. of the earlier mountings require modification, vide C.A.F.O. 2493/38.
11. Palm operated percussion firing gear is being fitted to all new equipments to enable an electrically misfired round to be rapidly cleared by percussion. The gear will also be fitted to existing mountings in due course. The drill precautions which become necessary are given in A.F.O. 1698/38.
12. Reduced charge range tables will become available by the middle of this year and it is hoped to issue reduced charges towards the end of the year, with a view to reducing wear during practices.
13. When using reduced charges, the recoil will be too short to operate the normal S.A. gear. Special gear is, therefore, being manufactured and will be issued to ships at approximately the same time as the reduced charge ammunition.
14. A universal type of close-stowing dismounting gear, made of tubular scaffolding has been designed for the rapid replacement of loose barrels without removing the guns from their mounting. The work is well within the capacity of ship’s staff.
15. Sets of the gear will be issued to bases in the first instance, but during war they would also be issued to ships on isolated service.
Note. – All existing 4-in., Mark XVI guns will be modified to 4-in., Mark XVI* (loose barrelled) on expiry of their present life.
124 C.B. 3001(39).- PROGRESS IN NAVAL GUNNERY, 1939 EDITION
Short Range Weapons
16. With reference to C.B. 3001/38, page 131, para. 114 the trials of the larger calibre (0.661-in) gun to replace the 0.5-in. machine gun have been abandoned as this equipment was found not to meet requirements. Opinion is hardening that no weapon smaller than 2-pdr. is really effective in close range A.A. fire and the design of a single mounting to take the 2-pdr. Mark VIII gun is now in hand. This weapon may supersede the 0.5-in. multiple machine gun in due course. Conversion of existing 2-pdr. Mark II guns to take linked ammunition has been successfully carried out, and it is probably that about 400 of these older weapons will be so modified. Increased reliability should result.
17. The conversion of new equipments of 2-pdr. 8-barrelled pom-poms to automatic fire commenced in January this year, and existing guns and mountings will be converted as opportunity offers. It has been decided to leave all 4-barrelled equipments in controlled fire as the elevating efforts in automatic fire are unacceptable for a hand-worked mounting.
18. High-velocity ammunition should become available in June this year, and the conversion of equipments to fire this ammunition is a simple matter.
19. As the crews of most 2-pdr. M mountings are occasionally exposed to the blast of other armaments, a blast protection box is being developed and will do trials shortly. This box will enable the key numbers of the 2-pdrs' crew to remain closed up when the remainder of the crew has been forced to retire for reasons of blast.
20. Arrangements are being made for the supply of anti-glare goggles to ships for the use of the crews of pom-pom directors, 2-pdr. pom-poms and 0.5-in. machine guns. It has been decided that goggles are not required for look-out and other personnel who use optical instruments that are fitted with coloured filters.
GUN CONSTRUCTION
21. Wire Construction, introduced into the British Service in 1890, has now been abandoned, and the manufacture of gun wire in this country has ceased. The last wire-wound gun produced for naval service was the B.L. 8-in. Mark VIII.
22. Modern systems of gun construction are:-
All steel built up.
Loose barrel.
Loose liner.
Monobloc autofrettage.
Monobloc all steel.
PART V. - SECT. 1. - MATERIAL, AFFECTING MORE THAN ONE CLASS OF SHIP 125
All Steel Built-up Construction
23. This is used for all guns 6-in. and above and for a limited number of guns smaller than 6-in. where the rate of wear is not excessive. Guns of this nature consist of breech ring, collars, jacket, and a number of tubes shrunk together.
Loose Barrel Construction
24. As stated in C.B. 3001/37, page 103, this is now the normal method of construction for guns 5.25-in. and below, which, owing to their high rate of fire and high ballistic efficiency, have relatively short accuracy lives. This system is described in C.B. 3001/36, page 93.
Loose Liner Construction
25. Although loose barrel is considered preferable to loose liner construction, the latter system will continue to be used for future supplies of new Q.F. 4-in. Mark V guns and a thin loose liner design is under trial. Existing Q.F. 4-in. Q.V. Mark V guns of the built-up type, when worn out, will be fitted with thick loose liners instead of a new "A" tube, as has been done in the past.
Monobloc Autofrettage Construction
26. In the naval service this system is at present only used for Q.F. 3.7-in. Mark II howitzers. It has been investigated for other guns, but from the manufacturing point of view is not considered to be as suitable as the loose barrel, since relining can only be done by boring out to take a loose barrel. Monobloc autofrettage designs may, however, be used to a limited extent in the future.
Monobloc All-steel Construction
27. This may be used as an alternative to monobloc autofrettage construction, but involves the use of steel with a very high yield point. No designs with this type of construction have yet been considered for the naval service, but it may be a future development for small calibre guns.
Autofrettage
28. The autofrettage process consists of applying internal hydraulic pressure to a tube so as to strain the inner layers of the material beyond their elastic limit. On release of the hydraulic pressure, this leaves the inner layers in compression and the outer layers in tension. The main advantage of autofrettage is that it enables a satisfactory gun to be built with lower yield steel than would otherwise be necessary. It also has the advantage of providing a complete static mechanical test of the whole length of the tube. This process is applied to loose barrels and loose liners as well as to the monobloc design.
126 C.B. 3001(39).- PROGRESS IN NAVAL GUNNERY, 1939 EDITION
Heavy Guns
29. All modern guns are being designed for mounting in circular cradles and have square breech rings for the attachment of balance weights, above and below the gun. The recoil cylinders and recuperators are connected to these balance weights.
DIRECTOR CONTROL TOWERS AND SIGHTS
T.I.C. Gear
30. Deliveries of T.I.C. gear to destroyers have commenced and all new construction ships will be fitted with the gear in the first instance.
Cross-levelling Gear
31. Experimental sets fitted in Hardy and Amphion have proved satisfactory and production for existing and new construction ships will begin at the end of 1939. The gear will include the arrangements for setting "throw-off" at the director.
Gyro Sights
32. The Type "P" Sight will be fitted in "L" class destroyers and Dido and later cruisers. Arrangements have been made for utilising the separate gyro stabilising unit to relay stabilisation to the rangefinder, inclinometer and control officer's binoculars. In destroyers it will provide angle of sight to the F.K.C.
33. In the "H" and "J" Sights the difficulty of keeping gyros upright by "A" adjustment has led to the fitting of electro-magnetic control of the gyro. "A" adjustment will be automatic and "B" adjustment controlled by hand. This arrangement, which results in the saving of one man, will be fitted in reconstructed capital ships and "K" class destroyers.
34. Relays. - Experiments have been concluded by Vernon on the performance of Mark III relays. These improved relays will be fitted in ships and, with T.I.C. gear, may be expected to fire at mid roll in bad weather. Ships with type "P" sights will be fitted with direct firing.
35. Mutual Interference. - To overcome the effect of "mutual wave interference" between projectiles fired simultaneously from guns mounted close together, a delay will be introduced in the firing circuit of one gun of 8-in. and 6-in. twin and of the centre gun of 6-in. triple mountings. In bad weather, when spreads would be prejudiced by the delay, it will be possible to revert to normal firing.
36. The New Bombardment Level, Mark III, is now in general supply for L.A. and H.A. directors, and was used in the 1938 Cape Wrath bombardment practices.
PART V. - SECT. 1. - MATERIAL, AFFECTING MORE THAN ONE CLASS OF SHIP 127
Director Control Towers
37. New D.C.Ts. have been modified to satisfy the demand for an improved all-round view for control officers, together with more space for personnel. The control officer's pill box has been increased in size and fitted with improved windows and the front of the D.C.T. has been enlarged.
38. Wind tunnel tests have also been carried out in an effort to overcome the ill effects of draught and noise on communications and personnel. It is hoped that new construction ships will be fitted with suitable baffles to the D.C.Ts., provided that these can be satisfactorily adapted to the surrounding bridge structure.
FIRE CONTROL EQUIPMENT
Admiralty Fire Control Clocks for Q.F. Guns
39. The present design of R to E conversion gear in Admiralty fire control clocks permits of partial charge-changing arrangements for only one other charge in addition to full charge. Since the introduction of reduced charges for certain Q.F. guns, 4 in. and above full and reduced, on an equivalent range basis, will be the two charges catered for in future clocks. To avoid additional complication for sub-calibre firing, a further equivalent range scale will have to be used on these clocks to give the required elevation, but it will be necessary to accept inaccurate rate, time of flight, range and line correction.
40. Certain existing clocks calibrated for full charge and sub-calibre, will be required to be used with reduced charge. To avoid mechanical modifications to these clocks it is intended to adopt them for reduced charge by using equivalent ranges, and by speeding up the main drive motor electrically to generate approximately the correct rate and time of flight. The range and line correction will, however, be slightly inaccurate.
41. Sub-calibre corrector mechanisms will not be incorporated in any future elevation receivers.
AMMUNITION, ETC.
Star Shell
42. Trials with 5.25-in. and 4.5-in. star shell have been completed. It has been decided to accept a minimum range for functioning of 5,000 yards for the 5.25 in. The 4.5-in. shell will function satisfactorily at 4,000 yards.
43. Star shell deflection calculator for 4-in. XVI, 4.5-in and 4.25-in. guns will be calibrated for three "ranges of bursts" - 5,000 yards, 7,000 yards and 10,000 yards.
128 C.B. 3001(39).- PROGRESS IN NAVAL GUNNERY, 1939 EDITION
Tracers
44. A design of tracer for base-fuzed shell, which although not entirely certain in its action is considered good enough for adoption, has been evolved. It will be embodied as far as possible in new designs of shell, and the design questions involved in fitting it to existing shell are being investigated.
Look-out Binoculars
45. The trials with four-power binoculars have been concluded. These binoculars have been found less efficient than seven-power, and general provision is not contemplated.
46. Trials of special ten-power binoculars have been carried out as a result of which arrangements are being made for their supply on a scale of four pairs to each capital ship, aircraft carrier and cruiser. It is intended tat these binoculars should be used on the Captain's Evershed and by the A.D.O.
47. Twelve pairs of seven-power binoculars with a circular graticule in each barrel are being purchased for trial. The graticule should assist in keeping the eyes focused when searching for aircraft.
48. It has been suggested that a detachable rubber facepiece, on the lines of that supplied with pattern 1907A binoculars, would be of value for 1900A binoculars. The matter is being investigated.
Cameras
49. It has been decided that, though gunnery record camera produces a picture which enables a full analysis of close-range aircraft runs to be worked out, this analysis is so laborious as to be impracticable at sea. It therefore follows that such an expensive camera is no longer necessary for general use and no more of this type are being ordered. Trials are proceeding to develop:-
(i) A close-range attack camera to assist in analysing mass attacks, and
(ii) An A.A. verifying camera to assist in the training of close-range A.A. personnel.
50. A small dial camera for photographing A.F.C. clocks in destroyers and director receivers generally is being developed, as also is a director aim camera for checking the aim of the director layer. A camera for marking fall of shot for line is also being tried, but so far the results are not encouraging.
Rangefinders
51. Trials with a small hand held range estimator are proceeding. This estimator uses the optical system of seven-power binoculars and, if successful, should be of value in small ships.
PART V. - SECT. 2. - MATERIAL 129
SECTION 2. - AFFECTING PARTICULAR TYPS OF SHIPS.
A. BATTLESHIPS AND BATTLE CRUISERS
Admiralty Fire Control Tables
Mark VII
52. Experience of the first Mark VII table in Warspite has indicated that, although in general the table is satisfactory, certain drives and associated mechanisms require strengthening, principally owing to the addition of the enemy rate plot. These necessary modifications will be made to existing and future tables.
Mark IX
53. This table for 1936 and 1937 battleships (and Mark IX* (16in.) for 1938 battleships) will be laid out with the main units assembled in the form of a horseshoe, and the remainder mounted adjacent to the T.S. bulkheads. These latter units include the enemy rate plot, inclination plot, inclination report receivers, and dummy enemy ship dial mounted alongside each other at the "Inclination Officer's" position.
Marks I to IV*
54. Arrangements are being made for all these tables to be modified so that enemy travel range correction is always "applied", whilst enemy line corrections remain capable of being applied or not.
Dreyer Tables
55. Arrangements are being made for enemy rate projectors to be fitted to all capital ship Dreyer tables. These projectors should facilitate considerably deducing the "side of 90" from the plot.
Admiralty Fire Control Clocks, Mark IV. (For 6-in. Secondary Armament.)
56. Sufficient of these clocks will be available in 1939 for installing when opportunity offers, in Barham and the remaining R class battleships not already fitted.
57. It is hoped in due course to produce matching units for these clocks to convert the present outcoming equal step gun range transmission to counterdrum receiver in director tower, into unequal follow the pointer movement so as to facilitate director sight setting. Deflection transmission direct to the follow the pointer sights will also be arranged.
130 C.B. 3001(39).- PROGRESS IN NAVAL GUNNERY, 1939 EDITION
GUNS AND MOUNTINGS
16-in., Mark I Triple Mounting
58. These mountings continue to prove generally very reliable. Modifications to the operations of the shell bogies in the shell handing room were tried out in Nelson but did not prove entirely successful in the original simple form. Any improvement will probably require extensive alterations and the matter is at present in abeyance.
59. Some difficulty was experienced in Rodney with scoring of breech screws after the replacement of three worn guns. In future all breech screws will be trued up to the breech bush before a new or relined gun is mounted. Cobalt deposit on the breech screw is also being tried. It is hoped that these steps will prove effective.
15-in., Mark I Mounting
60. The original mountings continue to be entirely reliable. Warspite, the first ship to be converted to the 30° mounting and outfitted with new ammunition, carried out a prolonged firing during last summer. The performance of the turrets was very good indeed.
The history and details of the conversion are briefly as follows:-
61. Early in 1934 Messrs. Vickers Armstrongs were asked to consider the amount of work involved in increasing the elevation of 15-in. gun mountings to 30°. In August of that year the position was clear and a preliminary order was accordingly placed with Messrs. Vickers Armstrongs for the work to be carried out in Warspite, the loss of 1° of depression being accepted.
62. It had been decided to move the trunnion centres 7.25 in. to the rear and to raise them 8.75 in., the slides with guns being moved forward 7.25 in. relative to new trunnion centre. The gun thus projected the original amount outside the turret. The balance of the gun and slide were adjusted by means of suitable balance weights attached to the gun. The existing shields remained unaltered except for new splinter protection plates and enlarged gun ports. No alteration to the ship's structure was necessitated.
63. An additional interlock operated by the gun when it reached 20° elevation, which prevented the breech being opened and the gun loading cage being raised was adopted. New trunnion brackets and arms had to be provided.
64. The main existing items affected by the increased elevation were:-
1. Elevating gear. Enlarged cylinders and longer piston rods were required.
2. Gun sights had to be modified.
PART V. - SECT. 2. - MATERIAL AFFECTING BATTLESHIPS AND BATTLE CRUISERS 131
65. In January, 1935, Messrs. Vickers Armstrongs were instructed to convert the 15-in. mountings of Warspite to pneumatic run-out, by replacing the existing run-in and out ram by one of a different type to act as a recuperator ram, and adapting the run-out cylinder as a recuperator. The run-in cylinder was retained merely as a guide for the tail end of the ram. This modification involved the introduction of an intensifier pump for packing the recuperator gland and a redesign of the recoil cylinder keys.
66. Orders were then given for the conversion of the main armament of Renown, Queen Elizabeth and Valiant on the above lines, but with the substitution of overhead rails for the working chamber radial crane and the adoption of rotary main hydraulic pumps. It is expected that the conversion of all these ships will be completed by the spring of 1940.
New Construction Battleships
67. The main armament of the 1938 programme battleships will be 9-16-in. guns. The 16-in. Mark II mounting will follow the design of the new 14-in. as closely as possible except in so far as provision has to be made for triple, instead of quadruple and twin turrets.
68. The secondary armament of 5.25-in. dual purpose guns remains unaltered. Provision will be made for 6-8 barrelled pom-poms, and none of these will be mounted on turret roofs as was necessary for two of the equipments in the King George V and Duke of York classes. This will enable all equipments to be controlled by directors and fought simultaneously with the main armament.
Shell
69. The 15-in. A.P.C. shell supplied to Warspite (and to be supplied to other ships of the class when reconstructed) have been fitted with 6 c.r.h. instead of 4.c.r.h. ballistic caps. New penetrating caps and relieved bases, fitted at the same time, will bring the perforating power nearly up to that of modern shell.
B. CRUISERS
Spotting Plots. (C.B. 3001/38, page 118)
70. Arrangements have now been made for range-spotting plots of the Galatea type to be supplied in due course to all ships fitted and to be fitted with Admiralty fire control tables, Marks V, VI, VI improved and VI*. Future tables will be fitted with a plot of this type during manufacture.
PART V. - SECT. 2. - MATERIAL AFFECTING BATTLESHIPS AND BATTLE CRUISERS 131
65. In January, 1935, Messrs. Vickers Armstrongs were instructed to convert the 15-in. mountings of Warspite to pneumatic run-out, by replacing the existing run-in and out ram by one of a different type to act as a recuperator ram, and adapting the run-out cylinder as a recuperator. The run-in cylinder was retained merely as a guide for the tail end of the ram. This modification involved the introduction of an intensifier pump for packing the recuperator gland and a redesign of the recoil cylinder keys.
66. Orders were then given for the conversion of the main armament of Renown, Queen Elizabeth and Valiant on the above lines, but with the substitution of overhead rails for the working chamber radial crane and the adoption of rotary main hydraulic pumps. It is expected that the conversion of all these ships will be completed by the spring of 1940.
New Construction Battleships
67. The main armament of the 1938 programme battleships will be 9-16-in. guns. The 16-in. Mark II mounting will follow the design of the new 14-in. as closely as possible except in so far as provision has to be made for triple, instead of quadruple and twin turrets.
68. The secondary armament of 5.25-in. dual purpose guns remains unaltered. Provision will be made for 6-8 barrelled pom-poms, and none of these will be mounted on turret roofs as was necessary for two of the equipments in the King George V and Duke of York classes. This will enable all equipments to be controlled by directors and fought simultaneously with the main armament.
Shell
69. The 15-in. A.P.C. shell supplied to Warspite (and to be supplied to other ships of the class when reconstructed) have been fitted with 6 c.r.h. instead of 4.c.r.h. ballistic caps. New penetrating caps and relieved bases, fitted at the same time, will bring the perforating power nearly up to that of modern shell.
B. CRUISERS
Spotting Plots. (C.B. 3001/38, page 118)
70. Arrangements have now been made for range-spotting plots of the Galatea type to be supplied in due course to all ships fitted and to be fitted with Admiralty fire control tables, Marks V, VI, VI improved and VI*. Future tables will be fitted with a plot of this type during manufacture.
Note from editors- We are currently missing pages 132 through 138
APPENDIX I - STANDARD SPOTTING RULES 139
9. With aircraft spotting the finding ladder group or zigzag group is centred on the range deduced from the aircraft reports for range of the previous deflection group.
10. With aircraft spotting it is essential that the report "over" - "short" - "straddle" be passed to the firing ship without delay. When it can be estimated with confidence the distance of the M.P.I. from the target is to accompany the report. When the difficulties of estimation are likely to delay the signal or make the distances unreliable, the observer is to cease to transmit distances and is to make only GG, SS, etc. When circumstances require it, the omission of distances may be ordered by the firing ship.
11. In the absence of aircraft reports, spotting for range cannot commence until salvos fall in line. Once the target has been located, salvos partially in line should be treated as being on that side of the target on which the shots in line have fallen.
RULES FOR LONG AND MEDIUM RANGE
1. The Groups consist of:-
(a) Deflection Group A series of two or three (normally three except for Capital Ships' Main Armament) salvos with the first salvo to the right of, the second salvo to the left of, and the third salvo at the Calculated deflection. The total spread is to be about two thirds of the deflection danger space of the target in units, but the minimum step between salvos is to be 2 units.
(b) Ladder Group A series of two or three (normally three except for Capital Ships' Main Armament) range salvos laddering towards the target with successive steps of 400 yards. For Capital Ships' Main Armament and Cruisers the second and third steps may be 200 yards each for regaining.
(c) Zigzag Group A series of two or three (normally three except for Capital Ships' Main Armament) salvos spread for range, with the first salvo 200 yards below, the second 200 yards above, and the third at the deduced hitting range.
When using double salvo zigzag groups for Capital Ships' Main Armament, the spread should normally be 100 yards below and above the deduced hitting range. For other ships, it should invariably be 200 yards, whether two or three salvos are fired.
Note. - Aircraft Carriers, Old Destroyers (not fitted with A.F.C. Clocks), Escort Vessels and Capital Ships' Secondary Armament do not use zigzag groups.
(d) Rapid Groups Up to four salvos fired as quickly as possible at the deduced hitting range with no spread between them. In Modern Destroyers (fitted with A.F.C. Clocks) the group is to consist of three salvos.
140 C.B. 3001(39).- PROGRESS IN NAVAL GUNNERY, 1939 EDITION
Finding Line
2. Fire a deflection group at the corrected mean rangefinder range or estimated range. Repeat deflection groups until salvos fall in line, reducing the spread if desired and tuning to the best range (aircraft report included) between each group.
Finding Range
3. Deflection Salvos Straddle. - Correct line if necessary and fire a zigzag group (rapid group in Aircraft Carriers, Old Destroyers (not fitted with A.F.C. Clocks), Escort Vessels and for Capital Ships' Secondary Armament).
4. Deflection Salvos fall Short or Over. - Fire a ladder group:-
(i) Commencing with a 400 yd. correction if confident in the range.
(ii) Commencing with a 800 yd. correction if the range is in doubt.
(iii) Centred on the range deduced from the aircraft report if one is available, the steps being:-
(a) Aircraft report up to 1,000 yards from the target - 200 yards either side of the report.
(b) Aircraft report more than 1,000 yards from the target - 400 yards either side of the report.
(c) Aircraft report GGFF or SSFF -
Two steps of 1,000 yards in the same direction.
or Three steps of 1,000 yards, 400 yards, 400 yards in the same directionNote. - If the aircraft report is only 100 yards from the target, a zigzag group instead of a ladder group is to be fired. In Capital Ships the control officer may fire a double without spreading if desired.
Repeat these ladder groups until the target is straddled or crossed.
5. Ladder Salvo Straddles or Crosses. - Fire a zigzag group (rapid group in Aircraft Carriers, Old Destroyers (not fitted with A.F.C. Clocks, Escort Vessels and for capital Ships Secondary Armament) [Transcribers note - bracket in incorrect position in original document] centred on the hitting range, which is:-
(i) The range of the straddling salvo.
(ii) The centre of the 400 yd. or 800 yd. step which forms the bracket enclosing the target.
(iii) Deduced from the aircraft report nearest the target.
If the bracket is more than 800 yards due to salvos falling out for line, fire a ladder of 400 yards steps in the reverse direction, correcting line as necessary.
6. Whole ladder group falls out for line and there are no aircraft reports.- Correct the deflection and fire a ladder group in the reverse direction, starting at the range on the sights.
7. Final ladder salvo falls out for line and there are no aircraft reports.- Correction the deflection if necessary and repeat this salvo as the first step of a further ladder group.
Maintaining Range
8. Zigzag group encloses the target. - Correct the M.P.I., adjust the rate as necessary and fire a rapid group or another zigzag group if the conditions are difficult, if the rate is in doubt or if the control officer considers it desirable.
9. Rapid group holds the target. - Correct the M.P.I. and rate as necessary and fire another rapid group.
Note. - See Principles, para. 4.
APPENDIX I - STANDARD SPOTTING RULES 141
10. With aircraft spotting. - If reliable aircraft reports are available, make use of them to adjust the M.P.I. but there should be little need for repeating zigzag groups. In capital ships the Control Officer may use his judgment whether to fire unspread doubles, doubles spread ± 100 yards, either side of the deduced hitting range or to modify the correction to the "B" salvo on the report of the previous "B" salvo. The uniform ± 100 yards either side is probably the better method of spreading.
Note. - See also Rule 13.
Regaining Range
11. Target not enclosed by a zigzag group. - Fire a ladder group, starting from the range on sights (i.e. the centre of the zigzag group), and correct the rate.
12. Target not held by two or more salvos of a rapid group. - Fire a ladder group and correct the rate.
13. With aircraft spotting. If the aircraft report is less than 1,000 yards and it is decided not to act as in Rule 10, correct the rate and fire a ladder group with the first step equal to the aircraft report and the remaining steps of 200 yards each in the same direction.
Should the aircraft report be more than 1,000 yards, the first step is to be equal to the aircraft report and the remaining steps 400 yards each in the same direction.
In either case, with only two salvos in the ladder group both steps are to be equal to the aircraft report.
14. Continue ladder groups until the target is regained and then proceed as for maintaining the range - Rules 8, 9 and 10.
Position of Zigzag Group Doubtful
15. In general, if salvos in line fall as expected, repeat the group. If salvos in line do not fall as expected, fire a ladder group unless one salvo straddles, when Rule 8 applies. Rules 16, 17 and 18 cover the situations arising.
16. Whole group out for line. - Correct he deflection as necessary and repeat the zigzag group or make use of any reliable information available from rangefinders or aircraft to adjust the M.P.I. of the next zigzag group.
17. Two salvos out for line. -
(i) If the salvo spotted in line falls as expected repeat the zigzag group.
(ii) If the salvo spotted in line does not fall as expected, fire a ladder group.
18. One salvo of three out for line. -
(i) If the other two enclose the target apply Rule 8.
(ii) If both are on the same side of the target, fire a ladder group and correct the rate.
Maintaining Line
19. If difficulty is found in keeping line, deflection groups may be resorted to and then spotting for range on those salvos in line may take the form of a single step 800 yd. bracket, treating each deflection group as a single salvo for range. The bracket may be reduced as necessary but not below 200 yards.
142 C.B. 3001(39).- PROGRESS IN NAVAL GUNNERY, 1939 EDITION
RULES FOR SHORT RANGE (DAY OR NIGHT) AND OFFICER OF QUARTERS CONTROL (TWO OR MORE GUNS)
20. Open fire with rapid salvos (not groups).
Correction deflection as necessary.
Find range with 800-yard steps and regain range with 400-yard steps. Reduce the bracket to 200 yards, but a 200-yard step must only be used in the reverse direction to the previous 400-yard step.
In Officer of Quarters Control, the O.O.Q. must make the necessary allowance for rate by means of spotting corrections of not less than 100 yards, if instruments are not available.
CONCENTRATION
21. Use the above rules but zigzag groups should be unnecessary and may be omitted at the discretion of the control officer.
Note. - The use of zigzag groups may complicate the duties of the telegraphist transmitting ranges to consorts to such an extent as to outweight their possible advantages.
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