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Fired on pistol butts at 20 yards. Rounds fired.   No. of conveyor     Rectangle.                                                                inches.			Ammunition.—I.C.I. '39. Remarks.
3=10	3. -I k 5	2.8x 3.4	For 10 rounds.
5	1	1.6 x 1.8'
:5	5	22 x 0-7
6	3	2.6 x 1.6	Rectangle for 5 shots.        1 shot off.
		3.3x 2.3	Rectangle for 15 shots.
5	3, 4 & 5		From magazine.

NO. 6,016 --6-0r3-- 113`).            SECRET.
1540

103/0/17 110/1/3/1 110/1/14/1

RIFLES.
Boys 0.55 inch.
Parker Hale conveyors for sub-calibre firing.

Previous No. 5,747/

Comdt.       1f. 40, to Sec. O.B. (re No. 5,747).
The trial has been carried out at Hythe and the following is our report :—
As a training device this method has many advantages over the 0.22 inch rifle attachment. It has been found, however, that in practice its accuracy is nothing like that required, and it will be seen that the rectangles as per the following table are very poor.
In order that this device should be of value in training, its accuracy must reach a standard of not less than,—
1-inch group at 15 yards, or 64 inch group at 100 yards.
If the device will not give a performance up to this standard, it would mean asking a firer to place the shots in a circle on the target, which the weapon itself is not capable of doing. This will readily be seen from Pamphlet No. 18 (Supplement), S.A.T., Vol. I, where the dimensions of the targets for 1/5th scale and 1/30th scale shooting are shown.
After firing tests had been carried out, the armourer staff sergeant inspected the A/T rifle and found that the recoil reducer had been struck several times and very slightly damaged.
It will be noted that a few rectangles were fired with the recoil reducer removed. This did not, however, produce any marked difference in accuracy.
It seems a pity that this device could not be made to shoot straight as, undoubtedly, it would be the better solution to sub-calibre firing.
It should be noted that the A/T rifle sights are about 2 inches offset so that, even if this conveyor were really accurate, a re-drawing of, at any rate, 1/30th scale shooting targets would be necessary.
Accuracy tests with the new rifle and the old will be seen to show practically no difference.
It is my opinion that the fit of the conveyor in the rifle chamber is not tight enough, and this seemed to be the same in both new and old rifles. Whether a 4-inch barrel can ever give the required accuracy should surely be a known factor ; the D.S. of E. considers a 1 inch group at 15 yards to be a high standard for such a length of barrel and is doubtful whether it can be attained.
Will you give instruction for the disposal of the conveyors.
Summary of firing trials.

Action.—Forward to D. of A.

1. The maximum length of the conveyor is limited by the size of the magazine, and the Board are very doubtful if the standard of accuracy required (" X " above) can be obtained consistently with an effective bore length of about 4 inches.
2. The size of group obtained when the conveyors were placed in the same position in the chamber for each round shows that it should be possible to improve the accuracy in normal shooting considerably by improving the fit of the conveyor in the chamber and ensuring that the rifling of the conveyor is co-axial with the outside of the conveyor.

[3. In

NO. 6,016 (contd.)
3.5.40

1. In view of the great advantage of this method of sub-calibre shooting over the 0.22 inch rifle attachment, the Board will continue trials to see what degree of accuracy can be obtained by a better fit of the conveyor, and in the meantime suggest that con­sideration be given to the possibility of lowering the standard of accuracy required by altering the size of the target used.

Will D. of A. consider this.

1. Ask C.S.D., in collaboration with Messrs. Parker Hale, to prepare a design of conveyor for the 0.55 inch rifle, which will give the tightest practicable fit in a new rifle. Inform him that., since it is essential that the " bore " should be as nearly as possible co-axial with the outside of the conveyor, it is suggested that in manufacture the bore should be machined first and the outside turned, using the bore as a centre.

Ask C.S.D. to arrange for the manufacture of ten conveyors to the new designs and to issue them to Comdt. S.A.S. (Hythe) for trials. Priority P*.
5. Ask Comdt. S.A.S. (Hythe) to carry out further trials with the new conveyors. Ask him to return the conveyors now with him to C.S.D. (Enfield Lock).
Forward to C.I.S.A A. for information.

No. 6,783 .See 7598                                      611c
2701 Ammunition/ 47         12.6.40
103/0/17             RIFLES.
110/1/3/1             Boys 0.55 inch.
110/1/14/1             Parker Hale conveyors for sub-calibre firing.
F        Previous No. 6,016.
D. of A., 13. 5. 40, to M.T.2 (re No. 6,016).
If this simple training device for 0.55 inch Boys A/T rifle can be made to work, it will confer many advantages and will be easy to produce and requires no fitting to the weapon like 0.22 inch or air rifles. It may not be possible to attain extreme accuracy with this device, and in view of the simplicity of the device some lowering of the standard may be justified. Will you consider this.
M.T.2, 19. 5. 40, to D. of A.
We consider that this device offers great advantages from the training point of view, and we do not think that absolute accuracy is an essential before it can be adopted.
We consider the standard of a 1 inch group at 15 yards is too high to expect from such a device, the main advantage of which is not that it is entirely accurate, but that it enables practice in firing the A/T rifle to be carried out with the same motion as if the man were shooting full charge ammunition.
We should like to see the results of further trials.
D. of A..(A.3), 25. 5. 40, to See. O.B.
To note remarks by M.T. regarding accuracy in relation to this investigation.
Action.—Noted.
Forward to C.SAD. for information.
27

NO. 7,598                  See 8167                      SECRET.
24.7 40
1.03/0/17                         RIFLES.
110/1/3/1             Boys 0.55 inch.
110/1/14/1             Parker-Hale conveyors for sub-calibre firing.
F        Previous No. 6,783.
C.I.S.A., 11. 7. 40, to Sec. O.B. (re No. 6,016).
Twenty conveyors to the new designs have been submitted by C.S.D. for trial, and accuracy diagrams have been fired at 15 and 25 yards. As the standard of accuracy desired by Comdt. S.A.S. was not obtained at these ranges, trials at greater ranges were not attempted. These conveyors are a good fit in the chamber of a new rifle, but the " bores " are not concentric with the outside of the conveyor and vary from 0.002 to 0.012 inch in eccentricity. Where one conveyor was placed in the chamber in the same position a 5-round diagram of inch x ½ inch at 15 yards range was obtained, which goes to prove that the requisite accuracy is obtainable from. a 4-inch barrel, but we are doubtful if a concentricity of bore greater than that of the samples submitted for trial could be obtained in manufacture.
Thus it would appear that an accuracy figure of a 2-inch group at 15 yards is the best that can be expected from these conveyors.
One round, when feeding from the magazine, struck the barrel face and set up a burr at the muzzle of the conveyor, causing inaccuracy and key-holing with this round. The same thing might. occur as a result of ejection on to a hard floor.
Sixteen. conveyors have been forwarded to Comdt. S.A.S. for trial.

REPORT OF TRIAL.
Date, 10. 7. 40.            Gun.-No. A 5.            Ammunition.-I.C.I. Rim Fire, Mark I.
No. of conveyors used. - 20. (From 0.002 to 0.012 inch eccentric.)

Advanced Action, 19. 7. 40.
Forward to D. of A.
The accuracy obtained with these conveyors shows little improvement on that reported in Proc. No. 6,016.
In normal production it should, in the opinion of the Board, be possible to work to a maximum eccentricity of bore of about 0.0075 inch, even so the size of the rectangle at 15 yards will not be appreciably less than 2 inches square.
By selective loading, i.e., loading each round in the chamber so that the eccentricity is either up or down, a considerably reduced rectangle should be obtained ; and if it is decided to supply these conveyors for training purposes, it is suggested that this pro­cedure should be adopted. To reduce the work carried out by C.I.A., it is suggested that the determination of the best position for each conveyor should be carried out by units, that the " up " position on each conveyor should be marked and that they should subsequently be loaded into magazines in the correct relative position.
Trials are being continued by Comdt. S.A.S., and he has been asked to test this system and report by telephone.
Forward to C.I.A., C.S.D., C.I.S.A. and Comdt. S.A.S. for information.

Action.- 'The Board confirm Advanced Action taken on 19. 7. 40.

No 8,167
21.840
103/0/17                  RIFLES.
110/1/3/1                  Boys 0.55 inch.
1104/14/1                 Parker-Hale conveyors for sub-calibre firing.
LSAE42
F

SECRET

Previous No. 7,598.

S. of E. (Pendine), 3. 8. 40, to See. O.B.

1. The object of this trial was to determine whether the standard of accuracy obtained was satisfactory :—

(a). With no " selective" loading,
(in. With " selective " loading,
i.e., loading conveyors always in the same relative position in the maga­zine, so that the same given point on the circumference always came uppermost in the breech.
In regard to (a), 0.C. Hythe Wing S.A.S. confirms that the standard of accuracy obtained in the trial is acceptable, and in these circumstances it does not appear necessary to introduce (b) .
In any case, it Would be undesirable to introduce further complication in training in respect of selective loading, for which conveyors would presumably have to be " matched " by trial and error on the range.

1. The question of training expedients to supplement full charge firing with the 0-55 inch Boys has been the subject of much controversy since the rifle was introduced (S.A.C. Minute 1,628, .dated, 13. 1. 37, refers).

It is agreed that nothing can replace full charge firing. Even the aluminium bullets for use on classification ranges would not obviate the necessity for completing training with full charge firing.
Supply questions involving wear of barrels as well as provision of ammunition can hardly be disregarded.
In regard to barrel wear, the following gauging records of guns used in this estab­lishment, and since exchanged, may be of interest :-
Barrel gauging.

It is not possible to give a reliable indication of the effect of the above records of wear on M.V., since delay was experienced in obtaining reliable cordite W Mark I and cordite W Mark IT ammunition for control purposes, but it may be accepted that 1000-1500 rounds with cordite W Mark I or cordite W Mark II ammunition will result in barrel wear, which will appreciably affect performance.
Report by E.L.O. S.A.S., dated 29. 7. 40.
Information.
Received sixteen 0-55 inch / 0.22 conveyors by Parker-Hale for trial.
The Board instructed by telephone that great care should be taken to test the con­veyor in various relative positions in the barrel.

Method.
The C.O. Hythe Wing agreed to accept any reasonable grouping capacity. The following trials, therefore. were staged, using four rifles
Trial 1.      Stationary target, 200/25.
Grouping at 10 yards.
15 „
25
Expert firers.
Trial 11. Stationary tank target, 1/30th scale.
Application at 10 yards.
15 „,,
    20 „
25 „
Expert firers.
Trial Ill. Repeat trial II at moving target. 1/30th scale.
Expert firers.
Trial TV. Repeat trials II and III with troops.
The trials to be conducted in a miniature range.
This was a covered range and climatics can be ignored.
The troops employed were tyro soldiers, having no knowledge of the weapon beyond elementary aiming.
Check groups were fired by Officer and N.C.O. instructors in trial IV.
Results