Principles of Ammunition (1910)
THE SHELL.
Field Artillery projectiles are either shrapnel or high-explosive shell. Common shell and case-shot may now be considered obsolete.
Shrapnel. …The walls of the shell are made as thin as possible, in order to get in the greatest possible weight of bullets. For this reason, the shell is made of hard and tough nickel steel, pressed hot from the ingot and afterwards drawn out hot by passing through successive discs.
It will be observed that the body of the shell is contracted at the shoulder. The object of this “choke-boring” is to get a closer pattern with the bullets, the idea being that the outer ring of bullets get an inward impulse from the incurved shoulders of the shell which reduces their centrifugal velocity. The soundness of this theory has not been conclusively proved. This form of body, however, gives facilities for getting the greatest number of bullets into the shell, and the makers consider this a sufficient reason for adopting it.
The diaphragm separating the powder from the bullets is steel drop-forging, and is flat instead of conical so as to give the minimum dispersive effect on the bullets. It is supported by a shoulder in the wall of the shell, into which it fits tightly. There is not tin up to contain the burster, but the powder-chamber has a smooth internal coating of lacquer.
The curve of the head and shoulder of the shell is struck with a radius of 2.3 diameters, this shape of shell being found to keep up its velocity much better than one with a head of only 1-1/2 diameters. The latest pattern of Russian shrapnel has a head struck with a radius of no less than 2.75 diameters, and the St. Chamond shell shown in the Plate have 3-diameter heads.
The principal objection to these extra long heads is the loss of a bullet capacity which results from their use. It is estimated that a 15-pr. shell with a 2-diameter head holds 8 more bullets (42 to the lb.) than shell of the same total weight with head struck with 3-diameter radius.
A smoke-producing charge of 1-3/4 oz. of coarse black powder is poured in among the bottom bullets, and the bullets are consolidated by pressure, a dead-weight pressure of 10 tons being applied three times during the filling of the shell. The object of this is first to prevent prematures, due the grinding of the smoke-produce between the bullets on discharge, by consolidating the bullets so that they cannot move; and in the second place, to get the maximum number of bullets into the shell.
The bullets are further secured by pouring melted resin into the interstices….
On inspecting the illustration already given of a field shrapnel, it will be noticed that a large proportion of the available space is taken up by the driving charge of 3 oz. black powder. Now since smokeless powder occupies a much smaller space than an equivalent charge of black powder, it would appear desirable to use cordite or ballistite in the powder chamber of a shrapnel shell. If the powder chamber could be cut down to half its height a considerable shaving in weight would be effected, which could be utilized in providing an increased number of bullets. The smoke-producer would then occupy the interstices between the bullets, so that no space would be wasted.
Several attempts have been made to realise this ideal, but the results have not so far been encouraging. The trouble is that the smokeless powder, when closely confined in a chamber at the bottom of a shell, detonates or partly detonates instead of burning quietly. The effect is occasionally to blow off the base of the shell, but usually to break up the shell violently, to become a practical fact.
Source: Brevet-Colonel H. A. Bethell, Royal Field Artillery, Modern Guns and Gunnery, 1910: A Practical Manual for Officers of the Horse, Field and Mountain Artillery, F. J Cattermole, Woolwich, England, 1910, pp. 154-56. Image: P. 84.