The caseless cartridge

If it is a good idea to use plastic-cased telescoped cartridges to reduce the size and weight of the ammunition load, surely it would be even better to dispose of the cartridge case altogether? This would not only save more weight, it would remove the need for the case to be extracted and ejected, thereby simplifying gun design.

In larger artillery calibres cartridge cases are not normally used. The projectile and propellant are loaded separately and priming arrangements are contained within the mechanism of the breechblock. Obturation - the sealing of the rear of the chamber against gas escape - is achieved by the design of the breechblock.

The artillery solution is not suitable for auto matic weapons, which require the projectile and propellant to be handled as a unit. Various attempts have been made to overcome this problem. There are three basic approaches (all loosely known as 'case^ss'): combustible cases, either with or without metal heads, and entirely caseless cartridges, with the projectile fixed within rigidly moulded propellant. In larger cannon calibres such as tank armament, developments have mainly concentrated on cartridge cases made from combustible material which is burned away as the cartridge fires. This is lighter than metal and greatly reduces the ejection problem, but it is usually still necessary to form the head of the case out of metal in order to achieve obturation.

The completely combustible telescoped case came very close to adoption in the early 1970s, as part of the 25mm GAU-7/A rotary cannon intended for the F-15 fighter. Several years of development were ended when the project finally ran out of time with the introduction of the F-15. The gun worked well enough, but the ammunition suffered from inconsistent performance because it proved impossible to isolate the propellant from variations in atmospheric temperature and humidity conditions.

The most radical development for a very long time is the new Mauser RMK 30, which uses combustible-cased telescoped 30mm rounds which are front-loaded into a three-chamber revolver cannon, whose design allows for much of the gun gas to be deflected to the rear thereby cancelling most of the recoil. This enables a powerful weapon to be mounted in light helicopters and AFVs which would find it difficult to cope with the recoil forces of a conventional weapon of equivalent power. In the past, most recoilless weapons have been less powerful than their conventional equivalents, but by using advanced propellant technology Mauser have demonstrated muzzle energy comparable with that of the redoubtable GAU-8/A. The gun is intended for the German version of the new European attack helicopter.

There have been many attempts to achieve a different approach in which the cartridge case is dispensed with entirely, the propellant being formed into a hard substance in which are buried the projectile and primer. There are many problems with this approach: how to obtain obturation, how - to make the cartridge tough and weatherproof, how to stop it 'cooking off (i.e. being fired by the heat in the chamber after a long firing session). In the small-arms field. Heckler and Koch of Germany overcame all of them and their caseless 4.7mm G11 rifle was being prepared for production when the end of the Cold War put a brake on military expenditure. While there has so far been no comparable success in larger calibres, there can be little doubt that the future will see the first major change to the military cartridge case in over a century, and may eventually witness its disappearance.

A possible final stage of the process may be to dispose of the concept of a cartridge altogether, in favour of injecting liquid propellant into the chamber the instant before firing. This will permit even simpler ammunition handling, with only the projectiles to be loaded. Its attractions are such that active development work is proceeding with the aim of introducing it into next-generation artillery systems. However, there are currently considerable technical problems.

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