Caseless ammunition

Caseless ammunition is a type of small arms ammunition that eliminates the cartridge case that typically holds the primer, propellant, and projectile together as a unit.

Caseless ammunition is an attempt to reduce the weight and cost of ammunition by dispensing with the case, which is typically precision made of brass or steel, as well as to simplify the operation of repeating firearms by eliminating the need to extract and eject the empty case after firing. Its acceptance has been hampered by problems with production expenses, heat sensitivity, sealing, and fragility. Its use to date has been limited to prototypes and low-powered firearms.

During World War II, Germany began an intensive program to research and develop a practical caseless ammunition for military use, which was driven by the rising scarcity of metals, especially copper used to make cartridge cases. The Germans had some success, but not sufficient to produce a caseless cartridge system during the war. Japan successfully developed the Ho-301 40mm autocannon during the war for mounting on aircraft. It saw active, though relatively limited, use in the defence of the Japanese home islands during the waning months of the war.

Modern caseless ammunition consists of a solid mass of propellant, originally nitrocellulose, cast into shape to form the body of the cartridge, with cavities to accept the bullet and a primer, preferably combustible, which are glued into place. The completed cartridge might also contain a booster charge of powdered propellant to help ignite the body and provide initial thrust to the bullet.

Many caseless cartridges are also telescoped, with the bulk of the bullet held within the body of the cartridge, to cut down on cartridge length. A shorter cartridge cuts down on the distance the firearm's action must reciprocate to load a new round, which allows for higher cyclic rates and greater probability of multiple hits on a target at long range. Lack of a case also reduces the weight of the cartridge substantially, especially in small bore rifles. For example, the caseless ammunition designed by Austrian inventor Hubert Usel for the Voere VEC-91 weighs about one third as much as regular ammunition for the same caliber.

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