When the Soviets adopted the Kalashnikov 7.62 mm rifle, they abandoned their submachine guns, but in later years realized that they had been a little too hasty and needed a more compact weapon for occupants of vehicles.
Their first attempt was to shorten the AK47 rifle, but this proved to be almost uncontrollable at the automatic fire. At about this time they adopted 5.45 mm caliber for a new generation of Kalashnikov rifles and machine guns, and shortly afterward set about making a compact model in a new caliber. The result was the AKS-74U, which was first revealed to the West in 1982 when a specimen was captured in Afghanistan.
The AKS-74U retains the basic method of the operation of the familiar AK47 rifle, using a gas piston and a rotating bolt, but the shortening of the barrel introduced several complications. The 5.45 mm cartridge was designed to be fired in a long-barrelled rifle, and the gas system of the Kalashnikov taps its gas from a position about two-thirds of the way up the barrel. Since the AKS-74U barrel is so short, all the gas generated in the cartridge would not have time to expend its energy and there would be a prominent muzzle flame and considerable blast. Therefore, a bulbous muzzle attachment can be seen, which acts as an expansion chamber for the emerging gas and muffles the flash and blast. It also helps to balance the internal pressure so that it is possible to tap off the gas for the gas system closer to the breech than in other weapons.
A skeleton butt is fitted, which folds to the left side of the weapon, reducing the overall length to about 16.5 inches. The magazine is similar to that used with an AK47 rifle, but has strengthening ribs molded into its front edge and is made of a lamination of sheet steel and plastic material. The receiver top cover is hinged to the gas block and lifts to permit stripping the weapon; this differs from all other Kalashnikov designs, in which the top cover lifts off completely.
The AKS-74U is an ingenious design but in many eyes somewhat over-powerful for the self-defense role for which it is intended. However, it does mean that the design and operation are already familiar to any soldier who knows the AK series of rifles – which was every Soviet soldier – and, unlike submachine guns, it does not require its own particular type of ammunition, happily firing the standard rifle cartridges.