Firearm a battle rifle such as the Karabiner 98k, but the chief differences defining an assault rifle are select-fire capability and the use of a rifle round of lesser power, known as an intermediate cartridge. Soviet engineer Mikhail Kalashnikov quickly adapted the German concept, using a less-powerful 7.62×39mm cartridge derived from the standard 7.62×54mmR Russian battle rifle round, to produce the AK-47, which has become the world's most widely used assault rifle. Soon after World War II, the Automatic Kalashnikov AK-47 assault rifle began to be fielded by the Soviet Union and its allies in the Eastern Bloc, as well as
AK-74 variant of the AK-74—the AK-74M (M—Russian: "Модернизированный"; "Modernizirovanniy" or "modernized") assault rifle that offers more versatility compared with its predecessor. Apart from several minor improvements, such as a lightened bolt and carrier assembly to reduce the impulse of the gas piston and bolt carrier during firing, the rifle features a new glass-filled polyamide stock that retains the shape of the original AK-74 fixed laminated wood stock, but side-folds to the left like the skeletonized AKS-74 buttstock. Additionally the AK-74M features an improved muzzle device, a reinforced smooth dust cover and a redesigned guide rod return spring retainer that allows firing