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-47 the rifle to semi-auto. To set the AK-47 to full-auto requires the deliberate action of centering the selector lever. To operate the fire selector lever, right handed shooters have to briefly remove their right hand from the pistol grip, which is ergonomically sub-optimal. Some AK-type rifles also have a more traditional selector lever on the left side of the receiver just above the pistol grip. This lever is operated by the shooter's right thumb and has three settings: safe (forward), full-auto (center), and semi-auto (backward). The AK-47 uses a notched rear tangent iron sight calibrated in increments from . The