AK-47 was recognized as being simple to operate, rugged, reliable under trying conditions, and amenable to mass production. Built around a 7.62-mm round with a muzzle velocity of some 700 metres per second, it had a cyclic firing rate of 600 rounds per minute and was capable of both semiautomatic and automatic fire. A long curved box magazine held 30 rounds, and a separate gas-return tube above the barrel held a piston that was forced back upon firing to activate the mechanisms that ejected the spent cartridge and cocked the hammer for the next round.