The SIG SG 540 is a series of Swiss gas-operated assault rifles available in fixed and folding butt stock models, chambered for the 5.56 mm or 7.62 mm NATO cartridge fed from a 20- or 30-round box magazine and with a cyclic rate of between 650 and 800 rounds-per-minute. The muzzle velocity varies between the models from 820 metres per second in the...