Which riffle on which SIG SG 550 is based is a 5.56×45mm NATO assault rifle developed in the early 1970s by Schweizerische Industrie Gesellschaft?
SIG SG 540 The SG 540 is a 5.56×45mm NATO assault rifle developed in the early 1970s by Schweizerische Industrie Gesellschaft (SIG, currently SAN Swiss Arms AG) based out of Neuhausen, Switzerland as a private venture primarily destined for export markets and as a potential replacement for the 7.5×55mm Swiss SG 510 automatic rifle known as the Stgw 57 in Swiss service.
General-purpose machine gun A general-purpose machine gun (GPMG) is an air-cooled, fully automatic, belt-fed weapon with a quick change barrel that can be used in a variety of roles, from bipod- or tripod-mounted infantry support, to deployment as a helicopter door gun, or a vehicle-mounted support weapon. Modern GPMGs fire full-powered rifle cartridges such as the 7.62×51mm NATO, 7.62×54mmR, 7.5×54mm French, 7.5×55mm Swiss, 7.92×57mm Mauser, etc.