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.
7.92×33mm Kurz The 7.92×33mm "Kurz (designated as the 7.92 x 33 kurz by the C.I.P.) is a rimless bottlenecked intermediate rifle cartridge developed in Nazi Germany prior to and during World War II. The ammunition is also referred to as 7.9mm "Kurz ("German: "Kurz" " meaning "short"), 7.9 "Kurz", or 7.9mmK, or 8×33 Polte. It was specifically intended for development of an automatic carbine (assault rifle). The round was developed as a compromise between the longer 7.92×57mm rifle and the 9×19mm Parabellum pistol rounds, and is known as an intermediate cartridge (German: "Mittelpatrone" ).