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.
FN FAL The FN FAL (French: "Fusil Automatique Léger" , English: Light Automatic Rifle), is a battle rifle designed by Dieudonné Saive and Ernest Vervier and manufactured by Fabrique Nationale d'Herstal (FN Herstal). During the Cold War it was adopted by many North Atlantic Treaty Organization (NATO) countries, with the notable exception of the United States. It is one of the most widely used rifles in history, having been used by more than 90 countries.