High Quality Content by WIKIPEDIA articles! The SG 550 is an assault rifle manufactured by Swiss Arms AG (formerly Schweizerische Industrie Gesellschaft) of Neuhausen, Switzerland (SG is an abbreviation for Sturmgewehr, or "assault rifle"). The rifle is based on the earlier 5.56mm SG 540 and is also known as the Fass 90 (Fusil d`assaut 90 / Fucile d`assalto 90) in French / Italian or Stgw 90 in German (Sturmgewehr 90).