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 550 The SG 550 is an assault rifle manufactured by Swiss Arms AG (formerly a division of Schweizerische Industrie Gesellschaft now known as Sig Holding AG) 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). 
Mannlicher M1895 The Mannlicher M1895 (German: "Infanterie Repetier-Gewehr M.95" , Hungarian: "Gyalogsági Ismétlő Puska M95" ; "Infantry Repeating-Rifle M95") is a bolt-action rifle, designed by Ferdinand Ritter von Mannlicher that used a refined version of his revolutionary straight-pull action bolt, much like the Mannlicher M1890 carbine. It was nicknamed the "Ruck-Zu(rü)ck" (German slang for "back and forth") by Austrian troops and "Ta-Pum" by Italian troops who even wrote a song about it during World War I.