SIG SG 550 (Sturmgewehr 90), Swiss Army service rifle. Gas-operated rotating bolt with 20.8-inch barrel. Type: Rifle Action: Semi-Automatic Caliber: 5.56 NATO Capacity: 30 Year introduced: 1984, Switzerland Weight: 9 oz Overall length: 39.2" Status: Discontinued Military use: Yes Intended use: Military, Collector