The SIG 550 (Sturmgewehr 90), manufactured by Swiss Arms AG of Switzerland (formerly SIG Arms AG) is an assault rifle.
The SIG 550 is consistently referenced as one of the most accurate mass-produced assault rifles on the market, at the cost of longer length and a heavier weight, compared against most of today's 5.56mm rifles. This fact could disadvantage its user in CQB. Key standard features include a folding stock and an integral folding bipod. The rifle is known as Stgw 90 in German (Sturmgewehr 90) and Fass 90 (Fusil d'Assaut Standard Suisse 90) in French. Additionally, the rifle has an AK-47-type action.
The SIG 550 is the primary service rifle for the Swiss Armed Forces, as of 2006 and it is also offered for export.
The SIG 550 is also the primary assault rifle for the Chilean Army (also with the M-16 rifle and Heckler & Koch G3). The Heckler & Koch G36 rifle will replace the G3 in 2007.
The SIG 551 carbine version of this rifle has been utilized and adopted by numerous U.S. federal agencies because of its accuracy and reliability, as well as by numerous Special Forces all over the world.
A unique feature of all SIG 550/551/552 rifles are that each rifle is equipped with semi-transparent plastic magazines, which are of a certain shape that enables them to be locked together in order to expedite faster reloading. Additionally, the muzzle of this rifle also features a metallic piece for the purpose of retaining rifle grenades prior to firing.