SIG-556

The SIG 556 is a semi-automatic rifle produced by SIGARMS International (now known as SIG Sauer Arms Corporation). It was announced in 2006 as a rifle for civilian and law-enforcement use, and was intended primarily for the US market. The SIG 556 is based on the SIG SG 550 assault rifle still in use by the Swiss army today. In the Swiss Army, it is designated as the ‘Stgw 90’ or ‘Sturmgewehr 90’ (‘SG’ also refers to the word ‘Sturmgewehr’). Unlike the SG 550, the SIG 556 is limited to semi-automatic fire only, thus being legal in most countries that permit civilians to own rifles. SIG Sauer also produces the SIG 556 'SWAT' variant, which has a different butt stock and a 4-rail front handguard. The SIG 556 is a gas-operated rifle, using a short-stroke gas piston located above the barrel to cycle the action. The gas system has a manual gas regulator with two settings, allowing an operator to set the rifle for either 'normal' or 'harsh' conditions. The action is locked using a rotary bolt with two massive lugs. The receiver is redesigned from the original SIG SG 550 rifle, and features a stamped steel upper mated to an aluminum alloy lower. The lower receiver houses the trigger group and a redesigned magazine well accepting all M16/AR-15 magazines. A bolt stop device is incorporated into the design, locking the action open on an empty magazine. The manual safety is ambidextrous and located above the pistol grip. The rifle is shipped with a standard 30-round magazine. In its basic configuration, the SIG 556 has no iron sights, with adjustable folding iron sights being an optional extra. The top of the receiver is fitted with a Picatinny rail for easy installation of various optics and sights. Additional attachment rails are installed on the front end of the rifle, at the 3-, 6-, and 9-o’clock positions. The buttstock is of a non-folding, telescoped, adjustable design.