SIG SG 550

SIG 550
SIG 550
Type	Assault rifle
Place of origin	Switzerland
Service history
In service	1986–
Used by	Switzerland, Chile, Indonesia, France, Spain some federal agencies in United States
Production history
Designed	1970s
Manufacturer	Swiss Arms AG (formerly SIG Arms AG
Specifications
Mass	4.05 kg (without magazine)
Length	998 mm (stock open) 772 mm (stock folded)
Barrel length	528 mm (20.8 in)
Cartridge	Gw Pat.90 5.6 mm, 5.56 x 45 mm NATO
Action	Gas operated, rotating bolt
Rate of fire	700 round/min
Muzzle velocity	905 m/s nominal; 895 m/s chronographed
Effective firing range	600 m (~650 yd)against man-size targets; 1.000 m (~1.100 yards) area fire
Maximum firing range	600 m
Feed system	5/10/20/30-round detachable box magazine
Sights	rotating drum with four ranges (close combat and night, 200 m, 300 m, 400m), built-in tritium sight for night aiming

The SIG 550 (Sturmgewehr 90) is an assault rifle manufactured by Swiss Arms AG (formerly SIG Arms AG) of Switzerland. It is considered to be one of the most accurate mass-produced assault rifles available, at the cost of a heavier weight and longer length, when compared to most of today's 5.56mm rifles, which could disadvantage its user in CQB. Standard features include an integral folding bipod and a folding stock. The rifle has an AK-47-type action, and is also known as Fass 90 (Fusil d'assaut 90) in French or as Stgw 90 in German (Sturmgewehr 90).

As of 2007, the SIG 550 is the standard service rifle of the Swiss Armed Forces and it is also offered for export.

The Chilean Army's main assault rifle is the SIG 550 (also with the M-16 rifle and Heckler & Koch G3). The G3 will be replaced by the Heckler & Koch G36 rifle in 2007.

The SIG 551 carbine variant of this rifle has been adopted by various U.S. federal agencies because of its reliability and accuracy, as well as by Special Forces all over the world.

An interesting feature of all SIG 550/551/552 rifles are that they are all equipped with semi-transparent plastic magazines, which are shaped so they may be locked together in order to facilitate faster reloading. The muzzle also features a metallic piece whose purpose is to retain rifle grenades prior to firing.

Development

It was developed as a competitor for the Swiss Army assault rifle contest of 1979 to 1980 and was derived from the previous SIG 540 and SIG 541 models replacing the SIG 510 which is now rare in Swiss service. The SIG 550 won the competition in 1983 and was renamed the Sturmgewehr 90 in German ("Stgw 90") and F ass 90 (for Fusil d'assaut) in French and Italian among the Swiss Army service. However, due to financial constraints, large scale production only began in 1986. From then on, it gradually replaced the older SIG 510 ("F ass 57" or "Stgw 57"), which is now no longer in active service.

Cartridge

The SIG 550 uses the Gw Pat.90 5.6 mm ammunition designed for nominal use at 300 metres [1]. The GW Pat.90 round is dimensionally the same as, and generally interchangeable with 5.56 x 45 mm NATO ammunition, however it is optimized for the SG 550's rifling twist rate of 1 in 10 as opposed to the 1 in 7 for which the 5.56 NATO calibre is optimised and as such provides better performance in the SG 550. It is also slightly heavier than a NATO standard 5.56. The rifle uses 20-round or 30-round magazines. The SG 550 is accurate out to 400 metres without optics (600 metres with optics).

Variants

• SIG 500 SP - A civilian semi-automatic export version of the SIG 550 (called the Sturmgewehr 90 PE when it is sold in Switzerland).
• SIG 550 Sniper - A sniper variant, for use by military marksmen and police/anti-terrorist units. The SG 550-1 Sniper is being delivered with a scope by default.
• SIG 551 - A carbine version with a shorter barrel; it cannot fire rifle grenades.
• SIG 551 SP - A civilian semi-automatic export version of the SIG 551.
• SIG 551 SWAT - A version of the SIG 551 intended for law enforcement purposes; it is equipped with accessory rails on the forestock and comes with a Trijicon ACOG optical sight and a cheekpad on the buttstock.
• SIG 551 LB - A version of the SIG 551 with a longer barrel intended for firing rifle grenades.
• SIG 552 - A commando version (an even shorter version than the SIG 551 with a shorter handguard and an even shorter barrel).
• SIG 556 - A civilian legal semi-automatic carbine made in the United States. Has a Picatinny rail for mounting optics and pop-up manual sights.

Gallery

• 
  with bipod extended
• 
  Disassembled
• 
  With bayonet
• 
  stock folded
• 
  Loaded semi-transparent plastic magazines. The two round protuberences are male parts of the system which allows to locks several magazines together (female parts are on the other side)
• 
  SIG 552, commando version with accessories.
• SIG 551 carbine version
  SIG 551 carbine version
• 552 variant with 4x scope and front grip
  552 variant with 4x scope and front grip

See also

• SIG 552, the most compact variant of the SIG 550.
• Assault rifle
• Gun politics in Switzerland

References

• règlement 53.96 Fusil d'assault 5,6 mm 1990

External links

• Swiss Arms AG site
• Photo array and info on the SIG SG
• SG 550 Manual in PDF format