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| SG 550 | |
|---|---|
 The SIG SG 550 | |
| Type | Assault rifle (SG 550) Carbine (SG 551, SG 552 and SG 553) Sniper rifle (SG 550-1 Sniper) |
| Place of origin | Switzerland |
| Service history | |
| In service | 1990–present |
| Used by | SeeUsers |
| Wars | War in Afghanistan (2001–2021) Sinai insurgency 2013 Lahad Datu standoff[1] Yemeni Civil War (2014–present) |
| Production history | |
| Designer | Schweizerische Industrie Gesellschaft |
| Designed | 1970s–1980s |
| Manufacturer | SIG Sauer AG (formerlySchweizerische Industrie Gesellschaft and Swiss Arms) |
| Produced | 1986–present |
| No. built | 600,000 |
| Variants | SeeVariants |
| Specifications | |
| Mass | 4.1 kg (9.04 lb) |
| Length | 1,000 mm (39.4 in) (stock extended) 772 mm (30.4 in) (stock folded) |
| Barrel length | 528 mm (20.8 in) |
| Cartridge |
|
| Action | Gas operated,rotating bolt |
| Rate of fire | ~700 rounds/min |
| Muzzle velocity | 911 m/s (2,989 ft/s) |
| Effective firing range | 100–400 m sight adjustments |
| Feed system |
|
| Sights | Rear: rotating diopter drum withtritium night inserts; front: hooded post with folding night post 540 mm (21.3 in) sight radius (SG 550) |
TheSG 550 is anassault rifle manufactured bySIG Sauer AG (formerly a division ofSchweizerische Industrie Gesellschaft, now known as SIG Holding AG) in Switzerland. "SG" is an abbreviation forSturmgewehr ("assault rifle"). The rifle is based on the earlier5.56×45mm NATOSIG SG 540.
In 1978, theSwiss armed forces formulated requirements for a successor to theStgw 57battle rifle (known commercially as the SG 510) using the7.5×55mm GP 11cartridge. Emphasis was placed onmodularity; the weapon family was to include several variants of the base design, including a compactcarbine that would be issued to rear-echelon and support troops, command staff, vehicle crews,special forces personnel andparatroopers. Another aim was to reduce the overall weight of the rifle while retaining comparable or improved accuracy out to 300 m. The solicitation was narrowed down to two designs: theW+F C42 (developed by the state-ownedWaffenfabrik Bern, using both 6.45×48mm and 5.56×45mm cartridges) and the SG 541 (developed by SIG using theSG 540 as the basis for the SG 541 prototype). In 1981, the experimental6.45mm GP 80 cartridge was rejected in favor of the more conventional SIG5.6×45mm Gw Pat 90 round (with a 4.1 g,tombac-jacketed,lead core projectile) that is the Swiss equivalent toNATO's standard 5.56×45mm cartridge.
In February 1983, the decision to adopt the SG 541 was publicly announced (the designation of the rifle was changed in October of the following year to SG 550, while the carbine version became known as theSG 551). Production began in 1986 and four years later the rifle was officially accepted into service in 1990, hence the military designation Stgw 90. Over 600,000 rifles have been delivered since then and production for the military has now ceased.[2]
The SG 550 is aselective-fire 5.56×45mm NATOassault rifle firing from aclosed bolt. It has agas-actuated piston-drivenlong-stroke operating system derived from theSIG SG 540 series of rifles, which uses burnt powder gases vented through a port in thebarrel to power the weapon's moving parts. Once inside the gas cylinder, propellant gases pass through an L-shaped channel machined in the piston head and are directed forward towards the gas valve. The pressure build-up in front of the piston head pushes the piston and bolt carrier rearward. As the piston is driven back, the gas port and the L-shaped channel move out of alignment, cutting off the supply of gas to the cylinder. Surplus gas and powder residues are evacuated through an exhaust port in the gas cylinder. The manually adjustable gas valve has two settings, one for normal operation, and the second setting for use in the presence of heavy fouling or icing.
Therotary bolt locking mechanism consists of two steel locking lugs that engage locking recesses in the breech, and is identical to that used in the SG 540. A spring-loadedextractor is incorporated into the bolt while a fixed protrusion on one of the receiver's internal guide rails ejects the spent cartridge casings.
The rifle is hammer-fired and has a trigger mechanism with anambidextroussafety andfire selector switch that has 4 settings: "S"—safe, "1"—single fire, "3"—3-roundburst and "20"—fullyautomatic fire. The 3-round burst mode "3" and the fully automatic "20" position can be disabled by a rotating safety guard to avert accidentally activating the continuous fire mode. Thetrigger is enclosed in a pivoting trigger guard which can be folded down to the left or right side allowing for unhindered operation with winter gloves. The trigger pull is approximately 35 N (7.9 lbf).[3]
The firearm is fed by lightweight 20-round box magazines, 30-, 10- and 5-round magazines are also available. The magazines aremolded from a translucent polymer and can be locked together using studs in order to facilitate quicker reloading (Jungle style). The empty weight of a 20-round magazine is 95 g (3.4 oz) and 110 g (3.9 oz) for a 30-round magazine.
A bolt hold-open device locks the bolt carrier assembly open after expending the last cartridge from themagazine and is released by lifting the bolt catch lever located on the left side of thereceiver. Alternatively, a left-handed shooter may release the bolt by pulling the rubber-coated charging handle to rear a short distance.
The SG 550 has a side-folding skeletonizedbuttstock (folds to the right side of the receiver) and alightweight aluminiumbipod that folds into grooves in the lower handguard. The hinged stock is firmly locked in the folded position by a socket in the butt which clips into a plastic stud on the handguard; a firm pull will release the stock which is then swung into the closed position and locked by a button catch. A collapsible side-folding stock is also available. The stock,pistol grip, and handguards are made of a high-strengthpolymer, and are produced in either green or black colour options. Thesteel receiver housing and several other components are manufactured using stamping and welding; external steel surfaces are finished with a ceramic-reinforced enamel coat known as Ilaflon.[4]
The heavy, cold hammer-forged barrel is screwed into the receiver and is equipped with a slotted "bird cage" typeflash suppressor that is also used to launchrifle grenades (using standard, liveammunition) or attach a knifebayonet (the bayonet is supported by a lug located at the base of the gas block). The rifled barrel has 6 right-hand grooves and the Swiss Army specification 254 mm (1:10 in) rifling twist rate is optimized for Swiss military GP 90 ammunition. An export-oriented5.56×45mm NATO barrel configuration with a 178 mm (1:7 in) twist rate is also available, to adequately stabilize the relatively long NATO L110/M856 5.56×45mm NATO tracer projectile.[5]
All rifles aretest fired for accuracy and function prior to leaving the factory at the manufacturer's underground 300 m test range. Random new rifles out of production were tested on a machine rest. In a 24 single shot string starting with a cold weapon and using GP 90 ammunition, the R50 or 50%windage andelevation dispersion of any individual weapon must have been within an 11 cm (4.3 in) group at 300 m, the 50% windage and elevation dispersion must have averaged 7 cm (2.8 in).[6] The employedcircular error probable method cannot be converted and is not comparable to US military methods for determining rifle accuracy. When the R50 results are doubled the hit probability increases to 93.7%.
The gas system's components are made ofstainless steel. The barrel, bolt, bolt carrier, and firing pin are all made with steel that has beengas nitrided, hardened and tempered. The bolt and carrier, along with most other components internal to the receiver undergo aphosphating process.
The SG 550 series rifles have a 540 mm (21.3 in) long sight radius and are equipped withiron sights adjustable for both windage and elevation. The sights are similar to those on someHeckler & Koch weapons, such as theHK G3 orHK MP5. The sights consist of a rear, rotatingdiopter drum soldered to the receiver and a hooded front post installed in the gas block. The rear sight has an open notch setting marked "1" designed for immediate firing up to 100 m but also contains apertures with settings "2", "3" and "4" corresponding to 200, 300 and 400 m firing ranges. The 400 m setting has a removable iris for sportive shooting. The sights are adjustable via micrometer screws with windage and elevation increments of 0.15mil (≈0.52moa), or 15 mm (0.6 in) at 100 m. For night use, the dedicated "1" notch setting in the rear sight drum is provided with two self-luminoustritium-powered inserts fitted laterally on each side of the notch and additionally in a flip-up post attached to the foresight. When firing rifle grenades the front sight hood is aligned with the uppermost edge of the grenade's warhead, this provides an estimated point of impact up to 75 m. The rifle grenades intended for this purpose were FN/Luchaire Type 58-N bullet-thoughanti-tank grenades.
For designated marksman use, the SG 550 is equipped with a Kern 4×24telescopic sight on a quick-detachable mount.[citation needed] The sight weighs 730 g (26 oz) and includes a variety of features, such asSTANAG 2324/MIL-STD-1913 compliant mounting components, aBullet Drop Compensation (BDC) elevation adjustment knob for ranges from 100 to 600 m, a tritium-illuminatedreticle that enables target acquisition in low-light conditions and a diopter eyesight correction adjustment. Included with the sight is a lens hood for mounting on the ocular that reduces image quality-impairing stray light and a gray filter for glare reduction.[7] The basic model of this optical sight was already used on the Stgw 57.[8]
The upper receiver can accept quick-detachablerails and adapters used to mount optics (STANAG 2324 compliant). Thescope mounting system consists of a centering hole located on the front face of the rear sight assembly and adovetail-like mounting point at the front end of the receiver. Swiss Arms (respectivelyBrügger & Thomet) offer several types of quick-release scope mounts andPicatinny rails. A version of the rifle with an integral receiver-mounted Picatinny rail is also offered; in this configuration the weapon is fitted with flip-up emergency battle sights—a rear aperture sight which folds down into a recess in the rail and a folding front blade.
Both the rifle and carbine come standard with a spare magazine,sling,cleaning kit and a loading aid for rapid magazine filling.
The full-sized SG 550/551 will accept SIG's 40 mmGL 5040/5140grenade launcher (Swiss military designation: 40 mmGewehraufsatz 97), which is mounted under the barrel via an eccentric latch and replaces the lowerhandguard. The grenade launcher is a single-shotbreech-loaded weapon that is supplied with a leaf sight that attaches to the rifle's rear sight base and enables accurate firing out to 200 m. The lightweightaluminium launcher weighs 1.7 kg (3.7 lb) unloaded, and is operated independently of the rifle. It can use a wide array of 40×46mm grenades, including extended range high-pressure types and non-lethal baton or anti-riot projectiles. The compact SG 552/553 can be fitted with smaller GL 5340 underbarrel grenade launcher.
An Stgw 90bayonet can also be mounted to the rifle. The bayonet has an overall length of 310 mm and a muzzle ring diameter of 22 mm. The 177 mm long blade is single-edged and it has nofuller. The bayonets are manufactured exclusively for the Swiss Army byVictorinox and in the past byWenger until Victorinox acquired Wenger in 2005. With a proper lug adaptor, the rifle will also accept a NATO-pattern KCB-77 (made originally by Carl Eickhorn ofSolingen,West Germany) or the AmericanM9.[citation needed]
The SG 551 carbine has a short pattern 363 mm (14.3 in) barrel, gas tube and piston compared to the SG 550. The SG 551 series rifles have a 466 mm (18.3 in) long sight radius. The handguards were also changed and the bipod removed. The SG 551 cannot be used with a bayonet or fire rifle grenades. The SG 551 comes in several specialized variants designed for use with security and special forces. Among those variants are:
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The compactSG 552 Commando (full designation as the 552-2P[9]) carbine was released in July 1998. It has a shorter 226 mm (8.9 in) barrel (with an open, 3-prong flash suppressor) and gas tube, ventilated handguards and a redesigned bolt carrier group that was integrated with the piston rod to form a single moving assembly. The SG 552 series rifles have a 360 mm (14.2 in) long sight radius. The return mechanism has been moved to the rear of the receiver housing and its recoil spring is guided in a way analogous to that of theAK-47: on a steel guide rod (later models feature a polymer guide rod) resting against the lower receiver's rear surface under tension of the compressed recoil spring. Like the SG 550/551, this model can accept rails and accessories enabling the use of optics. A long barrel version of the SG 552 known as theSG 552 LB incorporates a 346 mm (13.6 in) barrel with provision to fire rifle grenades and support a bayonet. The SG 552 models were discontinued in 2008 and replaced by the SG 553. Upgrade part kits are available to convert a SG 552 in to a SG 553.
TheSG 553 is an improved version of the SG 552 and was released in 2008. Even though it mostly resembles the SG 552, the SG 553 has one key advantage, the recoil spring is now wrapped around the piston rod as in the SG 550/551 models, which address several reliability issues encountered in the SG 552 and also allows the usage of the standard SG 550/551 charging handle. The SG 553 series rifles have a 339 mm (13.3 in) long sight radius. A long barrel version of the SG 553 known as theSG 553 LB incorporates a 347 mm (13.7 in) barrel with provision to fire rifle grenades and support a bayonet. Further factory options for the SG 553 rifle series are an integrated receiverPicatinny rail and an adjustable butt stock.[10] TheSG 553 R is a variant chambered for the7.62×39mm cartridge fed fromAK family box magazines.[11] There is also a.300 AAC Blackout variant of the SG 553 known as theSG 553 BK which was first shown atIWA OutdoorClassics in 2016.[12][13]
The SG 552-A1 is a SG 552 rifle that has been modified to function like the SG 553. The modifications are available as a conversion kit that includes a new bolt carrier, charging handle, recoil spring and gas tube.[citation needed]
Another member of the SG 550 family is theSG 550-1 Sniper variant designed at the request of the Swiss Police.[14] Introduced in 1988, This accurized rifle has a refined two-stage trigger (the pull force was reduced from 35 N (7.9 lbf) to 15 N (3.4 lbf), a heavy, hammer-forged 650 mm (25.6 in) long barrel with a 254 mm (1:10 in) rifling twist rate (it has no flash hider) and is used exclusively with telescopic sights. The new folding stock has an adjustable cheek piece and a spacer system on the butt, the ergonomic pistol grip's angle of inclination can be regulated, the forend was shortened, and the bipod features a height and cant adjustment mechanism. This model is no longer in production.
The SG 550/551/552/553 are also available insemi-automatic only configurations, intended for the civilian shooting market. Among these variants are theSG 550/551/552 SP,PE 90 andSIG Sport rifles. The SG 550 series is available with either 178 mm or 254 mm (1:7 and 1:10 in)twist rate barrels. Rifles designated SG 55x-1 have a 254 mm (1:10 in) twist rate, while models marked SG 55x-2 have a 178 mm (1:7 in) twist rate. The ordinance GP 90 ammunition is optimized for use with the original Swiss 254 mm (1:10 in) rifling twist rate.
Due to import restrictions, the American civilian market required a partially American-made version assembled bySIG Sauer, Inc. inExeter, New Hampshire. TheSIG 556 is designed to meet these requirements. The 556 lacks full-auto capability and the overall length is 940 mm (37.0 in). One difference is a newaluminum lower receiver that acceptsM16STANAG magazines and anM4telescoping buttstock. The barrel's twist rate is 178 mm (1:7 in).[15]
There are many variants of this rifle offered for sale. The first variant was sold with an aluminum Picatinny rail on the upper receiver and a series of plastic rails on the handguard. The market pushed SIG to produce the rifle with the slimmer profile 551-type handguards and a hooded front sight; this version is marketed as theSIG 556 Classic.[16] Several folding stock models have been released as well as variants with railed forend combinations. Another variant is theSIG 556 DMR featuring a 18 in (457.2 mm) barrel.[17]SIG P556 pistol variants with 10-inch barrels are also available. In 2012 theSIG 556 R or SIG 556 Russian chambered for the7.62×39mm cartridge and usingAK-pattern box magazines was introduced.[18] The first generation of SIG 556R rifles had a number of performance issues that were later resolved in later production runs of the SIG 556R.
In January 2014, SIG introduced the 556xi series rifles as an improvement to the 556 and 556R series rifles.
As of May 2017, SIG has discontinued the SIG 556, SIG 556R, and 556xi series of rifles and no longer displays those models on the products section of their website.[19]
TheSIG 522LR is a.22-caliber sporting rifle styled after the SG 551. It uses a simpleblowback semi-automatic operating system and its barrel has a 406 mm (1:16 in) twist rate. Due to its operating principle, the rifle has no mechanical commonality with other SG 550 variants. The SIG 522 accepts commonly available AR-style .22-caliber conversion magazines.
In the U.S, a variety of semi-automatic SwissArms firearms are available for sale. Due to U.S. import regulations, they are imported as a pistol.[20]
On 27 February 2014, the Canadian semi-automatic "Classic Green" sporting rifle, also known as the "Swiss Arms PE 90", was re-classified as a "prohibited weapon".[21] The rifle had been popular with hunters and gun enthusiasts, who until February 2014, only required apossession and acquisition licence to obtain the rifle.
In 2013, a gun dealer had imported some PE 90 rifles from Switzerland and brought them to Canada for sale. After some were sold, it was alleged that the rifles in question were of a variant not allowed in Canada (PE90). Upon investigation and examination by the RCMP, this was proven inconclusive, however, the RCMP went further and decided the versions in Canada were too close to the PE90 and reclassified the rifles and declared the entire model line prohibited, with possible confiscation for destruction. This caused outrage amongst owners and lobbyists, who felt that the RCMP exceeded their authority, and that such policy changes should be enacted by legislation.[citation needed]
TheNational Firearms Association of Canada considered pursuit of the matter through the legal system.[22] On 31 July 2015, the Canadian government overturned the reclassification and returned the Swiss rifles to the original classifications.[23]
On 1 May 2020, in the wake of theNova Scotia attacks, the rifles were again reclassified as Prohibited Firearms viaOrder in Council.[24]
