View source for SIG SG 550

{{Short description|Swiss Assault rifle}}
{{Use dmy dates|date=April 2022}}
{{More footnotes needed|date=May 2016}}
{{Infobox weapon
| name               = SG 550
| image              = Stgw 90.jpg
| image_size         = 300px
| caption            = The SIG SG 550
| origin             = Switzerland
| type               = [[Assault rifle]] (SG 550)<br /> [[Carbine]] (SG 551, SG 552 and SG 553)<br /> [[Sniper rifle]] (SG 550-1 Sniper)
| is_ranged          = Yes
<!-- Service history -->| service            = 1990–present
| used_by            = See ''[[#Users|Users]]''
| wars               = [[War in Afghanistan (2001–2021)]]<br>[[Sinai insurgency]]<br>[[2013 Lahad Datu standoff]]<ref name="Lahat Datu Standoff">{{cite web |title=The Guns of The Malaysian Police & Military During The Sulu Invasion  |url=https://www.thefirearmblog.com/blog/2013/02/25/the-guns-of-the-malaysian-police-military-during-the-sulu-invasion/ |website=The Firearm Blog |access-date=10 February 2023 |date=25 February 2013}}</ref>
<br>[[Yemeni Civil War (2014–present)]]
| designer           = [[Schweizerische Industrie Gesellschaft]]
| design_date        = 1970s–1980s
| manufacturer       = [[Swiss Arms|SIG Sauer AG]] (formerly [[Schweizerische Industrie Gesellschaft]] and Swiss Arms)
| unit_cost          = 
| production_date    = 1986–present
| number             = 600,000
| variants           = See ''[[#Variants|Variants]]''
<!-- General specifications -->| weight             = {{convert|4.1|kg|lb|2|abbr=on}}
| length             = {{convert|1000|mm|in|1|abbr=on}} (stock extended) <br />{{convert|772|mm|abbr=on|1}} (stock folded)
| part_length        = {{convert|528|mm|abbr=on|1}}
| width              = 
| height             = <!-- Ranged weapon specifications -->
| cartridge          = * [[5.56×45mm NATO]]{{efn|Known as 5.6 mm Gw Pat 90 in Switzerland.}}
* [[7.62×39mm]] (used in SG 553 R variant)
* [[.300 AAC Blackout]] (used in SG 553 BK variant)
* [[6.5mm Creedmoor]] (used in SG 750 variant)
* [[7.62×51mm NATO]] (used in SG 751 variant)
| action             = [[Gas-operated reloading|Gas operated]], [[rotating bolt]]
| rate               = ~700 rounds/min
| velocity           = {{convert|911|m/s|0|abbr=on}}
| range              = 100–400 m sight adjustments
| feed               = *5-, 20-, or 30-round detachable [[box magazine]]
* [[STANAG magazine]]s (SIG 556 series)
* [[AK-47]] magazines (SG 553 R, SIG 556 R)
| sights             = Rear: rotating diopter drum with [[Tritium illumination|tritium night inserts]]; front: hooded post with folding night post<br />{{convert|540|mm|abbr=on|1}} sight radius (SG 550)
}}

The '''SG 550''' is an [[assault rifle]] manufactured by [[Swiss Arms|SIG Sauer AG]] (formerly a division of [[Schweizerische Industrie Gesellschaft]], now known as SIG Holding AG) in Switzerland. "SG" is an abbreviation for ''Sturmgewehr'' ("assault rifle"). The rifle is based on the earlier [[5.56×45mm NATO]] [[SIG SG 540]].

==History==
===Development===
In 1978, the [[Swiss armed forces]] formulated requirements for a successor to the [[SIG SG 510|Stgw 57]] [[battle rifle]] (known commercially as the SG 510) using the [[7.5×55mm Swiss|7.5×55mm GP 11]] [[Cartridge (firearms)|cartridge]]. Emphasis was placed on [[Modular Weapon System|modularity]]; the weapon family was to include several variants of the base design, including a compact [[carbine]] that would be issued to rear-echelon and support troops, command staff, vehicle crews, [[special forces]] personnel and [[paratrooper]]s. 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: the [[W+F C42]] (developed by the state-owned [[Waffenfabrik Bern]], using both 6.45×48mm and 5.56×45mm cartridges) and the SG 541 (developed by SIG using the [[SIG SG 540|SG 540]] as the basis for the SG 541 prototype). In 1981, the experimental [[6.45×48mm XPL Swiss|6.45mm GP 80]] cartridge was rejected in favor of the more conventional SIG [[5.6mm Gw Pat 90|5.6×45mm Gw Pat 90]] round (with a 4.1 g, [[tombac]]-jacketed, [[lead]] core projectile) that is the Swiss equivalent to [[NATO]]'s standard 5.56×45mm cartridge.
[[File:C42 6.45mm Rifle-IMG 0070-b-white.jpg|thumb|The C42 by [[Waffenfabrik Bern]], 6.45mm Rifle version]]

===Production===
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 the '''SG 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.<ref name="SIG SG 550 (Sturmgewehr Model 550) / Stgw 90 Assault Rifle / Carbine June 22, 2014">{{cite web |url=http://www.militaryfactory.com/smallarms/detail.asp?smallarms_id=616 |title=SIG SG 550 (Sturmgewehr Model 550) / Stgw 90 Assault Rifle / Carbine (1990) |date=22 June 2014 |publisher=Military Factory |access-date=24 December 2014 |archive-url=https://web.archive.org/web/20170706024926/http://www.militaryfactory.com/smallarms/detail.asp?smallarms_id=616 |archive-date=6 July 2017 |url-status=live }}{{better source needed|date=January 2019}}</ref>

==Design details==
===Operating mechanism===
[[File:Caroline-demontee-p1000529.jpg|thumb|left|SG 550 disassembled into its main constituent groups]]

The SG 550 is a [[selective-fire]] 5.56×45mm NATO [[assault rifle]] firing from a [[closed bolt]]. It has a [[Gas-operated reloading|gas-actuated]] piston-driven [[Gas-operated reloading#Long-stroke|long-stroke operating system]] derived from the [[SIG SG 540]] series of rifles, which uses burnt powder gases vented through a port in the [[Gun barrel|barrel]] 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.

The [[Rotating bolt|rotary 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-loaded [[extractor (firearms)|extractor]] is incorporated into the bolt while a fixed protrusion on one of the receiver's internal guide rails ejects the spent cartridge casings.

===Features===
[[File:Caroline-pontet-p1000527.jpg|thumb|The rifle controls, including fire selector/safety.]]

The rifle is hammer-fired and has a trigger mechanism with an [[Ambidexterity#Firearms|ambidextrous]] [[Safety (firearms)|safety]] and [[Selective fire|fire selector]] switch that has 4 settings: "S"—safe, "1"—single fire, "3"—3-round [[Burst mode (weapon)|burst]] and "20"—fully [[Automatic firearm|automatic 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. The [[Trigger (firearms)|trigger]] 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 {{convert|35|N|lb-f|1|lk=on|abbr=on}}.<ref>{{Cite web|url=https://www.sigsauer.swiss/en/sg-550-pe-90-assault-rifle.php|title=SG 550 / PE 90 Assault Rifle|website=www.sigsauer.swiss}}</ref>

The firearm is fed by lightweight 20-round box magazines, 30-, 10- and 5-round magazines are also available. The magazines are [[Injection molding|molded]] 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 {{convert|95|g|abbr=on}} and {{convert|110|g|abbr=on}} for a 30-round magazine.

A bolt hold-open device locks the bolt carrier assembly open after expending the last cartridge from the [[Magazine (firearms)|magazine]] and is released by lifting the bolt catch lever located on the left side of the [[Receiver (firearms)|receiver]]. 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 skeletonized [[Stock (firearms)|buttstock]] (folds to the right side of the receiver) and a [[Aluminium alloy|lightweight aluminium]] [[bipod]] 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-strength [[polymer]], and are produced in either green or black colour options. The [[steel]] 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.<ref>{{cite web |url=http://www.ilag-ag.com/cms2/site/user/index.php?page_id=252 |title=ILAG Industrielack AG – Swiss quality coatings |publisher=Ilag-ag.com |access-date=9 July 2009 |archive-url=https://web.archive.org/web/20090516014752/http://www.ilag-ag.com/cms2/site/user/index.php?page_id=252 |archive-date=16 May 2009 |url-status=dead  }}</ref>

The heavy, cold hammer-forged barrel is screwed into the receiver and is equipped with a slotted "bird cage" type [[flash suppressor]] that is also used to launch [[rifle grenade]]s (using standard, live [[ammunition]]) or attach a knife [[bayonet]] (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&nbsp;mm (1:10 in) rifling twist rate is optimized for Swiss military GP 90 ammunition. An export-oriented [[5.56×45mm_NATO#Rifle_barrel_configurations|5.56×45mm NATO barrel configuration]] with a 178&nbsp;mm (1:7 in) twist rate is also available, to adequately stabilize the relatively long NATO L110/M856 5.56×45mm NATO tracer projectile.<ref>{{cite web |url=http://laissezfirearm.info/tracer.htm |title=Some Skinny on the NATO 5.56mm L110/M856 Tracer Round |date=May 1998 |website=LaissezFirearm.info |access-date=2022-02-13|archiveurl=https://web.archive.org/web/20230417101814/http://laissezfirearm.info/tracer.htm|archive-date=April 17, 2023}}</ref>

All rifles are [[Proof test#Firearms|test 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 R<sub>50</sub> or 50% [[windage]] and [[Elevation (ballistics)|elevation]] dispersion of any individual weapon must have been within an {{convert|11|cm|abbr=on|1}} group at 300 m, the 50% windage and elevation dispersion must have averaged {{convert|7|cm|abbr=on|1}}.<ref name="biggerhammer.net">{{cite web|url=http://www.biggerhammer.net/sigamt/550/550techinspection/|title=SIG 550 / 551 Technical Data and Test Documentation|access-date=25 December 2014|archive-url=https://web.archive.org/web/20141231210358/http://www.biggerhammer.net/sigamt/550/550techinspection/|archive-date=31 December 2014|url-status=live}}</ref> The employed [[circular error probable]] method cannot be converted and is not comparable to US military methods for determining rifle accuracy. When the R<sub>50</sub> results are doubled the hit probability increases to 93.7%.

The gas system's components are made of [[stainless steel]]. The barrel, bolt, bolt carrier, and firing pin are all made with steel that has been [[Nitridization|gas nitrided]], hardened and tempered. The bolt and carrier, along with most other components internal to the receiver undergo a [[Parkerizing|phosphating]] process.

===Sights===
[[File:Caroline-mire-p1000518.jpg|thumb|Rotating diopter drum rear sight.]]
[[File:Nightsight.JPG|thumb|right|[[Tritium illumination|Tritium-illuminated]] night sights.]]

The SG 550 series rifles have a {{convert|540|mm|abbr=on|1}} long sight radius and are equipped with [[iron sights]] adjustable for both windage and elevation. The sights are similar to those on some [[Heckler & Koch]] weapons, such as the [[HK G3]] or [[HK MP5]]. The sights consist of a rear, rotating [[Diopter sight|diopter]] 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&nbsp;m but also contains apertures with settings "2", "3" and "4" corresponding to 200, 300 and 400&nbsp;m firing ranges. The 400&nbsp;m setting has a removable iris for sportive shooting. The sights are adjustable via micrometer screws with windage and elevation increments of 0.15 [[milliradian|mil]] (≈0.52 [[Minute of arc|moa]]), or {{convert|15|mm|abbr=on|1}} at 100&nbsp;m. For night use, the dedicated "1" notch setting in the rear sight drum is provided with two self-luminous [[Tritium illumination|tritium-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-though [[anti-tank grenade]]s.

For designated marksman use, the SG 550 is equipped with a Kern 4×24 [[telescopic sight]] on a quick-detachable mount.{{citation needed|date=January 2013}} The sight weighs {{convert|730|g|abbr=on}} and includes a variety of features, such as [[Picatinny rail|STANAG 2324/MIL-STD-1913]] compliant mounting components, a [[Telescopic sight#Bullet drop compensation|Bullet Drop Compensation]] (BDC) elevation adjustment knob for ranges from 100 to 600 m, a tritium-illuminated [[reticle]] 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.<ref>{{cite web|url=http://home.arcor.de/snipercountry/waffen/artikel/waffen12.html|title=[www.snipercountry.de] - Scharfschützen Community|access-date=25 December 2014|archive-url=https://web.archive.org/web/20140714200755/http://home.arcor.de/snipercountry/waffen/artikel/waffen12.html|archive-date=14 July 2014|url-status=live}}</ref> The basic model of this optical sight was already used on the Stgw 57.<ref>[http://www.biggerhammer.net/sigamt/kern/ biggerhammer.net] {{Webarchive|url=https://web.archive.org/web/20070822151929/http://www.biggerhammer.net/sigamt/kern/ |date=22 August 2007 }} Kern 4x24 telescopic sight of the Swiss Army.</ref>

The upper receiver can accept quick-detachable [[Rail system (firearms)|rails]] and adapters used to mount optics (STANAG 2324 compliant). The [[scope mount]]ing system consists of a centering hole located on the front face of the rear sight assembly and a [[dovetail]]-like mounting point at the front end of the receiver. Swiss Arms (respectively [[Brügger & Thomet]]) offer several types of quick-release scope mounts and [[Picatinny rail]]s. 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.

===Accessories===
[[File:Swiss soldier SG550 GL5040.JPG|thumb|right| Swiss soldier with a SG 550 and a GL 5040/5140 grenade launcher]]
[[File:Bayonet SG550.JPG|thumb|right|Stgw 90 bayonet made by Wenger]]

Both the rifle and carbine come standard with a spare magazine, [[sling (firearms)|sling]], [[Firearm maintenance#Cleaning|cleaning]] kit and a loading aid for rapid magazine filling.

The full-sized SG 550/551 will accept SIG's 40 mm [[SIG GL 5040|GL 5040/5140]] [[grenade launcher]] (Swiss military designation: 40&nbsp;mm ''Gewehraufsatz'' 97), which is mounted under the barrel via an eccentric latch and replaces the lower [[handguard]]. The grenade  launcher is a single-shot [[breech-loading weapon|breech-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 lightweight [[aluminium]] launcher weighs {{convert|1.7|kg|abbr=on}} 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 90 [[bayonet]] can also be mounted to the rifle. The bayonet has an overall length of 310&nbsp;mm and a muzzle ring diameter of 22&nbsp;mm. The 177&nbsp;mm long blade is single-edged and it has no [[fuller (weapon)|fuller]]. The bayonets are manufactured exclusively for the Swiss Army by [[Victorinox]] and in the past by [[Wenger]] 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 of [[Solingen]], [[West Germany]]) or the American [[M9 bayonet|M9]].{{cn|date=September 2023}}

==Variants==
===SG 551===
[[File:SIG-551-p1030048.jpg|thumb|right|SG 551 carbine]]

The SG 551 carbine has a short pattern {{convert|363|mm|in|1|abbr=on}} barrel, gas tube and piston compared to the SG 550. The SG 551 series rifles have a {{convert|466|mm|abbr=on|1}} 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:
* '''SG 551-1P''' police carbine, designed to engage point targets out to 300 m; equipped with a Hensoldt 6x42 BL [[telescopic sight]] and detachable cheek riser. 
* '''SG 551 [[SWAT]]''' carbine, coated with a corrosion-resistant finish and equipped with an optical sight mount used with a wide array of sights, and can also accept mission-critical accessories such as a bipod, laser pointer or tactical light.
* '''SG 551 LB''' carbine with an extended {{convert|454|mm|in|1|abbr=on}} barrel that enables the use of rifle grenades and a bayonet.<ref name="SIG SG 550 (Sturmgewehr Model 550) / Stgw 90 Assault Rifle / Carbine June 22, 2014"/>

===SG 552 Commando===
[[File:Exercício Conjunto Meridiano Poti (51670877884).jpg|thumb|right|Brazilian special forces with the SG 551]]

The compact '''SG 552 Commando''' (full designation as the 552-2P<ref>{{cite web|url=http://www.defensereview.com/sig-552-commando-mini-assault-rifle-for-special-operations|title=SIG 552 Commando Mini-Assault Rifle for Special Operations.|author=David Crane|date=28 November 2001|work=DefenseReview.com (DR): An online tactical technology and military defense technology magazine with particular focus on the latest and greatest tactical firearms news (tactical gun news), tactical gear news and tactical shooting news.|access-date=25 December 2014|archive-url=https://web.archive.org/web/20141021192143/http://www.defensereview.com/sig-552-commando-mini-assault-rifle-for-special-operations/|archive-date=21 October 2014|url-status=live}}</ref>) carbine was released in July 1998. It has a shorter {{convert|226|mm|in|1|abbr=on}} 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 {{convert|360|mm|abbr=on|1}} 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 the [[AK-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 the '''SG 552 LB''' incorporates a {{convert|346|mm|in|1|abbr=on}} 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.

===SG 553===
[[File:SIG SG 553 LB.jpg|thumb|right|SG 553 in the hands of [[Malaysian Air Force]] [[PASKAU]] commando during LIMA 2009]]

The '''SG 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 {{convert|339|mm|abbr=on|1}} long sight radius. A long barrel version of the SG 553 known as the '''SG 553 LB''' incorporates a {{convert|347|mm|in|1|abbr=on}} barrel with provision to fire rifle grenades and support a bayonet. Further factory options for the SG 553 rifle series are an integrated receiver [[Picatinny rail]] and an adjustable butt stock.<ref>[http://swissarms2.ath.cx/fileadmin/editor/downloads/infomaterial/Preisliste_2009.pdf Preisliste_2009]{{dead link|date=April 2018 |bot=InternetArchiveBot |fix-attempted=yes }}</ref> The '''SG 553 R''' is a variant chambered for the [[7.62×39mm]] cartridge fed from [[AK-47|AK family]] box magazines.<ref>{{cite web|url=http://www.swissarms.ch/en/SG_553_R.html|title=Swiss Arms: SG 553 R|author=Jürgen Kapella|access-date=25 December 2014|archive-url=https://web.archive.org/web/20141024081544/http://www.swissarms.ch/en/SG_553_R.html|archive-date=24 October 2014|url-status=live}}</ref> There is also a [[.300 AAC Blackout]] variant of the SG 553 known as the '''SG 553 BK''' which was first shown at [[IWA OutdoorClassics]] in 2016.<ref>{{cite web |last1=B |first1=Eric |title=Exclusive: SIG Sauer – Swiss Arms. 300 BLK, 7.62×39 and more… |url=https://www.thefirearmblog.com/blog/2016/05/20/exclusive-sig-sauer-swiss-arms-300-blk-762x39/ |website=The Firearm Blog |date=20 May 2016 |publisher=www.thefirearmblog.com |access-date=19 May 2022}}</ref><ref>{{cite web |title=Assault Rifle SG 553 BK |url=https://www.sigsauer.swiss/en/sg-553-bk-assault-rifle.php |website=www.sigsauer.swiss |publisher=Sig Sauer |access-date=19 May 2022}}</ref>

=== SG 552-A1 ===
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|date=May 2022}}

=== SG 550-1 Sniper ===
Another member of the SG 550 family is the '''SG 550-1 Sniper''' variant designed at the request of the Swiss Police.<ref>{{cite web |last1=McCollum |first1=Ian |title=SIG 550-1 Sniper: Answering a Question Nobody Asked |url=https://www.forgottenweapons.com/sig-550-1-sniper-answering-a-question-nobody-asked/ |website=forgottenweapons.com |date=31 December 2019 |publisher=Forgotten Weapons |access-date=19 May 2022}}</ref> Introduced in 1988, This accurized rifle has a refined two-stage trigger (the pull force was reduced from {{convert|35|N|lb-f|abbr=on|1}} to {{convert|15|N|lb-f|abbr=on|1}}, a heavy, hammer-forged {{convert|650|mm|abbr=on|1}} long barrel with a 254&nbsp;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.

===Civilian variants===
The SG 550/551/552/553 are also available in [[Semi-automatic firearm|semi-automatic]] only configurations, intended for the civilian shooting market. Among these variants are the '''SG 550/551/552 SP''', '''PE 90''' and '''SIG Sport''' rifles. The SG 550 series is available with either 178&nbsp;mm or 254&nbsp;mm (1:7 and 1:10 in) [[twist rate]] barrels. Rifles designated SG 55x-1 have a 254&nbsp;mm (1:10 in) twist rate, while models marked SG 55x-2 have a 178&nbsp;mm (1:7 in) twist rate. The ordinance GP 90 ammunition is optimized for use with the original Swiss 254&nbsp;mm (1:10 in) rifling twist rate.

[[File:Sig 556 Classic.jpg|thumb|A SIG 556 Classic equipped with an [[EOTech]] 512 holographic weapon sight and [[STANAG magazine]].]]

Due to import restrictions, the American civilian market required a partially American-made version assembled by [[SIG Sauer|SIG Sauer, Inc.]] in [[Exeter, New Hampshire]]. The '''SIG 556''' is designed to meet these requirements. The overall length is {{convert|940|mm|in|1|abbr=on}}. One difference is a new [[aluminum]] lower receiver that accepts [[M16 rifle|M16]] [[STANAG magazine]]s and an [[M4 carbine|M4]] [[telescoping stock|telescoping buttstock]]. The barrel's twist rate is 178&nbsp;mm (1:7 in).<ref>{{Cite web|url=https://www.sigsauer.com/|archive-url=https://web.archive.org/web/20070711003756/http://www.sigarms.com/Products/ShowCatalogProductDetails.aspx?categoryid=35&productid=114|url-status=dead|title=SIG SAyer Firearms • Ammunition • Electro-Optics • Suppressors • Airguns • Training|archive-date=11 July 2007|website=www.sigsauer.com}}</ref>

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 the '''SIG 556 Classic'''.<ref>{{cite web|url=http://www.americanrifleman.org/ArticlePage.aspx?id=1661&cid=0|title=American Rifleman |access-date=25 December 2014|archive-url=https://web.archive.org/web/20160118004704/http://www.americanrifleman.org/ArticlePage.aspx?id=1661&cid=0|archive-date=18 January 2016|url-status=dead}}</ref> Several folding stock models have been released as well as variants with railed forend combinations. Another variant is the '''SIG 556 DMR''' featuring a {{convert|18|in|mm|1|abbr=on}} barrel.<ref>{{cite web |title=SIG Sauer 556 DMR Semi Automatic Rifle |url=https://www.cheaperthandirt.com/sig-sauer-556-dmr-semi-automatic-rifle-.223-rem5.56-nato-18-barrel-20-round-capacity-polymer-grip-nitron-x-finish-r556-h18b-dm/FC-798681429554.html |website=cheaperthandirt.com |access-date=19 May 2022}}</ref> '''SIG P556''' pistol variants with 10-inch barrels are also available. In 2012 the '''SIG 556 R''' or SIG 556 Russian chambered for the [[7.62×39mm]] cartridge and using [[AK-47|AK]]-pattern box magazines was introduced.<ref>{{cite web|url=http://www.sigsauer.com/CatalogProductDetails/sig556r.aspx|title=SIG 556R|access-date=25 December 2014|archive-url=https://web.archive.org/web/20141225190557/http://www.sigsauer.com/CatalogProductDetails/sig556r.aspx|archive-date=25 December 2014|url-status=live}}</ref> 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.<ref>{{Cite news|url=https://www.sigsauer.com/full-product-catalog/all-rifles/|title=All Rifles |work=Sig Sauer|access-date=8 May 2017|language=en-US|archive-url=https://web.archive.org/web/20170131030316/https://www.sigsauer.com/full-product-catalog/all-rifles/|archive-date=31 January 2017|url-status=live}}</ref>

The '''[[SIG 522LR]]''' is a [[.22 Long Rifle|.22]]-caliber sporting rifle styled after the SG 551. It uses a simple [[Blowback (arms)#Simple blowback|blowback]] semi-automatic operating system and its barrel has a 406&nbsp;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.<ref>{{Cite web|url=https://www.sanswissarms.com/news.html|title = Jdi Firearms, inc – Swiss Arms, Swat Training, Texas Concealed Carry}}</ref>

==Regulation==
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".<ref>{{cite web|url=http://www.cbc.ca/news/politics/gun-debate-reignites-with-rumoured-ban-of-classic-green-rifle-1.2554372|title=Gun debate reignites with rumored ban of Classic Green rifle|date=28 February 2014|access-date=25 December 2014|archive-url=https://web.archive.org/web/20150108180539/http://www.cbc.ca/news/politics/gun-debate-reignites-with-rumoured-ban-of-classic-green-rifle-1.2554372|archive-date=8 January 2015|url-status=live}}</ref> The rifle had been popular  with hunters and gun enthusiasts, who until February 2014, only required a [[possession 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|date=June 2022}} 

The [[National Firearms Association]] of Canada considered pursuit of the matter through the legal system.<ref>{{cite web|url=http://vancouver.24hrs.ca/2014/03/18/mounties-trample-canadian-gun-owners|title=Mounties trample Canadian gun owners|work=Vancouver 24 hrs|access-date=25 December 2014|archive-url=https://web.archive.org/web/20141225181426/http://vancouver.24hrs.ca/2014/03/18/mounties-trample-canadian-gun-owners|archive-date=25 December 2014|url-status=live}}</ref> On 31 July 2015, the Canadian government overturned the reclassification and returned the Swiss rifles to the original classifications.<ref>{{cite web|url=http://news.gc.ca/web/article-en.do?nid=1014559|title=Harper Government amends firearms classifications regulations|work=news.gc.ca|access-date=1 August 2015|archive-url=https://web.archive.org/web/20150807182324/http://news.gc.ca/web/article-en.do?nid=1014559|archive-date=7 August 2015|url-status=live}}</ref> 

On 1 May 2020, in the wake of the [[2020 Nova Scotia attacks|Nova Scotia attacks]], the rifles were again reclassified as Prohibited Firearms via [[Order in Council]].<ref>{{cite web|url=http://gazette.gc.ca/rp-pr/p2/2020/2020-05-01-x3/html/sor-dors96-eng.html|title=Regulations Amending the Regulations Prescribing Certain Firearms and Other Weapons, Components and Parts of Weapons, Accessories, Cartridge Magazines, Ammunition and Projectiles as Prohibited, Restricted or Non-Restricted|date=May 2020|access-date=22 October 2020}}</ref>

==Gallery==
<gallery>
Image:Caroline-profile-bipode-p1000509.jpg|With bipod extended.
Image:Fass90-bayonette-p1000786.jpg|With [[bayonet]].
Image:Caroline-crosse-repliee-p1000515.jpg|Stock folded.
Image:Caroline-canon-degivrage-p1000523.jpg|Flash suppressor and gas regulator.
Image:SIG 550 IMG 3276.jpg|The gas block integrates an adjustable gas regulator, the front sight with a flip-up night sight post, and the bayonet lug on the flash suppressor.
Image:SIG-552-p1030040.jpg|The SG 552 Commando version with integral [[Picatinny rail]] and accessories.

</gallery>

==Users==
[[File:SIG SG 550 Users.png|thumb|Map with SIG SG 550 users in blue]]<!--READ FIRST: This section is for cited entries only. Please do not add entries into this list without a citation from a reliable source. All entries without a citation will be removed. Thank you.-->

{| class="wikitable"
|-
! width="90px"| Country/Territory
! Organization
! Model
! Quantity
! Date
! Reference
|-
|{{ARG}}
|[[Grupo Especial de Operaciones Federales (Argentina)|GEOF, Federal Police]]
''Grupo de Especial de Seguridad, Policia de Mendoza''
|align="center"| SG 553 SOW SG 556
|align="center"| _
|align="center"| _
|align="center"| <ref name="Swiss Arms (Sig) SG 553 SOW Commando October 9, 2011">{{cite web |url=http://www.gunsite.co.za/content/articles/swiss-arms-sig-sg-553-sow-commando/ |title=Swiss Arms (Sig) SG 553 SOW Commando |date=13 December 2007 |publisher=GunSite South Africa |access-date=25 March 2012 |archive-url=https://web.archive.org/web/20120424153247/http://www.gunsite.co.za/content/articles/swiss-arms-sig-sg-553-sow-commando/ |archive-date=24 April 2012 |url-status=live }}</ref>
<ref>{{Cite web|url=https://fuerzasaeronavales.com/|archive-url=https://web.archive.org/web/20150924015947/http://www.fuerzasaeronavales.com/wp-content/uploads/www.fuerzasaeronavales.com_.002061.jpg|url-status=dead|title=fuerzasaeronavales|archive-date=24 September 2015}}</ref>
|-
|{{BRA}}
|[[Federal Police Department|Brazilian Federal Police]], [[Brazilian Air Force]] PARA-SAR
|align="center"| SG 550<br />SG 551
|align="center"| _
|align="center"| _
|align="center"| <ref name="jones2009">Jones, Richard D. ''Jane's Infantry Weapons 2009/2010''. Jane's Information Group; 35th ed., (2009). {{ISBN|978-0-7106-2869-5}}.</ref>
|-
|rowspan="2"|{{CAN}}
|[[Lethbridge Police Service]]
|rowspan="2" align="center"| SIG 553
|align="center"| _
|align="center"| _
|rowspan="2" align="center"| {{citation needed|date=January 2013}}
|-
|[[CN Police]]
|align="center"| _
|align="center"| _
|-
|rowspan="1"|{{EGY}}
|[[Sa'ka Forces]] and [[Unit 777]]
|align="center"| SG 552
|align="center"| _
|align="center"| _
|align="center"|  {{citation needed|date=May 2022}}
|-
|rowspan="1"|{{FIN}}
|Helsinki Police Department, [[Karhu Team]]
|align="center"| SG 552
|align="center"| _
|align="center"| _
|align="center"| <ref>Suomen sotilas 3/2006</ref>
|-
|rowspan="2"|{{FRA}}
|[[Special Operations Command (France)|Special Operations Command]] of the [[French Army]]
|align="center"| SG 551<br />SG 551 LB
|align="center"| _
|align="center"| _
|align="center"| <ref>{{cite web|url=http://www.defense.gouv.fr/terre/decouverte/materiels/materiels_specifiques/sig_551 |title=Terre – SIG 551 |language=fr |publisher=Defense.gouv.fr |date= 5 June 2013|archive-url=https://web.archive.org/web/20160920000829/https://www.defense.gouv.fr/terre/equipements/materiels-forces-speciales/sig-551|archive-date=20 September 2016}}</ref>
|-
|[[National Gendarmerie Intervention Group]] (GIGN) of the [[National Gendarmerie]]
|align="center"| SG 553 SOW
|align="center"| _
|align="center"| _
|align="center"| <ref name="Swiss Arms (Sig) SG 553 SOW Commando October 9, 2011"/>
|-
|rowspan="2"|{{GER}}
|[[GSG 9]] of the [[German Federal Police]]
|rowspan="2" align="center"| SIG 553 SOW
|align="center"| _
|align="center"| _
|rowspan="2" align="center"| <ref name="Swiss Arms (Sig) SG 553 SOW Commando October 9, 2011"/><ref>{{Cite web| url=http://www.swatseries.com/Images/C_7-8_06_Suenkler.pdf | title=Die heimlichen Helden vom Rhein | language=de | trans-title=The Secret Heroes of the Rhine | access-date=6 October 2012 | url-status=dead | archive-url=https://web.archive.org/web/20110716171700/http://www.swatseries.com/Images/C_7-8_06_Suenkler.pdf | archive-date=16 July 2011}}</ref>
|-
|''[[Spezialeinsatzkommando]]'' (Special Task Force) groups of some ''[[Landespolizei]]'' (State Police)
|align="center"| _
|align="center"| _
|-
|{{IND}}
|[[National Security Guard]]
|align="center"| SG 551
|align="center"| 675
|align="center"|  ~2010
|align="center"| <ref>{{cite web|url=http://www.indianexpress.com/news/post-26-11-nsg-aims-for-corner-shot-weapons-throughthewall-radars/537983|title=Post 26/11, NSG aims for corner shot weapons, through-the-wall radars|access-date=25 December 2014|archive-url=https://web.archive.org/web/20091111105300/http://www.indianexpress.com/news/post-26-11-nsg-aims-for-corner-shot-weapons-throughthewall-radars/537983|archive-date=11 November 2009|url-status=live}}</ref><ref>{{cite journal|title=Small Arms of the Indian State: A Century of Procurement and Production|first1=Aaron|last1=Karp|first2=Rajesh|last2=Rajagopalan|publisher=Small Arms Survey|date=January 2014|url=https://www.files.ethz.ch/isn/176291/IAVA-IB4-small-arms-of-indian-state.pdf|jstor=resrep10661|journal=Issue Brief|issue=4|pages=5–7|access-date=2 January 2019|archive-url=https://web.archive.org/web/20190102193406/https://www.files.ethz.ch/isn/176291/IAVA-IB4-small-arms-of-indian-state.pdf|archive-date=2 January 2019|url-status=live}}</ref>
|-
| rowspan="3" |{{IDN}}
| ''[[Kopassus|Komando Pasukan Khusus]]'' (Kopassus) special forces group of the [[Indonesian Army]]
|rowspan="2" align="center"|SG 550<br />SG 552
|align="center"| _
|align="center"| _
|rowspan="2" align="center"|<ref name="idnvojnik">{{cite web |url=http://www.hrvatski-vojnik.hr/hrvatski-vojnik/1612007/ind.asp |title=Kopassus & Kopaska – Specijalne Postrojbe Republike Indonezije |language=hr |publisher=Hrvatski Vojnik Magazine |access-date=12 June 2010 |url-status=dead |archive-url=https://web.archive.org/web/20100822145526/http://www.hrvatski-vojnik.hr/hrvatski-vojnik/1612007/ind.asp |archive-date=22 August 2010  }}</ref>
|-
|''[[Kopaska|Komando Pasukan Katak]]'' (Kopaska) tactical diver group of the [[Indonesian Navy]]
|align="center"| _
|align="center"| _
|-
| [[Indonesian Marine Corps]]
| align="center" |SG 550-1
| align="center" |_
| align="center" |_
| align="center" |<ref>{{Cite web |last=indomiliter |date=2015-07-13 |title=SIG 550 Sniper: Senapan Runduk Andalan Korps Marinir di Kaliber 5,56 mm |url=https://www.indomiliter.com/sig-550-sniper-senapan-runduk-andalan-korps-marinir-di-kaliber-556-mm/ |access-date=2025-06-05 |website=Indomiliter.com |language=Indonesian}}</ref><ref>{{Cite web |last=Dispen Kormar |date=2021-05-18 |title=Berlatih Menembak, Cara Regu Pandu Tempur Yonif 5 Marinir Asah Naluri Tempur |url=https://www.mediapadjajaran.com/2021/05/berlatih-menembak-cara-regu-pandu.html |access-date=2025-06-05 |website=mediapadjajaran.com |language=Indonesian}}</ref>
|-
|rowspan="4"|{{flag|Malaysia}}
|''[[Grup Gerak Khas]]'' (GGK) Counter-Terrorism Forces of the [[Malaysian Army]]
|rowspan="4" align="center"| SG 553 LB<br />SG 553 SB
|align="center"| _
|align="center"| _
|align="center"|  {{citation needed|date=June 2023}}
|-
|[[JMF Elite Forces]] Counter-Terrorism Forces of the [[Royal Johor Military Force]]
|align="center"| _
|align="center"| _
|align="center"|  {{citation needed|date=June 2023}}
|-
|''[[PASKAU|Pasukan Khas Udara]]'' (PASKAU) Counter-Terrorism Forces of the [[Royal Malaysian Air Force]]
|align="center"| _
|align="center"| _
|align="center"|<ref>{{cite web |url=http://www.tactical-life.com/online/special-weapons/malaysian-special-forces |title=Malaysian Special Forces |author=Thompson, Leroy |date=December 2008 |publisher=Special Weapons |access-date=28 November 2009 |archive-url=https://web.archive.org/web/20120402013858/http://www.tactical-life.com/online/special-weapons/malaysian-special-forces/ |archive-date=2 April 2012 |url-status=live }}</ref><ref>{{cite web|url=http://www.utusan.com.my/utusan/info.asp?y=2008&dt=1210&pub=utusan_malaysia&sec=Polis_%26_Tentera&pg=te_01.htm&arc=hive|title=Sig SG 553 is a new rifle for PASKAU|date=10 December 2008|access-date=28 November 2009|work=[[Utusan Malaysia]]|author=Zabry Mohamad Madzlan|archive-url=https://web.archive.org/web/20090603211834/http://www.utusan.com.my/utusan/info.asp?y=2008&dt=1210&pub=utusan_malaysia&sec=Polis_%26_Tentera&pg=te_01.htm&arc=hive|archive-date=3 June 2009|url-status=dead}}</ref>
|-
|[[Special Task and Rescue]] (STAR) Maritime Counter-Terrorism Forces of the [[Malaysian Maritime Enforcement Agency]]
|align="center"| _
|align="center"| _
|align="center"|<ref>{{cite web|url=http://malaysiadefender.blogspot.com/2012/04/dsa2012-ssg-553-pilihan-pasukan-elit.html|title=DSA2012 – SIG SG 553 Pilihan Pasukan Elit|author=MalaysiaDefender|language=ms|access-date=17 January 2012|archive-url=https://web.archive.org/web/20130801045610/http://malaysiadefender.blogspot.com/2012/04/dsa2012-ssg-553-pilihan-pasukan-elit.html|archive-date=1 August 2013|url-status=live}}</ref>
|-
|{{flagu|Malta}}
|''[[Armed Forces of Malta]]''
|align="center"| SG 550
|align="center"| _
|align="center"| _
|align="center"| <ref name="SIG SG 550 (Sturmgewehr Model 550) / Stgw 90 Assault Rifle / Carbine June 22, 2014"/>
|-
|{{PAK}}
|[[Special Service Group]] Counter-Terrorism Forces of the [[Pakistan Army]]
|align="center"| _
|align="center"| _
|align="center"| _
|align="center"| <ref>{{cite web|url=http://www.militaryfactory.com/smallarms/pakistan-special-service-group-weapons.asp|title=Pakistan Special Service Group|author=Dan Alex|access-date=8 June 2016|archive-url=https://web.archive.org/web/20160613141325/http://www.militaryfactory.com/smallarms/pakistan-special-service-group-weapons.asp|archive-date=13 June 2016|url-status=live}}{{better source needed|date=January 2019}}</ref>
|-
|-
|{{PNG}}
|[[Royal Papua New Guinea Constabulary]] 
| style="text-align:center;"| _
| style="text-align:center;"| _
| style="text-align:center;"| _
|
|-
|{{POL}}
|''[[GROM]]'' special forces of the [[Polish Armed Forces]]
|align="center"| SG-551P SWAT
|align="center"| _
|align="center"| _
|align="center"| <ref name="Swiss Arms (Sig) SG 553 SOW Commando October 9, 2011"/><ref>{{cite news|first=Remigiusz|last=Wilk (REMOV)|url=http://www.altair.com.pl/cz-art-1660|title=Nowe gromy GROM|url-status=dead|archive-url=https://web.archive.org/web/20100326120026/http://www.altair.com.pl/cz-art-1660|archive-date=26 March 2010}}</ref><ref>{{cite web|url=http://grom.mil.pl/uzbrojenie_pliki/UZBROJENIE.HTM|title=GROM Utility and Equipment|access-date=2 August 2009|url-status=dead|archive-url=https://web.archive.org/web/20120208072009/http://www.grom.mil.pl/uzbrojenie_pliki/UZBROJENIE.HTM|archive-date=8 February 2012}}</ref>
|-
| rowspan="3" |{{ROM}}
|''[[Detașamentul de Căutare-Salvare prin Luptă]]'' (DCSL; Combat Search and Rescue) special forces of the [[Romanian Air Force]]
| rowspan="3" align="center" | SG 551<br />SG 552<br />SG 553
| rowspan="3" align="center" | _
| rowspan="3" align="center" | _
| rowspan="3" align="center"| <ref>{{Cite web |url=http://www.resboiu.ro/arhanghel-pe-borcea/ |title=Arhangheli pe Borcea |date=8 October 2016 |access-date=16 October 2016 |archive-url=https://web.archive.org/web/20161014152601/http://www.resboiu.ro/arhanghel-pe-borcea/ |archive-date=14 October 2016 |url-status=live }}</ref><ref name="special forces">{{cite web|url=http://romanianspecialforces.com/vulturii.html|title=Special Forces|work=romanianspecialforces.com|url-status=usurped|archive-url=https://web.archive.org/web/20131126221021/http://romanianspecialforces.com/vulturii.html|archive-date=2013-11-26}}</ref><ref name="fotob1">{{cite web|url=https://www.brigadaspeciala.ro/fotob1dotare.html|title=FotoB1dotare|website=brigadaspeciala.ro|access-date=28 May 2023|archive-date=16 August 2023|archive-url=https://ghostarchive.org/archive/20230816200853/https://www.brigadaspeciala.ro/fotob1dotare.html|url-status=dead}}</ref>
|-
|[[Romanian Naval Forces]] 307th Marine Infantry Regiment – reconnaissance units
|-
|''[[Brigada Specială de Intervenție a Jandarmeriei]]'' (BSIJ)
|-
|{{KSA}}
|[[Royal Saudi Navy]] Special Forces Units
|align="center"| SG 556 SWAT<br />SG 552<br />SG 556 SBR
|align="center"| _
|align="center"| _
|align="center"| <ref>{{Cite web| title=Soldier with a machine gun | url=https://i.imgur.com/beTshQN.jpg | archive-url=https://web.archive.org/web/20230412181407/https://i.imgur.com/beTshQN.jpg | archive-date=2023-04-12}}</ref><ref>{{Cite web| title=Sheikh with a gun | url=https://i.imgur.com/AGObXCc.jpg | archive-url=https://web.archive.org/web/20230412105714/https://i.imgur.com/AGObXCc.jpg | archive-date=2023-04-12}}</ref><ref>{{Cite web| title=Soldier with a machine gun | url=https://i.imgur.com/27xpuHL.jpg | archive-url=https://web.archive.org/web/20230412154132/https://i.imgur.com/27xpuHL.jpg | archive-date=2023-04-12}}</ref>
|-
|{{SRB}}
|''[[Special Anti-Terrorist Unit (Serbia)|Specijalna Antiteroristicka Jedinica]]'' (Special Anti-terrorist Unit) of the [[Police of the Republic of Serbia|Serbian Police]]
|align="center"| SIG SG 552
|align="center"| _
|align="center"| _
|align="center"| <ref>{{cite web |url=http://www.rtbot.net/saj._jedinica |title=SAJ-Specialna Anti-teroristička Jedinica |publisher=rtbot.net |archive-url=https://web.archive.org/web/20150924092519/http://www.rtbot.net/saj._jedinica |archive-date=24 September 2015 |url-status=live }}</ref>
|-
|{{SVK}}
|''Útvar Osobitného Určenia'' (Special Assignments Unit) of the [[Slovak Police]]
|align="center"| SG 551 SWAT
|align="center"| _
|align="center"| _
|align="center"| <ref>{{cite web |url=http://www.specialunits.sk/uou_svk.htm |title=Špeciálne jednotky Slovenskej republiky |publisher=Specialunits.sk |access-date=9 July 2009 |archive-url=https://web.archive.org/web/20090715090813/http://www.specialunits.sk/uou_svk.htm |archive-date=15 July 2009 |url-status=dead  }}</ref>
|-
|{{ROK}}
|''Special Sea Attack Team (SSAT)'' of the [[Korea Coast Guard]]
|align="center"| SG 556
|align="center"| _
|align="center"| _
|align="center"| <ref name="Adrenaline:Burn Out [Part1] January 11, 2013">{{cite web |url=https://www.youtube.com/watch?v=kIhV8ANrd8I |title=Adrenaline: Burn Out [Part1] |date=11 January 2013 |publisher=INSITE TV |access-date=10 October 2013 |archive-url=https://web.archive.org/web/20160527174238/https://www.youtube.com/watch?v=kIhV8ANrd8I |archive-date=27 May 2016 |url-status=live }}</ref>
|-
|{{ESP}}
|[[Grupo Especial de Operaciones]] of the [[Spanish National Police]]
|align="center"| SG 551 SWAT<br />SG 552
|align="center"| _
|align="center"| _
|align="center"| <ref>{{cite web |url=http://www.policia.es/geo/material.htm?reload_coolmenus |title=Web Del Grupo Especial De Operaciones (G.E.O.) |publisher=Policia.es |access-date=9 July 2009 |url-status=dead |archive-url=https://web.archive.org/web/20090606025613/http://www.policia.es/geo/material.htm?reload_coolmenus |archive-date=6 June 2009  }}</ref><ref>{{cite web |url=http://www.policia.es/geo/fusiles_asalto.htm?reload_coolmenus |title=Web Del Grupo Especial De Operaciones (G.E.O.) |publisher=Policia.es |access-date=9 July 2009 |url-status=dead |archive-url=https://web.archive.org/web/20081213203751/http://www.policia.es/geo/fusiles_asalto.htm?reload_coolmenus |archive-date=13 December 2008  }}</ref>
|-
|{{flagcountry|Switzerland}}
|[[Swiss Armed Forces]]
|align="center"| SG 550 <br />SG 552 <br />SG 553
|align="center"| 450,000<ref name ='SAS 2002'>{{cite book|url=http://www.smallarmssurvey.org/publications/by-type/yearbook/small-arms-survey-2002.html|chapter-url=http://www.smallarmssurvey.org/fileadmin/docs/A-Yearbook/2002/en/Small-Arms-Survey-2002-Chapter-02-EN.pdf|chapter=Red Flags and Buicks: Global Firearms Stockpiles|title=Small Arms Survey 2002: Counting the Human Cost|publisher=[[Oxford University Press]]|year=2015|author=Small Arms Survey|author-link=Small Arms Survey|ref={{harvid|Small Arms Survey 2002}}|page=78|access-date=29 August 2018|archive-url=https://web.archive.org/web/20180829175556/http://www.smallarmssurvey.org/publications/by-type/yearbook/small-arms-survey-2002.html|archive-date=29 August 2018|url-status=dead}}</ref>
|align="center"| _
|align="center"| <ref>{{cite web|url=http://www.lba.admin.ch/internet/lba/de/home/themen/ausrue/pers0/bewaffnung/stgw90.html |title=Sturmgewehr 90 (Stgw 90) |publisher=Lba.admin.ch |date=20 November 2008 |access-date=9 July 2009 |url-status=dead |archive-url=https://web.archive.org/web/20090203065917/http://www.lba.admin.ch/internet/lba/de/home/themen/ausrue/pers0/bewaffnung/stgw90.html |archive-date=3 February 2009 }}</ref>
|-
|{{TWN}}
|Wei-An Police Special Services Commando
|align="center"| SG 551-1P
|align="center"| _
|align="center"| 1994
|align="center"| <ref>http://www.wargamehk.com/SG551.htm {{Webarchive|url=https://web.archive.org/web/20170929031729/http://wargamehk.com/SG551.htm |date=29 September 2017 }} / 台灣的維安特勤隊是世界上少數使用 SG550-1P 的反恐怖特警隊(Traditional Chinese)</ref>
|-
|{{TUR}}
|''[[Police Counter Attack Team|Karşı Atak Timi]]'' (Counter Attack Team), police special forces of the [[General Directorate of Security (Turkey)|General Directorate of Security]]
|align="center"| SG 553
|align="center"| _
|align="center"| _
|align="center"|<ref>http://www.haberturk.com/gundem/haber/662480-cat-timine-100-yeni-tabanca {{Webarchive|url=https://web.archive.org/web/20120116091108/http://www.haberturk.com/gundem/haber/662480-cat-timine-100-yeni-tabanca |date=16 January 2012 }} (Turkish)</ref>
|-
|{{TUN}}
|''Groupe d'Intervention Présidentielle'' (GIP) special forces of the Presidential Guard
|align="center"| SG 552
|align="center"| _
|align="center"| _
|align="center"| <ref>https://fbcdn-sphotos-c-a.akamaihd.net/hphotos-ak-prn1/t1/1560770_658196010886458_2135580448_n.jpg {{Webarchive|url=https://web.archive.org/web/20140222195322/https://fbcdn-sphotos-c-a.akamaihd.net/hphotos-ak-prn1/t1/1560770_658196010886458_2135580448_n.jpg |date=22 February 2014 }} (GIP Operator with SIG 552)</ref>
|-
| rowspan="4"|{{GBR}}
| [[West Mercia Police]]
| style="text-align:center;"| SG 551 SWAT
| style="text-align:center;"| _
| style="text-align:center;"| _
| style="text-align:center;"|
|-
| [[Derbyshire Police]] (previously used)
| style="text-align:center;"| SG 552
| style="text-align:center;"| _
| style="text-align:center;"| _
| style="text-align:center;"|<ref>{{cite web |url=http://www.eliteukforces.info/police/uk-armed-police |title=British Armed Response Unit |publisher=Elite UK Forces |access-date=23 January 2016 |archive-url=https://web.archive.org/web/20160209220731/http://www.eliteukforces.info/police/uk-armed-police/ |archive-date=9 February 2016 |url-status=live }}</ref>
|-
| [[West Yorkshire Police]]
| rowspan="2" style="text-align:center;"| SG 553
| style="text-align:center;"| _
| style="text-align:center;"| _
| rowspan="2" style="text-align:center;"|<ref>{{cite web |url=http://www.yorkshirearmycadets.co.uk/cadets/ecoy/ereport3.htm |title=Cadets Cause a Riot |website=www.yorkshirearmycadets.co.uk |archive-url=https://web.archive.org/web/20140201194128/http://www.yorkshirearmycadets.co.uk/cadets/ecoy/ereport3.htm |archive-date=1 February 2014}}</ref>
|-
| [[Staffordshire Police]]
| style="text-align:center;"| _
| style="text-align:center;"| _
|-
|rowspan="3"|{{USA}}
|[[Drug Enforcement Administration]]
|align="center"| SG 551<br />SG 553 SOW
|align="center"| _
|align="center"| _
|align="center"|<ref name="Swiss Arms (Sig) SG 553 SOW Commando October 9, 2011"/><ref name="Exeter's Sigarms gets $115 million federal rifle contract 2003-07-11">{{cite web |url=http://premium1.fosters.com/2003/news/jul_03/july_11/news/bu_0711k.asp |title=Exeter's Sigarms gets $115 million federal rifle contract |publisher=Premium1.fosters.com |date=11 July 2003 |access-date=17 November 2009 |url-status=dead |archive-url=https://web.archive.org/web/20110711021332/http://premium1.fosters.com/2003/news/jul_03/july_11/news/bu_0711k.asp |archive-date=11 July 2011  }}</ref>
|-
|[[Federal Bureau of Investigation]]
|align="center"| SG 551
|align="center"| _
|align="center"| _
|align="center"| <ref name="Exeter's Sigarms gets $115 million federal rifle contract 2003-07-11"/>
|-
|[[SWAT|Special Weapons And Tactics]] (SWAT) counter-terrorism forces of the [[United States Capitol Police]]
|align="center"| SG 550
|align="center"| _
|align="center"| _
|align="center"| <ref>{{cite web |url=http://www.militaryfactory.com/smallarms/swat-team-weapons.asp |title=SWAT Weapons |publisher=Military Factory |date=30 December 2015 |access-date=1 February 2016 |archive-url=https://web.archive.org/web/20160125125415/http://www.militaryfactory.com/smallarms/swat-team-weapons.asp |archive-date=25 January 2016 |url-status=live }}{{better source needed|date=January 2019}}</ref>
|-
|{{flagu|Vatican City}}
||[[Swiss Guard#Pontifical Swiss Guard|Pontifical Swiss Guard]]
|align="center"| SG 550<br />SG 552
|align="center"| _
|align="center"| _
|align="center"| <ref>{{cite web|url=https://www.guns.com/news/2017/04/16/guns-swiss-guard/ |work=guns.com |archive-url=https://web.archive.org/web/20140729061922/http://www.guns.com/2014/04/13/guns-swiss-guard/ |archive-date=29 July 2014 |title= Guns of the Swiss Guard}}</ref>
|-
|{{VEN}}
||[[Venezuelan Marine Corps]]
|align="center"| SG 550<br />SG 552
|align="center"| _
|align="center"| _
|align="center"| <ref>{{cite news | url=https://www.wsj.com/articles/the-guns-of-venezuela-1502053005 | title=The Guns of Venezuela | newspaper=The Wall Street Journal | first=Mary Anastasia | last=O’Grady | date=6 August 2017 | access-date=31 March 2018 | archive-url=https://web.archive.org/web/20180306161008/https://www.wsj.com/articles/the-guns-of-venezuela-1502053005 | archive-date=6 March 2018 | url-status=live }}</ref>
|}

==See also==
*[[SIG SG 530]]
*[[SIG SG 540]]
*[[SIG Sauer SIG516]]
*[[Gun politics in Switzerland]]
*[[List of assault rifles]]
*[[List of carbines]]
*[[List of sniper rifles]]
==Notes==
{{notelist}}
==References==
{{Reflist|30em}}

==Bibliography==
*''Règlement 53.96 Fusil d'assaut 5.6&nbsp;mm 1990''{{incomplete citation|date=September 2023}}

==External links==
{{Commons and category|SIG SG 550}}
*[https://web.archive.org/web/20090422004200/http://www.peelclub.com/downloads/manuals/flyer_pe90_e.pdf Swiss Arms PE 90 brochure]
*[http://world.guns.ru/assault/switch/sig-550--551--552-e.html Modern Firearms]
*[http://www.biggerhammer.net/sigamt/ Biggerhammer.net – portal for articles, information and manuals, etc. on the SIG Stgw 57/SG 510/AMT and SG 550 rifle series]
*[http://www.biggerhammer.net/sigamt/550/550techinspection/ SG 550/551 technical data and test documentation]
*[http://www.swissrifles.com/sig550/ The SIG SG 550 series – information, manuals and links]
*[https://web.archive.org/web/20110705041016/http://sigsauer.com/upFiles/CmsContent/documents/OwnerManual/SG550551OM.pdf SG 550/551 instruction manual]
*[https://web.archive.org/web/20080414141931/http://swissarms2.ath.cx/fileadmin/editor/downloads/manuals/SG552_manual_GB.pdf SG 552 instruction manual]
*[http://www.rettung-bs.ch/fileadmin/militaer/schiessplatz_kurse/stgw90/stgw90.pdf Swiss Armed Forces Stgw 90 manual {{in lang|de}}] {{Webarchive|url=https://web.archive.org/web/20101010195557/http://www.rettung-bs.ch/fileadmin/militaer/schiessplatz_kurse/stgw90/stgw90.pdf |date=10 October 2010 }}
*[https://www.wsj.com/articles/the-guns-of-venezuela-1502053005 The Guns of Venezuela]

{{Swiss Arms}}
{{Current French infantry weapons}}
{{Kalashnikov rifle}}

[[Category:Carbines]]
[[Category:Weapons and ammunition introduced in 1986]]
[[Category:5.56 mm assault rifles]]
[[Category:5.56×45mm NATO assault rifles]]
[[Category:.300 BLK firearms]]
[[Category:7.62×39mm assault rifles]]
[[Category:7.62×51mm NATO battle rifles]]
[[Category:Assault rifles of Switzerland]]
[[Category:SIG Sauer rifles]]
[[Category:Sniper rifles of Switzerland]]
[[Category:Long stroke piston firearms]]