The SG 550 is an

assault rifle An assault rifle is a select fire rifle that uses an intermediate cartridge, intermediate-rifle cartridge and a Magazine (firearms), detachable magazine.C. Taylor, ''The Fighting Rifle: A Complete Study of the Rifle in Combat'', F.A. Moyer '' ...

manufactured by SIG Sauer AG (formerly a division of

Schweizerische Industrie Gesellschaft SIG Group AG is a Swiss multinational corporation and one of the biggest manufacturers in the packaging industry. Originally founded 1853 as a railway car producer named ''Schweizerische Waggonfabrik'' ("Swiss Wagon Factory"), it was renamed ...

, 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 The 5.56×45mm NATO (official NATO nomenclature 5.56 NATO, commonly pronounced "five-five-six") is a rimless bottlenecked centerfire intermediate cartridge family developed in the late 1970s in Belgium by FN Herstal. It consists of the SS109, ...

SIG SG 540 The SG 540 is a 5.56×45mm NATO assault rifle developed in the early 1970s by Schweizerische Industrie Gesellschaft (SIG, currently SAN Swiss Arms AG) of Neuhausen am Rheinfall, Neuhausen, Switzerland as a private venture primarily destined for ...

History

Development

In 1978, the

Swiss armed forces The Swiss Armed Forces (; ; ; ; ) are the military and security force of Switzerland, consisting of land and air service branches. Under the country's militia system, regular soldiers constitute a small part of the military and the rest are ...

formulated requirements for a successor to the

Stgw 57 The Sturmgewehr 57 (Stgw. 57 ) is a selective fire battle rifle designed by Schweizerische Industrie Gesellschaft (now Swiss Arms, SAN Swiss Arms) of Switzerland. The Stgw. 57 assault rifle uses a Blowback (arms)#Roller-delayed, roller-delayed bl ...

battle rifle A battle rifle is a service rifle chambered to fire a fully powered cartridge. The term "battle rifle" is a retronym created largely out of a need to differentiate automatic rifles chambered for fully powered cartridges from automatic rifles cha ...

(known commercially as the SG 510) using the 7.5×55mm GP 11 cartridge. Emphasis was placed on

modularity Modularity is the degree to which a system's components may be separated and recombined, often with the benefit of flexibility and variety in use. The concept of modularity is used primarily to reduce complexity by breaking a system into varying ...

; the weapon family was to include several variants of the base design, including a compact

carbine A carbine ( or ) is a long gun that has a barrel shortened from its original length. Most modern carbines are rifles that are compact versions of a longer rifle or are rifles chambered for less powerful cartridges. The smaller size and ligh ...

that would be issued to rear-echelon and support troops, command staff, vehicle crews,

special forces Special forces or special operations forces (SOF) are military units trained to conduct special operations. NATO has defined special operations as "military activities conducted by specially designated, organized, selected, trained and equip ...

personnel and

paratrooper A paratrooper or military parachutist is a soldier trained to conduct military operations by parachuting directly into an area of operations, usually as part of a large airborne forces unit. Traditionally paratroopers fight only as light infa ...

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 W, or w, is the twenty-third letter of the Latin alphabet, used in the modern English alphabet, the alphabets of other western European languages and others worldwide. Its name in English is ''double-u'',Pronounced in formal situation ...

(developed by the state-owned

Waffenfabrik Bern Weapons Factory Bern (, also known as W+F Bern), was an arms manufacturer in Bern, Switzerland, which was a government-owned corporation producing firearms for the Swiss Armed Forces. W+F was integrated into RUAG in 1999, which later discontin ...

, using both 6.45×48mm and 5.56×45mm cartridges) and the SG 541 (developed by SIG using the SG 540 as the basis for the SG 541 prototype). In 1981, the experimental 6.45mm GP 80 cartridge was rejected in favor of the more conventional SIG 5.6×45mm Gw Pat 90 round (with a 4.1 g,

tombac Tombac, or tombak, is a brass alloy with high copper content and 5–20% zinc content. Tin, lead or arsenic may be added for colouration. It is a cheap malleable alloy mainly used for medals, ornament, decoration and some munitions. In older ...

-jacketed,

lead Lead () is a chemical element; it has Chemical symbol, symbol Pb (from Latin ) and atomic number 82. It is a Heavy metal (elements), heavy metal that is density, denser than most common materials. Lead is Mohs scale, soft and Ductility, malleabl ...

core projectile) that is the Swiss equivalent to

NATO The North Atlantic Treaty Organization (NATO ; , OTAN), also called the North Atlantic Alliance, is an intergovernmental organization, intergovernmental Transnationalism, transnational military alliance of 32 Member states of NATO, member s ...

's standard 5.56×45mm cartridge. C42 6

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.

Design details

Operating mechanism

The SG 550 is a selective-fire 5.56×45mm NATO

firing from a

closed bolt A semi or full-automatic firearm which is said to fire from a closed bolt or closed breech is one where, when ready to fire, a round is in the chamber and the bolt and working parts are forward ''in battery''. When the trigger is pulled, the ...

. It has a

gas-actuated Gas-operation is a system of operation used to provide energy to operate locked breech, autoloading firearms. In gas-operation, a portion of high-pressure gas from the cartridge being fired is used to power a mechanism to dispose of the spent ...

piston-driven long-stroke operating system derived from the

series of rifles, which uses burnt powder gases vented through a port in the

barrel A barrel or cask is a hollow cylindrical container with a bulging center, longer than it is wide. They are traditionally made of wooden stave (wood), staves and bound by wooden or metal hoops. The word vat is often used for large containers ...

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 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 is incorporated into the bolt while a fixed protrusion on one of the receiver's internal guide rails ejects the spent cartridge casings.

Features

The rifle is hammer-fired and has a trigger mechanism with an

ambidextrous Ambidexterity is the ability to use both the right and left hand equally well. When referring to objects, the term indicates that the object is equally suitable for right-handed and left-handed people. When referring to humans, it indicates that ...

safety Safety is the state of being protected from harm or other danger. Safety can also refer to the control of recognized hazards in order to achieve an acceptable level of risk. Meanings The word 'safety' entered the English language in the 1 ...

and fire selector switch that has 4 settings: "S"—safe, "1"—single fire, "3"—3-round

burst Burst may refer to: *Burst mode (disambiguation), a mode of operation where events occur in rapid succession **Burst transmission, a term in telecommunications **Burst switching, a feature of some packet-switched networks **Bursting, a signaling mo ...

and "20"—fully

automatic fire An automatic firearm or fully automatic firearm (to avoid confusion with semi-automatic firearms) is a self-loading firearm that continuously chambers and fires rounds when the trigger mechanism is actuated. The action of an automatic firearm i ...

. 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 Trigger may refer to: Arts, entertainment and media Fictional entities * Trigger (''Only Fools and Horses''), in the TV sitcom * Trigger Argee, in science fiction short stories by James H. Schmitz * Devil Trigger, a transformation ability of ...

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 . The firearm is fed by lightweight 20-round box magazines, 30-, 10- and 5-round magazines are also available. The magazines are

molded Molding (American English) or moulding (British and Commonwealth English; see spelling differences) is the process of manufacturing by shaping liquid or pliable raw material using a rigid frame called a mold or matrix. This itself may have ...

from a translucent polymer and can be locked together using studs in order to facilitate quicker reloading (

Jungle style In regards to firearm magazines, jungle style, or jungle magazines, or coupled magazines, refers to detachable box magazines, and thereof, that are fixed together side by side, for example, with tape, or purpose made ''magazine clamps'', also ...

). The empty weight of a 20-round magazine is and for a 30-round magazine. A bolt hold-open device locks the bolt carrier assembly open after expending the last cartridge from the

magazine A magazine is a periodical literature, periodical publication, print or digital, produced on a regular schedule, that contains any of a variety of subject-oriented textual and visual content (media), content forms. Magazines are generally fin ...

and is released by lifting the bolt catch lever located on the left side of the 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

buttstock A gunstock or often simply stock, the back portion of which is also known as a shoulder stock, a buttstock, or simply a butt, is a part of a long gun that provides structural support, to which the barrel, action, and firing mechanism are attac ...

(folds to the right side of the receiver) and a lightweight aluminium

bipod A bipod is a V-shaped portable attachment that helps support and steady a device, usually a weapon such as a long gun or a mortar. The term comes from the Latin prefix and Greek root , meaning "two" and "foot" respectively. Bipods are design ...

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 On a firearm or other tools, a pistol grip is a distinctly protruded handle underneath the main mechanism, to be held by the user's hand at a more vertical (and thus more ergonomic) angle, similar to how one would hold a conventional pistol. ...

, and handguards are made of a high-strength

polymer A polymer () is a chemical substance, substance or material that consists of very large molecules, or macromolecules, that are constituted by many repeat unit, repeating subunits derived from one or more species of monomers. Due to their br ...

, and are produced in either green or black colour options. The

steel Steel is an alloy of iron and carbon that demonstrates improved mechanical properties compared to the pure form of iron. Due to steel's high Young's modulus, elastic modulus, Yield (engineering), yield strength, Fracture, fracture strength a ...

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. The heavy, cold hammer-forged barrel is screwed into the receiver and is equipped with a slotted "bird cage" type

flash suppressor A flash suppressor, also known as a flash guard, flash eliminator, flash hider, or flash cone, is a device attached to the muzzle (firearms), muzzle of a rifle that reduces its Muzzle flash, visible signature while firing by cooling or dispersin ...

that is also used to launch

rifle grenade A rifle grenade is a grenade that uses a rifle-based launcher to permit a longer effective range than would be possible if the grenade were thrown by hand. The practice of projecting grenades with rifle-mounted launchers was first widely used dur ...

s (using standard, live

ammunition Ammunition, also known as ammo, is the material fired, scattered, dropped, or detonated from any weapon or weapon system. The term includes both expendable weapons (e.g., bombs, missiles, grenades, land mines), and the component parts of oth ...

) or attach a knife

bayonet A bayonet (from Old French , now spelt ) is a -4; we might wonder whether there's a point at which it's appropriate to talk of the beginnings of French, that is, when it wa ... , now spelt ) is a knife, dagger">knife">-4; we might wonder whethe ...

(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-oriented 5.56×45mm 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. All rifles are 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 R₅₀ or 50%

windage In aerodynamics, firearms ballistics, and automobiles, windage is the effects of some fluid, usually air (e.g., wind) and sometimes liquids, such as oil. Aerodynamics Windage is a force created on an object by friction when there is relative m ...

and

elevation The elevation of a geographic location (geography), ''location'' is its height above or below a fixed reference point, most commonly a reference geoid, a mathematical model of the Earth's sea level as an equipotential gravitational equipotenti ...

dispersion of any individual weapon must have been within an group at 300 m, the 50% windage and elevation dispersion must have averaged . The employed

circular error probable Circular error probable (CEP),Circular Error Probable (CEP), Air Force Operational Test and Evaluation Center Technical Paper 6, Ver 2, July 1987, p. 1 also circular error probability or circle of equal probability, is a measure of a weapon s ...

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 of

stainless steel Stainless steel, also known as inox, corrosion-resistant steel (CRES), or rustless steel, is an iron-based alloy that contains chromium, making it resistant to rust and corrosion. Stainless steel's resistance to corrosion comes from its chromi ...

. The barrel, bolt, bolt carrier, and firing pin are all made with steel that has been gas nitrided, hardened and tempered. The bolt and carrier, along with most other components internal to the receiver undergo a phosphating process.

Sights

The SG 550 series rifles have a long sight radius and are equipped with

iron sights Iron sights are a system of physical alignment markers used as a sighting device to assist the accurate aiming of ranged weapons such as firearms, airguns, crossbows, and bows, or less commonly as a primitive finder sight for optical telescop ...

adjustable for both windage and elevation. The sights are similar to those on some

Heckler & Koch Heckler & Koch GmbH (HK or H&K; ) is a German firearms manufacturer that produces handguns, rifles, submachine guns, and grenade launchers. The company is located in Oberndorf am Neckar, Baden-Württemberg and also has subsidiaries in the United ...

weapons, such as the

HK G3 The Heckler & Koch G3 () is a select-fire battle rifle chambered in 7.62×51mm NATO developed in the 1950s by the German firearms manufacturer Heckler & Koch, in collaboration with the Spanish state-owned firearms manufacturer CETME. The G3 ...

HK MP5 The Heckler & Koch MP5 (, ) is a submachine gun developed in the 1960s by German firearms manufacturer Heckler & Koch. It uses a similar modular design to the Heckler & Koch G3, and has over 100 variants and clones, including selective fire, s ...

. The sights consist of a rear, rotating

diopter A dioptre ( British spelling) or (American spelling), symbol dpt or D, is a unit of measurement with dimension of reciprocal length, equivalent to one reciprocal metre, . It is normally used to express the optical power of a lens or curved mi ...

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 0.15 mil (≈0.52

moa Moa are extinct giant flightless birds native to New Zealand. Moa or MOA may also refer to: Arts and media * Metal Open Air, a Brazilian heavy metal festival * MOA Museum of Art in Japan * The Moas, New Zealand film awards People * Moa ...

), or at 100 m. For night use, the dedicated "1" notch setting in the rear sight drum is provided with two self-luminous 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 An anti-tank grenade is a specialized hand-thrown grenade used to defeat armored targets. Although their inherently short range limits the usefulness of grenades, troops can lie in ambush or maneuver under cover to exploit the limited outward vis ...

s. For designated marksman use, the SG 550 is equipped with a Kern 4×24

telescopic sight A telescopic sight, commonly called a scope informally, is an optical sighting device based on a refracting telescope. It is equipped with some form of a referencing pattern – known as a ''reticle'' – mounted in a focally appropriate p ...

on a quick-detachable mount. The sight weighs and includes a variety of features, such as STANAG 2324/MIL-STD-1913 compliant mounting components, a

Bullet Drop Compensation A telescopic sight, commonly called a scope informally, is an optical sighting device based on a refracting telescope. It is equipped with some form of a referencing pattern – known as a ''reticle'' – mounted in a focally appropriate pos ...

(BDC) elevation adjustment knob for ranges from 100 to 600 m, a tritium-illuminated

reticle A reticle or reticule, also known as a graticule or crosshair, is a pattern of fine lines or markings built into the eyepiece of an optical device such as a telescopic sight, spotting scope, theodolite, optical microscope or the electronic v ...

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. The basic model of this optical sight was already used on the Stgw 57. The upper receiver can accept quick-detachable

rails Rail or rails may refer to: Rail transport *Rail transport and related matters * Railway track or railway lines, the running surface of a railway Arts and media Film * ''Rails'' (film), a 1929 Italian film by Mario Camerini * ''Rail'' (1967 fi ...

and adapters used to mount optics (STANAG 2324 compliant). The

scope mount Scope mounts are rigid implements used to attach (typically) a telescopic sight or other types of optical sights onto a firearm. The mount can be made integral to the scope body (such as the Zeiss rail) or, more commonly, an external fitting t ...

ing system consists of a centering hole located on the front face of the rear sight assembly and a

dovetail A dovetail joint or simply dovetail is a joinery technique most commonly used in woodworking joinery (carpentry), including furniture, cabinets, log buildings, and traditional timber framing. Noted for its resistance to being pulled apart, a ...

-like mounting point at the front end of the receiver. Swiss Arms (respectively

Brügger & Thomet B&T AG, formerly Brügger & Thomet AG, is a Swiss defence supplier specializing in the design and manufacturing of firearm A firearm is any type of gun that uses an explosive charge and is designed to be readily carried and operated by an ...

) offer several types of quick-release scope mounts and

Picatinny rail The 1913 rail (MIL-STD-1913 rail) is an American rail integration system designed by Richard Swan that provides a mounting platform for firearm accessories. It forms part of the NATO standard STANAG 2324 rail. It was originally used for mount ...

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

Both the rifle and carbine come standard with a spare magazine, sling,

cleaning Cleaning is the process of removing unwanted substances, such as dirt, infectious agents, and other impurities, from an object or environment. Cleaning is often performed for beauty, aesthetic, hygiene, hygienic, Function (engineering), function ...

kit and a loading aid for rapid magazine filling. The full-sized SG 550/551 will accept SIG's 40 mm GL 5040/5140

grenade launcher A grenade launcher is a weapon that fires a specially designed, large caliber projectile, often with an explosive, Smoke screen, smoke, or tear gas, gas warhead. Today, the term generally refers to a class of dedicated firearms firing unitary gre ...

(Swiss military designation: 40 mm ''Gewehraufsatz'' 97), which is mounted under the barrel via an eccentric latch and replaces the lower

handguard A barrel shroud is an external covering that envelops (either partially or full-length) the barrel of a firearm to prevent unwanted direct contact with the barrel (e.g. accidental collision with surrounding objects or the user accidentally touch ...

. The grenade launcher is a single-shot

breech-loaded weapon A breechloader is a firearm in which the user loads the ammunition from the breech end of the barrel (i.e., from the rearward, open end of the gun's barrel), as opposed to a muzzleloader, in which the user loads the ammunition from the ( muzzle ...

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 Aluminium (or aluminum in North American English) is a chemical element; it has chemical symbol, symbol Al and atomic number 13. It has a density lower than that of other common metals, about one-third that of steel. Aluminium has ...

launcher weighs 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

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 no fuller. The bayonets are manufactured exclusively for the Swiss Army by

Victorinox Victorinox () is a knife manufacturer and watchmaker based in the town of Ibach, in the Canton of Schwyz, Switzerland. It is known for its Swiss Army knives. Since its acquisition of rival Wenger in 2005, it has become the sole supplier of mul ...

and in the past by

Wenger Wenger was a Economy of Switzerland, Swiss cutlery manufacturer that exists today as a brand of once-rival Victorinox, used for knives, watches and licensed products. Founded in 1893, it was best known as one of two companies to manufacture Swi ...

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 Solingen (; ) is a city in North Rhine-Westphalia, Germany, 25 km east of Düsseldorf along the northern edge of the Bergisches Land, south of the Ruhr. After Wuppertal, it is the second-largest city in the Bergisches Land, and a member of ...

West Germany West Germany was the common English name for the Federal Republic of Germany (FRG) from its formation on 23 May 1949 until German reunification, its reunification with East Germany on 3 October 1990. It is sometimes known as the Bonn Republi ...

) or the American M9.

Variants

SG 551

The SG 551 carbine has a short pattern barrel, gas tube and piston compared to the SG 550. The SG 551 series rifles have a 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

and detachable cheek riser. * SG 551

SWAT A SWAT (''Special Weapons and Tactics'') team is a generic term for a police tactical unit within the United States, though the term has also been used by other nations. SWAT units are generally trained, equipped, and deployed to res ...

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 barrel that enables the use of rifle grenades and a bayonet.

SG 552 Commando

The compact SG 552 Commando (full designation as the 552-2P) carbine was released in July 1998. It has a shorter 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 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 The AK-47, officially known as the Avtomat Kalashnikova (; also known as the Kalashnikov or just AK), is an assault rifle that is chambered for the 7.62×39mm cartridge. Developed in the Soviet Union by Russian small-arms designer Mikhail Kala ...

: 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 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

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 long sight radius. A long barrel version of the SG 553 known as the SG 553 LB incorporates a barrel with provision to fire rifle grenades and support a bayonet. Further factory options for the SG 553 rifle series are an integrated receiver

and an adjustable butt stock. The SG 553 R is a variant chambered for the 7.62×39mm cartridge fed from AK family box magazines. 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 IWA OutdoorClassics, also referred to as simply IWA, short for ''Internationale Waffen Ausstellung'' (International Weapons Exhibition), is an annual trade fair held in the Messezentrum Nuremberg in Bavaria, Germany for the hunting, shooting spor ...

in 2016.

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.

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. Introduced in 1988, This accurized rifle has a refined two-stage trigger (the pull force was reduced from to , a heavy, hammer-forged 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.

Civilian variants

The SG 550/551/552/553 are also available in 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 mm or 254 mm (1:7 and 1:10 in)

twist rate Rifling is the term for helical grooves machined into the internal surface of a firearms's barrel for imparting a spin to a projectile to improve its aerodynamic stability and accuracy. It is also the term (as a verb) for creating such groov ...

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. Sig 556 Classic

Due to import restrictions, the American civilian market required a partially American-made version assembled by SIG Sauer, Inc. in

Exeter, New Hampshire Exeter is a New England town, town in Rockingham County, New Hampshire, United States. Its population was 16,049 at the 2020 United States census, 2020 census, up from 14,306 at the 2010 census. Exeter was the county seat until 1997, when county ...

. The SIG 556 is designed to meet these requirements. The 556 lacks full-auto capability and the overall length is . One difference is a new

aluminum Aluminium (or aluminum in North American English) is a chemical element; it has chemical symbol, symbol Al and atomic number 13. It has a density lower than that of other common metals, about one-third that of steel. Aluminium has ...

lower receiver that accepts

M16 The M16 (officially Rifle, Caliber 5.56 mm, M16) is a family of assault rifles adapted from the ArmaLite AR-15 rifle for the United States military. The original M16 was a 5.56×45mm automatic rifle with a 20-round magazine. In 1964, th ...

STANAG magazine A STANAG magazine or NATO magazine is a type of detachable firearm magazine proposed by NATO in October 1980. Shortly after NATO's acceptance of the 5.56×45mm NATO rifle cartridge, Draft Standardization Agreement ( STANAG) 4179 was proposed i ...

s and an M4 telescoping buttstock. The barrel's twist rate is 178 mm (1:7 in). 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. Several folding stock models have been released as well as variants with railed forend combinations. Another variant is the SIG 556 DMR featuring a barrel. 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-pattern box magazines was introduced. 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. The SIG 522LR is a .22-caliber sporting rifle styled after the SG 551. It uses a simple blowback 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.

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". 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. The National Firearms Association of Canada considered pursuit of the matter through the legal system. On 31 July 2015, the Canadian government overturned the reclassification and returned the Swiss rifles to the original classifications. On 1 May 2020, in the wake of the Nova Scotia attacks, the rifles were again reclassified as Prohibited Firearms via

Order in Council An Order in Council is a type of legislation in many countries, especially the Commonwealth realms. In the United Kingdom, this legislation is formally made in the name of the monarch by and with the advice and consent of the Privy Council ('' ...

Gallery

Image:Caroline-profile-bipode-p1000509.jpg, With bipod extended. Image:Fass90-bayonette-p1000786.jpg, With

. 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

and accessories.

Users

Notes

References

Bibliography

*''Règlement 53.96 Fusil d'assaut 5.6 mm 1990''

External links

Swiss Arms PE 90 brochureBiggerhammer.net – portal for articles, information and manuals, etc. on the SIG Stgw 57/SG 510/AMT and SG 550 rifle seriesSG 550/551 technical data and test documentationThe SIG SG 550 series – information, manuals and linksSG 550/551 instruction manualSG 552 instruction manualSwiss Armed Forces Stgw 90 manual

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