Automatic (assault rifle) SIG SG-550 SG-551 SG-552 Stgw.90 (Switzerland)

SIG SG 550

(Sturmgewehr 90) is
assault
rifle manufactured by
Swiss
Arms AG (formerly
Schweizerische Industrie
Gesellschaft
)
from Switzerland.
It is considered one of the most accurate mass-produced assault rifles. [ edit
] Includes standard folding bipod and folding stock.
The rifle has an
AK-47 style firing mechanism and is also known as
FASS 90 ( Fusil
d'
Assaut Standard Suisse
90).
) in French or as Stgw 90
(Sturmgewehr 90) in German.

A variant of this rifle is the SIG SG 551

has been adopted by various US federal agencies due to its reliability and accuracy, as well as by numerous special forces around the world.

SIG 550/551/552 rifles

is that they come with translucent plastic magazines and can be clipped together for faster reloading. There is also a metal piece on the front designed to hold the grenade launcher.

Story

In the 1970s, the Swiss Army began searching for a new small-bore rifle to replace the old 7.5 mm Stgw.57 (SIG 510) automatic rifle. Initial tests were carried out with 5.6 x 48 Eiger and 6.5 x 48 GP 80 cartridges. At the same time, prototype rifles were developed by SIG

(based on their SG-540 design) and the state-owned
Waffenfabrik Bern
(W+F).
. However, for the 5.6mm GP 90

SIG SG 541
rifle over its W+F rival. In 1983, the Swiss Army officially adopted the SIG SG 541 as
the Sturmgewehr-90
, or
Stgw.90
, although due to financial reasons production did not begin until 1986. Today the Stgw.90 is the standard rifle in Switzerland.

The Swiss Army received its last batch of Stgw.90s in the mid-1990s, but these rifles are still offered for export under the designation SIG SG 550

.

Assault rifle (automatic) SIG Stgw 90 / SG 550 / SG 551 / SG 552 / SG 553 / SIG 556

In 1978, the leadership of the Swiss army announced the requirements for a new assault rifle to replace the 7.5 mm caliber Stgw 57 (SIG SG 510) rifle in service: smaller size and weight, the same accuracy at ranges up to 300 m, the ability to create on the basis rifles of a unified family of weapons.

In accordance with these requirements, engineers from SIG (Schweizerische Industrie Gesellschaft), based on the SIG SG-540 model rifle, created an assault rifle chambered for 5.56x45 mm, and the main modifications concerned lightening the weapon.

The new assault rifle, designated SIG SG 550, fully complied with all the requirements for reliability and accuracy - during testing, the new rifle was covered with sand, dipped in a swamp and mud, while the weapon remained combat-ready. The accuracy of fire turned out to be even slightly better than that of the Stgw 57, so at a distance of 300 m the median deviation for the SIG SG 550 is 60-70 mm, while for the Stgw 57 (SIG SG 510) it is 70-80 mm.

In 1983, the leadership of the Swiss army announced the adoption of the SIG SG 550 into service with the Swiss army, but production, due to problems with financing, was established only in the second half of the 1980s. Therefore, the SIG SG 550 assault rifle (automatic machine) was officially put into service in 1990, receiving the corresponding designation Stgw 90 (Sturmgewehr 90).

SIG Stgw 90 / SG 550 partial disassembly
Technically, the SIG SG 550 is an automatic rifle with a gas automatic engine, caliber 5.56x45 mm NATO. The bolt is rotary, locking the barrel with two lugs. The return spring is located around the gas piston rod above the barrel and is compressed between a special collar on the rod and the front wall of the receiver. The gas rod is inserted into the bolt frame with its shank and secured using the bolt cocking handle inserted into the bolt frame from the side.

The cocking handle is directed slightly upward (for use by both right and left hands) and is equipped with a rubber cap for ease of operation at low temperatures.

The gas chamber is equipped with a gas regulator, which has three positions. Two positions serve to regulate gas pressure when shooting in normal or difficult conditions (used in case of contamination of weapon mechanisms with sand, snow, etc.). The third position of the regulator completely blocks the gas outlet channel and is used to launch rifle grenades.

The trigger mechanism is a trigger mechanism, with a fire mode translator, which also serves as a fuse. The safety switch is four-position, located on both sides of the receiver. In addition to single and automatic fire modes, the SIG SG 550, like the SG 540 series rifles, can fire in bursts of three shots.

The trigger guard tilts on the longitudinal axis to the right or left for shooting with mittens and launching rifle grenades.

The rifle barrel is made of cold-forged chrome-nickel steel and is screwed into the upper part of the receiver. The barrel is equipped with a combined compensator-flame suppressor, which also serves as a guide for launching rifle grenades.

The receiver is stamped from steel and consists of two halves - upper and lower, connected by two transverse pins.

During incomplete disassembly, the rear pin is removed from the receiver, and the box “breaks” in the front part. After removing the charging handle, the bolt carrier and bolt are removed from the receiver backwards, and the gas piston with rod and return spring are removed separately after removing the forend.

The weapon is fed from box magazines with a capacity of 20 and 30 rounds. The magazines are made of transparent plastic, which allows you to control the number of cartridges, and are equipped with special clips on the side walls for connecting the magazines to each other.

The SIG SG 550 rifle is equipped with a bolt stop function that stops the bolt in the rear position when the magazine is empty.

The combined diopter sight is made like the sight of the German G3 assault rifle (a slot with luminous marks for shooting at 100 m and diopters at 200, 300 and 400 m), mounted on the rear of the receiver and adjustable in two planes. The front sight, mounted on the gas exhaust chamber, is equipped with an annular fence; for shooting at night, there is a second folding front sight with a luminous dot. This provides for the installation of standard Swiss optical and night sights, as well as the use of NATO sights of the STANAG standard. Export versions of all modifications can be equipped with commercial optical or collimator sights, and later models can be equipped with a Picatinny rail-type guide on the upper surface of the receiver, together with or instead of open sights.

To reduce weight and size, the SIG SG 550 widely uses high-strength plastic, from which the stock, forend and magazines are made.

SIG SG 552 Commando
The handguard is formed by two plastic barrel linings with slots for better barrel cooling.

In the front part of the forend, lightweight folding bipods are attached, which are placed in the folded position in the grooves of the forend.

The frame stock has a rubber shock absorber on the back of the head and folds to the right, pressing against the receiver. According to the developers, even with the stock folded, the weapon provides high accuracy in hand-held shooting due to successful balancing and layout. The cutout in the stock not only makes it lighter, but also allows you to hold it with your left hand when shooting from a bipod.

The rifle is equipped with a bayonet, and also has the ability to mount an under-barrel grenade launcher GL 5040 manufactured by SIG.

A number of modifications have been developed based on the SIG SG 550 assault rifle.

Together with the SIG SG 550 rifle, a modification was created - the SIG SG 551 carbine, which differs from the base model in a shortened barrel, the absence of a bipod and bayonet mount, as well as a modified flash suppressor that does not allow the use of rifle grenades.

The SIG SG 551 carbine, designed for arming military and police special forces, is available in two versions: - SG 551 SWAT - has a barrel length of 363 mm; - SG 551 LB (Long Barrel) - has a barrel length of 454 mm, which allows firing rifle grenades.

SIG SG 552 Commando
Both versions of the SIG SG 551 can be equipped with Picatinny rail type guides and a SIG GL 5140 under-barrel grenade launcher, as well as a tactical silencer.

In 1998, SIG developed another modification of the SG 550 - the shortened SG 552 Commando assault rifle, which has an even shorter barrel and fore-end than the SG 551. Due to the short barrel 226 mm long and, as a consequence, the short gas piston rod, the return spring of the SG 552 is located in the receiver, behind the bolt carrier, and acts directly on the bolt carrier, and not on the gas piston rod.

The compact SIG SG 552 Commando assault rifle is designed for police special forces. In terms of the tactical tasks it performs, this machine gun is close to submachine guns and is designed to hit targets at short and medium distances (up to 300 meters).

The SIG SG 552 can be equipped with Picatinny-type rails (on the receiver and on the forend), which allows the installation of various tactical devices (flashlights, hold handles, etc.). The machine gun also has a modified flame arrester.

The SIG SG 551 and SG 552 variants are often equipped with ACOG sights, and also have special mounts on the forend for accessories such as a flashlight or laser designator.

In the early 2000s, an improved version of the compact SIG SG 552 assault rifle was developed, designated SIG SG 553.

The compact SIG SG 553 assault rifle is completely identical in appearance to the SG 552 model and differs from the previous model only in that instead of the SG 552 return spring, located in the receiver behind the bolt frame and acting directly on the bolt frame, the weapon is returned to the original design of this unit, like models SG 550 and SG 551.

The SIG 556 modification was developed specifically for the American weapons market.

The SIG 556 has a reshaped forend and a retractable stock (similar to the American Colt M4 carbine). The magazine receiver is adapted for standard magazines of the American M16 rifle. The design and operation of the main components of the machine are identical to the SIG SG 550.

In addition to the SIG 556, the SIG 556 SWAT was created.

The main differences between the SIG 556 SWAT and the SIG 556 are a modified handguard and a new stock manufactured by Magpul. In the basic combination, the SIG 556 SWAT is equipped with a special handle with a tactical flashlight installed.

In addition, the SIG SG 550 Sniper sniper rifle was created on the basis of the SIG SG 550.

Especially for the civilian weapons market, based on the SG 550 / 551 / 552 / 553 rifles, the production of semi-automatic variants SG 550 / 551 / 552 SP, PE 90 and SIG Sport, which are not able to fire in bursts, was launched.

In general, the SIG SG 550 family of assault rifles have proven themselves to be one of the best weapons in their class, featuring high reliability, shooting accuracy and ease of use.

Assault rifles of the SG 550 series, in addition to the Swiss Armed Forces, were offered for export and adopted by a number of European countries.

The production of the SIG SG 550 family in Switzerland was established by SWISS ARMS AG (until 2000 SIG Arms AG), and the SIG 556 assault rifle in the USA by a subsidiary of SiGARMS, Inc.

Options [1]

• SIG SG 550 Sniper
  : Sniper version. With bipod, optical sight and specific barrel.
• SIG SG 551
  : Carbine.
  It has a shorter barrel than the SG 550, a modified handguard, and the bipod removed. With these modifications it is not possible to install a grenade launcher or bayonet, but it is prepared for use in special forces and security. SIG SG 551-1P
  : equipped with a Hensoldt 6x42 GL optical sight and detachable cheekpiece.
• SIG SG 551 SWAT
  : Corrosion resistant finish and equipped with a scope such as the Trijicon ACOG 3.5x35. It can also accept accessories for tactical missions, such as a laser pointer or flashlight.
• SIG SG 551 LB
  : This version has the longest barrel and allows the use of grenade launchers.

Civil options

SG 550/551/552/553 are also available only in semi-automatic mode, aimed at the civilian market. Among these variants we find the SG 550/551/552 SP

,
PE 90
and
SIG Sport
. The SG 550 series is available with barrels with two rifling pitches: 178 mm or 254 mm. Rifles designated SG 55x-1 have a pitch of 254 mm, while models designated SG 55x-2 have a pitch of 178 mm. Standard GP 90 ammunition is optimized for the original pitch of the 254mm Swiss rifle.

SIG 522LR

is a 5.5mm semi-automatic sporting rifle chambered in the .22 Long Rifle cartridge, based on the SG 551. It operates by single recoil and has a barrel with a rifling pitch of 406mm per revolution. Due to its operating system, it does not share any parts with other SG 550 series variants. The SIG522 supports the most readily available chargers of the type used in AR to .22 caliber conversions.

Automatic (assault rifle) SIG SG-550 SG-551 SG-552 Stgw.90 (Switzerland)

Family of SIG55x assault rifles, from top to bottom: SIG SG 550 / Stgw.90, SIG SG 551-LB SWAT,SIG SG 551 and SIG SG 552 SWAT

Automatic (assault rifle)SIG SG 550 / Stgw.90, left view

Short assault rifle (assault rifle) SIG SG 551 SWAT with accessories (Trijicon ACOG sight, flashlight, front grip)

Compact assault rifle (assault rifle) SIG SG 552 SWAT with accessories

The SG-550 assault rifle (automatic) was developed in 1979-1980 by the Swiss company SIG to participate in the competition for a new assault rifle for the Swiss army (to replace the SIGStgw.57 assault rifle of 7.5x55 caliber). The SIG SG-550 assault rifle was created on the basis of the SIGSG-540 and SG-541 models that preceded it, with the main modifications relating to lighter weapons. In 1983, the SIG SG-550 was officially adopted by the Swiss Army under the designation Stgw.90, but production did not begin until 1986 due to funding problems. Later, based on the SG-550, the SG-551 carbine and the shortened SG-552 assault rifle were developed, as well as their civilian versions, which were not able to fire in bursts. In general, the SIG SG-550 family of assault rifles are among the best in their class, featuring high reliability, shooting accuracy and ease of use.

The SIG SG-550 assault rifle is built on the basis of a gas exhaust engine, and is locked by turning the bolt to two lugs. The return spring is located around the gas piston rod above the barrel and is compressed between a special collar on the rod and the front wall of the receiver. The gas rod is inserted into the bolt frame with its shank and secured using the bolt cocking handle inserted into the bolt frame from the side. The receiver is stamped from steel and consists of two halves - upper and lower, connected by two transverse pins. The barrel is screwed into the top of the receiver. During incomplete disassembly, the rear pin is removed from the receiver, and the box “breaks” in the front part. After removing the charging handle, the bolt carrier and bolt are removed from the receiver backwards, and the gas piston with rod and return spring are removed separately after removing the forend. The trigger mechanism is a trigger mechanism, with a fire mode translator, which also serves as a fuse. If necessary, a separate independent module can be installed in the trigger, providing firing with a cutoff of 3 shots. The gas exhaust chamber has a three-position gas regulator - 2 positions for firing in normal and difficult conditions and a third for firing rifle grenades (the gas exhaust channel is closed). The barrel is equipped with a combined compensator-flame suppressor, which also serves as a guide for launching rifle grenades. Sights include a front sight on a gas exhaust chamber and a rear sight of a drum design with a set of diopter holes for different firing ranges. The forend is made of plastic, and underneath there is a removable lightweight folding bipod. The stock is plastic, skeletal, folding to the side. The SG-550 can be equipped with a bayonet and a mount for an optical sight. In the Swiss army, Stgw.90 assault rifles are sometimes equipped with a 4X sight; export versions of all modifications can be equipped with commercial optical or collimator (“red dot”) sights. Automatic rifles of modern releases can be equipped with a Picatinny rail type guide on the upper surface of the receiver, together with or instead of open sights. The SG-551 SWAT and SG-552 variants are often equipped with ACOG sights, and also have special mounts on the forend for accessories such as a flashlight or laser designator.

The SG-551 carbine differs from the base model only in a shortened barrel and a modified flash suppressor, which does not allow the use of rifle grenades, as well as the absence of a bipod and the impossibility of installing a bayonet.

The shortened SG-552 assault rifle has an even shorter barrel and fore-end. Due to the short barrel and the resulting short gas piston rod, the SG-552's recoil spring is located in the receiver, behind the bolt carrier, and acts directly on the bolt carrier rather than the gas piston rod.

Users

• Germany - used by the anti-terrorism unit GSG 9 of the German Federal Police.
• Argentina - SIG SG 552 Commando is used by the anti-terrorist unit of the Special Federal Operations Group of the Argentine Federal Police and the special unit of the Grupo Albatros of the Argentine Naval Prefecture.
• Brazil - Used by the Federal Police and Air Force.
• Canada - used by the police.
• Chile - The FAMAE factory produces rifles and parts in the 540 and 550 families. [3] It was also the standard rifle of the Chilean Army until the introduction of the Galil ACE assault rifle. [ 4 ] [ ] [ ]
• Costa Rica - Used by the Costa Rican border police, they are deployed on the northern border with Nicaragua.
• South Korea - used by special forces.
• Denmark - intelligence services
• Egypt - used by special forces.
• Spain - Special Operations Group (GEO): SIG 551
  SWAT,
  SIG 552
  Commando
• USA - Used by some federal agencies.
• Finland - Used by some police forces.
• France - used by special forces.
• India - used by special forces.
• Indonesia - used by special forces.
• Italy - used by the Carabinieri
• Macau - Used by some security forces.
• Malaysia - used by special forces.
• Malta - used by the armed forces
• Netherlands - used by the coast guard.
• Pakistan - Used by some police forces.
• Poland - used by special forces.
• Romania - used by special forces.
• Serbia - used by special forces.
• Slovakia - used by the Carabinieri
• Switzerland - The SIG SG 550 is the standard service rifle of the Swiss Armed Forces and is also offered for export.
• Taiwan - Usado por la unidad especial de la policía, Police Department of the Ministry of Internal Affairs of the Security Service.
• Türkiye - used by special forces.
• Tunisia - Used by some security forces.
• United Kingdom - Used by some security forces.
• Vatican City - SIG 552 is used by the Pontifical Swiss Guard.
• Venezuela - Used by the Venezuelan Navy Special Operations Unit.
• Mexico - Used by police in various states.

References

1. "Modern Firearms - SIG 550/551/552". world.guns.ru
   . Retrieved January 10, 2016
2. G&G Armament. Office directory
   . Almeria. |fechaacceso=required |url=(help)
3. Innovative projects. Rifle SIG556 FAMAE - SIG SAUER. Archived December 28, 2011, at the Wayback Machine.
4. https://www.infodefensa.com/latam/2014/06/19/noticia-famae-presentan-paris-nuevo-fusil-asalto-ejercito-chile.html
5. https://www.infodefensa.com/latam/2014/08/08/noticia-famae-presenta-primeros-fusiles-galil-coproducidos-ejercito-chile.html
6. https://www.infodefensa.com/latam/2015/04/16/noticia-falerías-maestranzas-ejercito-chile-presenta-galil-version-actualizada-fusil.html