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

    assault rifle (automatic) sig stgw 90 / sg 550 / sg 551 / sg 552 / sg 553 / sig 556
    SIG Stgw 90 / SG 550

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

    In accordance with these requirements engineers SIG (Schweizerische Industrie Gesellschaft) based on the model rifle SIG SG-540 was created assault rifle chambered for the 5.56 x 45 mm, with major modifications concerning the facilitation of weapons.

    new assault rifle, designated SIG SG 550, complied with all the requirements in terms of reliability and accuracy - during testing a new rifle covered with sand, dipped in mud and swamp, with weapons remained militant. Accurancy was even slightly better than Stgw 57, so at a distance of 300 m the mean deviation for the SIG SG 550 is 60-70 mm, while Stgw 57 (SIG SG 510) - 70-80 mm.

    assault rifle (automatic) sig stgw 90 / sg 550 / sg 551 / sg 552 / sg 553 / sig 556
    SIG Stgw 90 / SG 550
    With the grenade launcher mounted GL 5040

    In 1983, the Swiss Army leadership announced the decision SIG SG 550 by the army of Switzerland, but the production, due to funding problems, has been established only in the second half of the 1980s. Therefore assault rifle (automatic) SIG SG 550 was officially put into operation in 1990, received the appropriate designation Stgw 90 (Sturmgewehr 90).

    assault rifle (automatic) sig stgw 90 / sg 550 / sg 551 / sg 552 / sg 553 / sig 556
    SIG Stgw 90 / SG 550
    Partial disassembly Technically

    SIG SG 550 is an automatic rifle with a gas engine automatics, 5.56 x45 mm NATO. Butterfly, locking barrel on the two lugs. The spring is located around the gas piston rod above the barrel and is compressed between the special collar on the rod and the front wall of the receiver. Gas stem its shank is inserted into the frame and fixed with inserted side bolt carrier cocking handle.

    Arm cocking directed slightly upward (for the action of both right and left hand) and is equipped with rubber cap for easy operation at low temperatures.

    gas chamber equipped with gas regulator, which has three positions. Two provisions serve to regulate the gas pressure when shooting in normal or severe conditions (applicable in case of pollution mechanisms weapons sand, snow, etc.). Third position controller completely covers the gas discharge channel and is used to launch rifle grenades.

    trigger - trigger, an interpreter modes of fire, performing the role of a fuse. Translator four-fuse, located on both sides of the receiver. Besides single and automatic fire mode, SIG SG 550 series rifles as well as SG 540, can fire bursts of three shots.

    trigger guard leans on the longitudinal axis to the right or to the left to fire in mittens and launch rifle grenades.

    rifle barrel is made of chrome-nickel steel, cold forging and screwed to the top of the receiver. The trunk is equipped with a flame arrester combined compensator-serving as a guide for the start of rifle grenades.

    assault rifle (automatic) sig stgw 90 / sg 550 / sg 551 / sg 552 / sg 553 / sig 556
    SIG SG 551 SWAT

    receiver is stamped from steel and consists of two halves - the top and bottom, joined by two transverse pins.

    With incomplete disassembly of the receiver removed the rear pin, herewith a box of "break in two" in the front. After removing the charging handle bolt carrier with the bolt removed from the back of the receiver and the gas piston to the rod and the spring are extracted separately after removing the forearm.

    Food weapons carried box magazine capacity of 20 and 30 rounds. Shops made of transparent plastic that allows you to control the number of rounds, and feature on the sidewalls of special clips to connect with each other shops.

    rifle SIG SG 550 is provided with a function of stopping the slide stop valve in the rear position at an empty store.

    assault rifle (automatic) sig stgw 90 / sg 550 / sg 551 / sg 552 / sg 553 / sig 556
    SIG SG 551 LB

    diopter sight is made by type of sight of the German assault rifle G3 (slot with glowing marks for firing at 100 m and diopters at 200, 300 and 400 m), mounted at the rear of the receiver and is regulated in two planes. The front sight mounted on the vapor chamber is provided with ring guard, shooting at night is the second flap fly with light point. In this case the setting of regular Swiss optical and night sights, and application scopes NATO standard STANAG. Export versions of all modifications can be completed commercial optical or collimator sights and later models - the guide type Picatinny rail on the top surface of the receiver, or instead of open sights.

    To reduce weight and size in the SIG SG 550 is widely used high-strength plastic, which are made from the butt, handguard and shops.

    assault rifle (automatic) sig stgw 90 / sg 550 / sg 551 / sg 552 / sg 553 / sig 556
    SIG SG 552 Commando Forearm

    formed by two plastic handguard with slots for better cooling of the barrel.

    In front of the forearm attach lightweight folding bipod, stacked folded into grooves forearm.

    Skeleton butt has a rubber shock absorber at the back and folds right, clinging to the receiver. According to the developers, even with arms folded stock provides high accuracy with hands due to a successful balancing and layout. Cutout in the butt, not only makes it easier, but also allows you to hold it with his left hand while shooting with a bipod.

    rifle is complete bayonet, and also provides an opportunity to mount grenade launcher GL 5040 production SIG.

    Based assault rifle SIG SG 550 has developed a series of modifications.

    Along with the rifle SIG SG 550 was created its modification - rifle SIG SG 551, which differs from the basic model of a short barrel, bipod and lack of bayonet mount and modified flame arrester prevents the use of rifle grenades.

    rifle SIG SG 551 designed to arm the military and police special units, 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.

    assault rifle (automatic) sig stgw 90 / sg 550 / sg 551 / sg 552 / sg 553 / sig 556
    SIG SG 552 Commando In both variants

    SIG SG 551 can be installed rails type Picatinny rail and grenade launcher GL 5140 firm SIG, as well as tactical silencer.

    In 1998, SIG has developed a next modification SG 550 - shortened machine SG 552 Commando, having even shorter barrel and forend than SG 551. Because of the short length of 226 mm barrel and, consequently, short gas piston rod, a return spring 552 located in SG in the receiver, behind the bolt, and the bolt acts directly on the frame and not on the gas piston rod.

    Compact automatic SIG SG 552 Commando, intended for police special forces. Tactical tasks performed by this machine close to the sub-machine gun, and is designed to engage targets at short and medium distances (up to 300 meters).

    SIG SG 552 can be equipped with guide type Picatinny (on the receiver and on the shank) that allows the installation of various tactical devices (lights, hold the handles, etc.). Machine also has a modified form of the flame arrestor.

    Dining SIG SG 551 and SG 552 are often equipped with scopes ACOG, and also have a special attachment to the handguard accessory type flashlight or laser pointer.

    In the early 2000s, was designed by an improved version of the compact machine SIG SG 552, designated SIG SG 553.

    Compact automatic SIG SG 553 outwardly repeats model SG 552 and differs from the previous model except that instead of the return spring 552 SG located in the receiver behind the bolt, and acting directly on the bolt carrier, weapons returned the original design of this site as the model SG 550 and SG 551.

    assault rifle (automatic) sig stgw 90 / sg 550 / sg 551 / sg 552 / sg 553 / sig 556
    SIG 556

    specially for the American market was developed weapons modification SIG 556.

    SIG 556 handguard has changed form and retractable buttstock (like American rifle Colt M4). Magazine well suited for standard shops American M16. Design and operation of the basic units of the machine are identical SIG SG 550.

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

    main differences SIG 556 SWAT from SIG 556 are amended and a new handguard butt production company Magpul. The basic combination of SIG 556 SWAT is supplied with special handle mounted tactical flashlight.

    assault rifle (automatic) sig stgw 90 / sg 550 / sg 551 / sg 552 / sg 553 / sig 556
    SIG 556 SWAT

    Also based on SIG SG 550 sniper rifle designed SIG SG 550 Sniper.

    Especially for the civilian market weapons based rifles SG 550/551/552/553 was launched production of semi-automatic variants SG 550/551/552 SP, PE 90 and SIG Sport, unable to fire bursts.

    In general, a family of machines SIG SG 550 proven one of the best weapons in its class, featuring high reliability, accuracy and ease of shooting in circulation.

    Assault rifles SG 550 series except for the Swiss Armed Forces have been offered for export and adopted a number of European countries.

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

    SG 550 SG 551 SWAT SG 551 LB SG 552 SG 553 SIG 556
    Caliber, mm 5.56x45
    - Butt decomposed
    - The stock closed






    Barrel length, mm 528 363 454 226 226 406
    Weight without magazine, кг4.
    Магазин, count. cartridges 20, 30
    Muzzle velocity
    Bullets м/с
    Эффективная range
    Fire, m
    650 400 550 300 300 500
    Rate of fire,
    Rds / min


Site is a private collection of materials and is an amateur informational and educational resource. All information is obtained from public sources. The administration does not apply for authorship of the materials used. All rights belong to their owners