SIG SG 550
Country: 
SwitzerlandManufacturer: SIG Sauer
Swiss 5.56 NATO (GP 90) assault rifle, adopted by the Swiss Army as the Sturmgewehr 90. Known for accuracy, build quality and the translucent magazines that can be clipped together.
SIG SG 550
Community
Data trust
- Reliability
- Unverified
- Sources
- Sources pending review
Identity
- Designation
- SIG SG 550
- Alias
- Stgw 90
- Manufacturer
- SIG Sauer (Schweizerische Industrie Gesellschaft)
- Country
- Switzerland
- Year
- 1986
- Category
- Assault rifle
- Status
- In service
Ballistics
- Caliber
- 5.56×45 mm NATO (GP 90)
- Muzzle velocity
- 905 m/s
- Rate of fire
- ~700 rpm
- Effective range
- 400 m
- Maximum range
- 700 m
Dimensions
- Barrel length
- 528 mm
- Overall length
- 772 / 998 mm
- Empty weight
- 4.1 kg
Mechanics
- Operating system
- Gas-operated, long-stroke piston
- Bolt / action
- Rotating bolt
Feed
- System
- Translucent clip-together proprietary magazine
- Standard capacity
- 30 rounds
Fire modes
Historical profile
Development and Technological Origins
The development path of the SIG SG 550 began in the 1970s when the Swiss Army identified a requirement to replace the heavy Stgw 57 with a lighter intermediate caliber rifle. The Sturmgewehr 90 program aimed to combine the reliability of the AK-47 action with Swiss precision, leading SIG to refine its previous 540 and 541 series prototypes.
Following a rigorous testing phase against various national and international designs, the SG 541 prototype was officially selected in 1983. However, due to budgetary constraints, full-scale production and final adoption were delayed until 1986, with the first deliveries to units occurring in 1990 under the official designation Stgw 90.
Technical Characteristics and Design
The internal architecture of the SG 550 is based on a long-stroke gas piston system and a rotating bolt, a solution that ensures flawless operation even in arctic climates. The barrel is manufactured using cold hammer forging and features a rifling twist optimized for the Swiss Gw Pat 90 ammunition, although it remains compatible with the standard 5.56x45mm NATO round.
The rifle introduced advanced ergonomic solutions such as the stamped steel receiver, a trigger group with ambidextrous safety, and a two-position gas pressure regulator. The transparent polymer magazines allow for immediate visual checks of remaining rounds and feature lateral studs that enable multiple units to be clipped together without external accessories.
Operational Service and International Variants
Beyond its role as the standard-issue rifle for the Swiss infantry, the rifle was rapidly adopted by numerous global elite units due to its modularity. Shorter versions such as the SG 551 carbine, used by the French Commandos de Marine, and the compact SG 552/553 Commando, fielded by Germany's GSG-9 and several US SWAT teams, represent the pinnacle of close-quarters combat design.
The rifle has demonstrated exceptional resilience during international exercises, maintaining accuracy standards comparable to designated marksman rifles up to 300 meters. Its versatility was confirmed through the implementation of civilian and precision variants, such as the SG 550 Sniper, featuring a heavy barrel and match-grade trigger for law enforcement duties.
Legacy and Influence in the Industry
The SIG SG 550 is considered by many experts to be the finest assault rifle ever produced in terms of build quality and mechanical tolerances. Despite its high production cost, its operational longevity is such that the Swiss Army plans to keep it in service well beyond 2030, periodically updating sighting systems with modern optics and Picatinny rails.
The influence of the 550 is reflected in the development of subsequent SIG Sauer systems, impacting the brand's transition toward more global market-oriented designs like the SIG516 series and the modern MCX. It remains a symbol of Swiss engineering excellence, capable of merging the ruggedness of a military platform with the refinement of a competition weapon.
Variants
Main users
Switzerland · France (GIGN) · Spain · Chile · Vatican (Swiss Guard)
Key components
- ●Stock — Shoulder rest.
- ●Receiver — Weapon body with internal mechanisms.
- ●Grip — Primary grip.
- ●Magazine — Cartridge feed.
- ●Barrel — Guides the projectile.
