SIG SG 556
SIG Sauer, Inc. · Carbine · Discontinued · 2006
Also known as: SIG556, SIG 556
Overview
The SIG SG 556 is a semi-automatic carbine manufactured by SIG Sauer, Inc. of Exeter, New Hampshire, introduced in 2006 as the US-market civilian and law-enforcement version of the Swiss SIG SG 550 series. It retains the SG 550 family's reliable long-stroke gas-piston operating system and rotating bolt, paired with a 16-inch (406mm) chrome-lined barrel chambered in 5.56x45mm NATO. Unlike the Swiss originals, the SG 556 was redesigned to accept STANAG (AR-15/M16-pattern) magazines, feeding from standard 30-round box magazines. It features a side-folding polymer stock, ambidextrous safety, and a Picatinny rail for optics. The platform combines the piston system's reliability with familiar AR-style ergonomics for the American market.
Specifications
| Weight (empty) | 3400 g (119.9 oz) |
| Overall Length | 921 mm (36.26") |
| Barrel Length | 406 mm (15.98") |
| Action Type | Gas Operated Long Stroke |
| Firing Mechanism | Hammer Fired |
| Trigger Type | Single Stage |
| Magazine Capacity | 30 rounds |
| Magazine Type | Detachable Box |
| Muzzle Velocity | 911 m/s (2989 fps) |
| Effective Range | 400 m (437 yd) |
| Barrel Rifling | Right Hand |
| Rifling Twist | 178 mm (7.01") |
| Number of Grooves | 6 |
| Frame Material | Aluminum Alloy |
| Barrel Material | Steel |
| Stock Material | Polymer |
| Finish | Matte Black |
Calibers
- 5.56x45mm NATO · primary · 5.56mm NATO — also known as .223 Remington, 5.56x45mm, SS109, M855
Features
- Firing modes: Semi Automatic
- Feed systems: Detachable Box Magazine
- Safety mechanisms: Manual Safety Selector
- Features: Long Stroke Gas Piston, Rotating Bolt, Chrome Lined Barrel, Side Folding Stock, Picatinny Rail, Stanag Magazine Compatibility, Ambidextrous Safety
Variants
- SIG 556 SWAT — Tactical
- SIG 556 DMR — Designated Marksman
Base model
Service history
Operators
- United States civilian market · adopted 2006
- United States law enforcement
Production
Production years: 2006-2014
Civilian and law-enforcement production by SIG Sauer, Inc. in the United States; exact total unknown.
Origin
Country of origin: United States
Designer: SIG Sauer
Discontinued: 2014
Notes
Marketed by SIG Sauer as the 'SIG556'. Production ran from 2006 until roughly 2014, when it was succeeded by the SIG516 (direct evolution) and later SIG MCX lines. Numerous configurations were offered, including the 556 Classic, SWAT, DMR, Patrol, and a pistol/SBR variant. Early models used SG 550-style proprietary magazines before the switch to STANAG compatibility.
Background
The SIG 556 brought the battle-proven Swiss SG 550 piston system to the American shooter, bridging the European service-rifle lineage with AR-15 magazine compatibility before SIG Sauer's lineup transitioned to the SIG516 and the modular MCX.