Sig Sauer SIG 556 5.56 NATO Semi-Auto Rifle, 16 in Barrel, Piston System, Folding Sights, 30+1
This U.S.-made SIG 556 is a semi-automatic derivative of the Swiss SG 550/551 family, built around a long-stroke piston with a two-position adjustable gas regulator. It features a receiver-length Picatinny rail, folding iron sights, a threaded 16-inch barrel with an A2-pattern flash suppressor, and AR/STANAG magazine compatibility. The rifle pairs a pressed-steel upper with a 7075-T6 forged aluminum lower, finished in matte black.
Condition
Overall Condition: Very good condition, showing only light, superficial signs of prior handling or use.
Bore Condition: Good - Clean, well-maintained, minor wear marks.
Bore Rifling: Good Rifling - Intact, well-defined lands and grooves.
Specific Condition Notes: The firearm is in solid functional shape. External surfaces show scattered scratches and blemishes.
What’s Included
- Sig Sauer SIG 556 semi-automatic rifle
- 1 polymer AR-pattern 30-round detachable magazine (STANAG-compatible)
The SIG 556 operates via a gas-operated, long-stroke piston system with a two-position adjustable gas regulator, reflecting its SG 550/551 lineage. This setup supports reliable cycling across varying conditions and ammunition types while maintaining the platform’s distinctive ergonomics and manual of arms.
Construction pairs a pressed-steel upper receiver with a 7075-T6 forged aluminum lower, both finished in matte black. Controls include a right-side charging handle and a manual safety selector. The 16-inch barrel is threaded and fitted with an A2-pattern flash suppressor.
Furniture consists of a ventilated polymer handguard, a ribbed polymer pistol grip, and an M4-style 6-position telescoping stock. Length of pull is adjustable to approximately 11–14 inches, offering a straightforward fit across different shooters and gear setups.
Sighting and mounting options include a receiver-length Picatinny rail, a flip-up front sight on the gas block, and a folding rear sight on the receiver rail. The rifle accepts AR/STANAG pattern magazines; capacity is 30+1, and one 30-round magazine is included.
Markings read: "SIG 556 5.56 NATO. SIG SAUER INC., EXETER, NH, USA". This U.S.-produced model comes from a SIG 556 line that was later discontinued, adding clear context to its place in the platform’s evolution.