SIG Sauer SIG 556 5.56 NATO, 16 inch Barrel, Long-Stroke Gas Piston, Collapsible Stock, Flip-Up Sights
USA-made SIG Sauer SIG 556 chambered in 5.56 NATO with the Swiss SG55x lineage and a long-stroke gas piston system. This discontinued model features a two-position adjustable gas regulator, receiver-top MIL-STD-1913 rail with an integrated emergency rear sight, and a flip-up front sight on the gas block. It accepts AR-15/STANAG pattern magazines and includes a collapsible M4-type stock. Condition is very good with an excellent bore.
Condition
Overall Condition: Very good condition, showing only light, superficial signs of prior handling or use.
Bore Condition: Excellent - Clean, mirror finish, no signs of wear.
Bore Rifling: Excellent Rifling - Sharp lands and grooves.
Specific Condition Notes: This firearm is in great shape, with minor superficial scratches and blemishes from handling and storage.
What's Included
- No case included
- Manual
- 1x 30-round polymer AR-15/STANAG pattern magazine (brand not marked)
The SIG 556 uses a proven long-stroke gas piston operating system with a two-position adjustable gas regulator. This design traces its heritage to the Swiss SG55x family while being manufactured in the USA. The result is a robust, piston-driven rifle configured for 5.56 NATO.
Controls and compatibility are straightforward. It accepts AR-15/STANAG pattern magazines and uses a right-side, reciprocating charging handle. A manual safety selector provides familiar operation. Capacity is stated at 30+1 rounds.
Sighting and mounting features are built in. The receiver-top MIL-STD-1913 rail includes a low-profile, flip-up emergency rear sight, and the gas block integrates a matching flip-up front sight. Ventilated polymer fish-gill handguards include short accessory rail segments (lower and small side) for mounting add-ons. A front sling loop sits under the gas block.
The 16 inch barrel is threaded and fitted with an A2-style birdcage flash suppressor. Furniture includes a collapsible M4-type buttstock with SIGARMS logo (approximate LOP 10.5–13.5 inches) and a ribbed polymer pistol grip. Receiver markings note "SIG 556 5.56 NATO; SIG SAUER INC., EXETER, NH, USA." This is a discontinued model.