SIG-556
| Fire rate | 800 rounds/min. |
| Caliber | 5.56 x 45 mm NATO |
| Magazine | 30 rounds |
| Length | 940 mm (37.0 in) |
| Weight | 3.54 kg (7.8 lb) |
| Range | 450 m (1476 ft) |
Description
SIG Sauer, Inc. developed the SIG 556 to comply with United States import restrictions, assembling the firearm in Exeter, New Hampshire. The design was produced as a civilian-market variant of the Swiss SG 550 series. In January 2014, the manufacturer introduced the 556xi series. SIG discontinued the SIG 556, SIG 556R, and 556xi product lines in May 2017.
The rifle operates using a long-stroke gas-piston mechanism. It features an aluminum lower receiver configured to accept STANAG magazines, paired with an M4-style telescoping buttstock. The original variant was built with an aluminum Picatinny rail on the upper receiver and polymer rails on the handguard. Subsequent production introduced the Classic version, which incorporates a slimmer handguard and a hooded front sight.
Variants of this model include the Classic, the DMR, and the P556 pistol. In 2012, the manufacturer introduced the SIG 556R, designed to feed from AK-pattern box magazines; performance issues identified in the first generation of this variant were corrected in later production runs. The firearm is used by several state entities, including the Argentine Federal Police, the Saudi Arabian Royal Navy Special Forces, and the Republic of Korea Coast Guard Special Sea Attack Team.