The SIG 556 Classic is a US market variant derived from the Swiss SG 550 family, combining Swiss design elements with a semi-automatic operating system suited for commercial sale. It uses a long-stroke gas piston system with a rotating bolt, emphasizing reliability across a wide range of conditions. 

This Classic configuration features Swiss style polymer handguards, a right side folding stock, and diopter iron sights adjustable for elevation and windage. The rifle feeds from standard AR pattern magazines and includes ambidextrous safety controls. Overall ergonomics reflect the original Swiss service rifle while retaining compatibility with widely available magazines and accessories. No original box or accessories included.

Specifications

• Manufacturer: Sig Sauer

• Model: SIG 556 Classic

• Caliber: 5.56x45

• Barrel Length: 16 inch

• Action: Long stroke gas piston, rotating bolt

• Finish: Black

• Handguard: Swiss-pattern polymer

• Stock: Folding polymer stock

• Sights: Diopter rear, protected front post

• Magazines: One 30-round magazine

• Overall Length: ~35.8 inch (stock extended)

• Weight (Unloaded): ~8.5 lb