The latest incarnation of the SIG556 is a carbine for SWAT operations: the SIG556 SWAT. Like all SIG556 rifles, the SIG556 SWAT uses a full-length gas piston with rotating bolt. It features an aluminum quad-rail hand guard for mounting lasers, lights and other accessories. Designed for close-quarter battle, the SIG556 SWAT has a Swiss-style hinged folding stock. The stock interface is built directly into the trigger casing, and the stock snaps and locks into position with a length of pull that can be preset by the user. Although it was clearly designed for use with CQB optics such as Aimpoint, EoTech and Trijicon, the SIG556 SWAT has rear rotary diopter sights that can be calibrated from close-quarter ranges out to 300 meters.