The SIG516 was SIG Sauer's piston-driven AR-15-pattern rifle, using a short-stroke piston operating system while retaining the AR-15's external controls, magazine compatibility, and stock system. Offered in 14.5-inch, 16-inch, and 18-inch configurations with adjustable gas blocks. Discontinued as the MCX superseded it in SIG's rifle lineup. Competes with the LWRC M6 and HK416 in the piston-AR segment. Type: Rifle Action: Semi-Automatic Caliber: 5.56x45mm NATO Capacity: 30 Year introduced: 2010, USA Weight: 7.5 oz Overall length: 35.5" Status: Discontinued Intended use: duty, law_enforcement, patrol