The Fulfilled Potential Of The AR-15/M16 in a 10"" pistol One of the most tested and proven weapons systems in the world achieves ultimate refinement with the introduction of the SIG516 rifle. With its Nitride treated, military grade barrel and adjustable, four-position gas regulator, the SIG516 incorporates all of the most desirable mechanical improvements. Add to these a free-floating aluminum forend, and you have the most advanced, versatile AR-based rifle available.Features; Gas piston operating system, Four-Position gas regulator, free-floating military grade Nitride treated barrel, M1913 Picatinny flat top upper, 7075-T6 Aircraft grade aluminum upper and lower receiver with hard coat anodize finish, and flip-up iron sights.