For those looking for an optic-ready platform, the SIGM400 SRP removes the front sight tower and replaces it with an M1913 railed front gas block. This sight-ready platform allows the operator to mount any optic without worrying about the sight tower. The gas block accepts all iron sights designed to work on the Mil-Spec Picatinny rail. THE SIG M400 SERIES TACTICAL RIFLE, designed for use in law enforcement, military operations, or the sporting field as well as competitive shooting. The SIG M400 is a true AR platform tactical rifle. Provides unparalleled accuracy, with a 16" chrome-lined and phosphate coated barrel that provides maximum durability and corrosion resistance. A 7075-T6 aircraft grade aluminum forged lower receiver adds to the durability and reliability. Features - Direct impingement gas operating system with rotating locking bolt - 5.56 x 45 mm NATO Chrome-lined barrels with phosphate finish - Accepts most M16 type magazines - M16A2 Type flash supressor