Barrel: A proprietary blend of Hammer forged chrome molly vanadium made by FN that is referred to as "Machine Gun Steel" by virtue of its required use in FN's M249 and M240 weapons. The hammer forging process work hardens the steel, making it more durable. In addition, the chrome process for the bore allows for a lining almost twice as thick as a standard M16 for enhanced durability. Chambered in 5.56 NATO, with a 1:7 twist, M4 barrel extension, and a mid-length gas system. This A2 profile barrel is Mil-spec phosphate coated, High Pressure tested and Magnetic Particle inspected. The barrel is finished with a .750" diameter low-profile gas block, PSA 13.5" Hex Full Picatinny M-Lok Free Float Rail, and an A2 flash hider. Upper: Forged 7075-T6 A3 AR upper is hard coat anodized black for durability. Featuring M4 feedramp cuts, these upper receivers are made for us right here in the USA. Includes: Magpul MBUS Sight Set, Black No Bolt Carrier Group or Charging Handle included.