Barrel: The 16" 4150V Chrome Moly Vanadium steel Nitride barrel is chambered in 300 Blackout, with a 1:8 twist, M4 barrel extension, and a pistol-length gas system. 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 feed ramp cuts, these upper receivers are made for us right here in the USA. Bolt Carrier Group and Charging Handle not included