Barrel: 16" Chrome-moly vanadium steel barrel chambered in 5.56 NATO, with a 1:7 twist rate, M4 barrel extension, and a mid-length gas system. This A2 profile nitride barrel is finished off with a PSA 13.5" Lightweight Hex Full Picatinny M-Lok Free Float Rail, low-profile gas block, and A2 flash hider. Upper: Forged 7075-T6 A3 AR upper is machined to MIL-SPECS and hard coat anodized. Uppers include forward assist and dust cover. These uppers are made for us right here in the USA by a mil-spec manufacturer. Bolt Carrier Group: Full-auto profile bolt carrier group. Shot-peened, mil-spec Carpenter 158 steel bolt. Gas Key Hardened to USGI Specifications, fastened with Grade 8 screws, and Staked Per Mil-Spec. The carrier is 8620 steel M-16 full-auto profile. Includes: Magpul MBUS Sight Set, Black