AIM AR/M16 BCG-X .223/5.56/.300BLACKOUT caliber 9310 MPI Nitride Bolt NiB Carrier Groups. Features a Black Nitrided, Shot peened, MPI (Magnetic Particle Inspected), 9310 Tool Steel Bolt; 8620 tool steel, enhanced radius cut, Nickel Boron coated M16 carrier; Properly staked, 4140 Machined, Black Nitrided Gas Key fastened with Hardened Grade 8 Fasteners. Extractor includes o-ring.
Assembly