The All-Rounder Carbine Sand Cutter Bolt Carrier Group (ARC BCG) is our individually proof tested and mag particle inspected bolt with an inner diameter bolt run that is machined tighter than competitor offerings. This gives the bolt a ''just right'' gas seal inside of the carrier which increases gas efficiency and service life. Nearly all M16 BCG manufacturers do not compensate for the lack of chrome plating in a TDP bolt carrier, but we make up the difference with our tight tolerance machining. Specifications for Lead & Steel All Rounder Carbine C158 Sand Cutter Complete Bolt Carrier Group: Manufacturer: Lead & Steel Fabric/Material: 4140 Steel Caliber: 5.56mm, .300 AAC Blackout Gun Make: AR Platform Hand: Right Features of Lead & Steel Arc C158 Bolt Carrier Group - Dlc, 5.56Mm, .300Blk, Individual Hp, Mpi Bcg AR-15 .223/5.56/300BO compatible Package Contents: Lead & Steel Arc C158 Bolt Carrier Group - Dlc, 5.56Mm, .300Blk, Individual Hp, Mpi Bcg