The F-1 Firearms DuraBolt Black Nitride direct impingement full auto rated M16/M4 bolt carrier group” for use in AR15 platforms” is compatible with MIL-SPEC receivers and associated components. The bolt carrier and bolt are ground after heat treat to ensure tolerances.
F-1 Firearms DuraBolt, Bolt Carrier Group Assembly, .223 Remington/556 NATO, Nitride Finish, Gold, Fits AR-15 DB-556-TIN
