FailZero 450 Bushmaster, Bolt Carrier Group, Silver, No Hammer, Nickel Boron FZ-450-01-NH This Bolt Carrier Group (BCG) comes fully assembled and ready to drop into most mil spec .450 Bushmaster Upper Receivers. All critical parts are coated with EXO Nickel Boron technology that provides permanents dry lubricity" extreme durability" increase wear and corrosion resistance.