FailZero Bolt Carrier Group, 7.62X39, Nickel Boron Coated, No Hammer FZ-7.62X39-01-NH This 7.62x39 Bolt Carrier Group (BCG) comes fully assembled and ready to drop into most mil-spec upper receivers chambered in 7.62x39. All critical parts are coated with EXO Nickel Boron technology that provides permanent dry lubricity" extreme durability and increases both wear and corrosion resistance.