.223/5.56/300BLK Nickel Boron Bolt Carrier Group
.223/5.56/300BLK Nickel Boron Bolt Carrier Group, Nickel boron coated for lubricity and wear resistance advantages over regular nitride coatings. Also helps with carbon cleanup. Machined to exact mil-spec dimensions. Heat treated, shot peened and relief cut. Bolt Features: Carpenter 158 steel Heat treated Shot peened NiB coated MPI tested Bolt Carrier Features: 8620 steel NiB coated NiB coated bore Full auto M-16 style/full mass