CSC ARMS Nickel Boron Bolt Carrier Group 5.56/.223 and 300 Blackout. Carrier is made out of 8620 steel. Bolt is 9310 steel and HPT/MPI. Gas key is 4140 steel and properly staked. Nickel Boron finish is easy to keep clean and You can run with NO lubrication.
CSC ARMS Nickel Boron Bolt Carrier Group