Battle Arms Development BAD-BCG-M16 Laser Engraved BAD INC Logo Bolt Carrier: 8620 Steel Case Hardened, Machined from Billet Firing Pin: 17-4 H-900 Steel, Center-less Ground Gas Key: 4140 Steel with Grade 8 Screws, Properly Staked, Machined from Billet Cam Pin: 4140 Hardened Steel Finish: Black Nitride finished with an ultra-hard, corrosion-resistant top surface layer for wear resistance and minimal need for lubricants. Bolt: 9130 steel Shot Peened, Mil-Spec Dimensions, CNC Ground After Heat Treat, Black Nitride Finished MPI/HPT Extractor: 4140 Billet, Manganese Phosphate Finished for Positive Grip Enhanced: The new bolt carrier geometry was designed to reduce carrier tilt and the key bearing surfaces are relocated to increase reliability.