This Aero Precision .308 Complete Black Nitride Bolt Carrier Group BCG is ideal for your big-bore rifle build. These Bolt Carrier Groups from Aero Precision are MPI/HPT inspected and bear a laser engraved Aero Precision logo. The carrier of the Aero Precision .308/7.72 Complete BCG is machined from 8620 steel and then case hardened. All parts of the Aero Precision Complete .308/7.72 Bolt Carrier Group BCG are black nitride coated to reduce friction during use and ensure long-lasting reliable performance. Specifications for Aero Precision .308 Winchester Bolt Carrier Group: Manufacturer: Aero Precision Cartridge: .308 Winchester Hand: Right Condition: New Weight: 18.2 oz Bolt Material: 9310 Steel Carrier Material: 8620 Steel Caliber: .308 Caliber Features of Aero Precision .308 Winchester Bolt Carrier Group BCG: Machined from 8620 Tool Steel (Carrier) and 9310 Steel (Bolt) Finish: Black Nitride - advanced lower friction coating that minimizes the need for lubricants and cleaning Gas Key: 4130 Steel attached with Grade 8 hardware and properly staked Firing Pin: Machined from 8740 steel and hard chrome coated Forward Assist serrations Laser engraved Aero Precision logo Carrier fits AR .308 compatible style AR Uppers and Rifles BOLT FEATURES: Material: Case Hardened 9310 Steel Finish: All bolt components are shot peened and black nitride coated Extractor: Machined from 4340 Steel with double o-rings and double springs Magnetic Particle Inspected and High Pressure Tested High pressure bolt - external surfaces are CNC ground after heat treat for a precision fit and firing pin hole diameter is reduced to .070" Multi-caliber bolt designed to function with .308, 7.62x51, .338 Federal and other .308 based cartridges. Package Contents: Bolt carrier Complete bolt Firing pin Cam pin Retaining pin