Bolt Carrier Group fits AR15/M4 compatible style Rifles (i.e.) .223/5.56mm .300 Blackout. – Technical Specs – Mil-Spec dimensions – Bolt Carrier Group Material: Case Hardened 8620 – Steel Finish: Black Nitride. – This advanced low friction coating minimizes the need for lubricants. – Gas Key: 4130 Steel attached with Grade 8 hardware and properly staked into a milled “valley” to ensure proper positioning. – Cam Pin: Hardened 4340 cam pin – Firing Pin: Mil Spec firing pin made of 8740 steel center-less ground and Hard Chrome coated – Bolt Assembly: The Bolt is “true” Mil Spec dimension and external surfaces are CNC ground after heat treat for a precision fit. – Bolt Material: Case Hardened 9310 Steel. – Finish: All Bolt components Black Nitride – Extractor: 4340 Steel Mil Spec – Extractor Spring & O-Ring Combination – MPI: Magnetic Particle Inspected – HPT: High Pressure Test – Made in USA – Carrier fits AR15/M4 compatible style Rifles (i.e.) .223/5.56mm .300 Blackout