The Two-Piece Bolt Carrier Group. The Two Piece BCG is designed to be manufactured on modern equipment using modern materials. Q's BCG consists of 2 sections; The Front-End and The Ass-End The front end is made up of Maraging Stainless Steel dressed in black with a Nitride Coating, and is SCAR-Cut to help prevent bolt bounce. Standard with: Mil-Spec Gas Key and Staking Mil-Spec Bolt Mil-Spec Cam Pin Mil-Spec Firing Pin The Ass-End is naked Stainless Steel, heat treated of course and yes, the overall length is Mil-Spec. The Ass-End holds the firing pin, doing away with pesky firing pin retaining pins. No more broken pins. You're welcome. The Carrier is retained with a single Pin allowing for easy field stripping.