The Aero Precision PRO Series 5.56 Bolt Carrier Group is built from the ground up to meet the demands of the most extreme conditions. Each component and manufacturing process of the PRO Series 5.56 Bolt Carrier Group was deliberately chosen to increase the reliable service life of the bolt carrier group and its components. Firing Pin: Ground from 8640 Steel Nitride Finish Gas Key: Machined from hardened 4140 steel Torqued to spec with grade 8 hex fasteners Properly staked to Mil-Spec Nitride Finish Cam Pin: Machined from 4140 steel Precision ground after heat treatment Engraved Indexing mark Nitride Finish Mfg: Aero Precision
