For the serious AR-15 builder or if you’ve managed to fire your AR-15 so much the bolt carrier group has buildup you just can’t steel brush or clean away, Aero Precision has an answer for you. The M16 Bolt Carrier Group from Aero Precision is machined from a combination of 8620 Tool Steel (Carrier) and 9310 Steel (Bolt) and provides that build from the ground up AR-15 or maintenance of the one you have, a valuable addition.