The CMC Triggers Enhanced Bolt Carrier Group (brand part no. 81631) is a complete AR-15 BCG machined from 8620 steel and finished in black nitride, built to run across .223 Remington, 5.56x45mm NATO, and .300 Blackout chamberings. CMC applies its enhanced surface treatment to improve fatigue strength and wear resistance beyond a standard phosphate-coated carrier, while the nitride process delivers exceptional lubricity and a low friction coefficient for smoother cycling. It is rated to withstand corrosion testing per ASTM spec B117, matching or exceeding the protection of traditional hard chrome-nickel plating at an equivalent or lower cost. Beyond the functional upgrades, the black nitride finish gives the BCG a cleaner, more refined cosmetic appearance than a standard parkerized carrier.

Key Specifications

• Compatible with .223 Remington, 5.56x45mm NATO, and .300 Blackout chamberings.
• Machined from 8620 steel.
• Finished in black nitride for improved fatigue strength and wear resistance.
• Rated for corrosion resistance per ASTM spec B117.
• Lower friction coefficient than a standard phosphate-coated carrier.
• Sold as a complete bolt carrier group.

Frequently Asked Questions

What calibers is this BCG rated for? .223 Remington, 5.56x45mm NATO, and .300 Blackout.

How does the black nitride finish compare to chrome plating? It offers equivalent or better corrosion protection at an equivalent or lower cost.

Buy the CMC Enhanced Bolt Carrier Group

Run a smoother-cycling, corrosion-resistant BCG in your next build. Order this CMC Triggers bolt carrier group from our AR bolt carrier group selection, and our Lubbock, Texas team will get it shipped fast.