CMMG 55BA419 M16 Bolt Carrier Group - 5.56x45mm NATO, Black Steel

The CMMG 55BA419 M16 bolt carrier group is a mil-spec replacement BCG built to the original military standard for 5.56x45mm NATO and .223 Remington. Whether you're maintaining an AR platform rifle, building from a lower receiver, or keeping a spare carrier on hand for the range or field, this is a no-frills, proven design that gets the job done. CMMG backs it with a lifetime quality guarantee—confidence that matters when your bolt carrier group is doing the hard work of cycling rounds downrange.

Each component is purpose-built from quality steel: the bolt is machined from 9310 steel with phosphate finish for durability and corrosion resistance, the carrier uses chrome-lined 8620 steel for extended service life and reliable function, and the extractor is 4140 steel phosphate to handle the demanding job of stripping rounds from the magazine and ejecting empties. This is standard mil-spec engineering, which means it'll work reliably in any 5.56mm AR receiver designed to accept M16 internals.

If you're troubleshooting a malfunction, upgrading an older build, or simply keeping a spare BCG in your kit, the CMMG 55BA419 delivers the straightforward quality you expect from a manufacturer that's been in the AR platform game for years. No gimmicks, no fancy coatings—just steel and proven geometry that runs.

Key Features

• Mil-spec M16 design compatible with standard 5.56mm NATO and .223 Remington AR receivers
• 9310 steel bolt with phosphate finish for impact and wear resistance
• Chrome-lined 8620 steel carrier for extended service life and reliability
• 4140 steel extractor with phosphate finish
• CMMG lifetime quality guarantee

Specifications

Frequently Asked Questions

Will this bolt carrier group work in my AR-15?

Yes, the CMMG 55BA419 is a mil-spec M16 BCG designed to function in any standard 5.56mm NATO or .223 Remington AR platform receiver that accepts M16-profile internals.

What calibers does this BCG support?

This bolt carrier group is chambered for 5.56x45mm NATO and .223 Remington. Do not use it in rifles chambered for other calibers such as .308 Winchester or 300 BLK.

Is this a complete bolt carrier group or just parts?

This is a complete, ready-to-install bolt carrier group with the bolt, carrier, and extractor assembly included.

What warranty does CMMG provide?

CMMG backs this BCG with a lifetime quality guarantee covering defects in materials and workmanship.