Brownells Ar-15/M16 5.56Mm Bolt Carrier Group, Mpi, Nitride

The Brownells AR-15/M16 5.56mm Bolt Carrier Group (BCG) is a complete, MPI-inspected carrier assembly built to mil-spec dimensions and designed for reliable function in any 5.56 NATO–based AR platform. Whether you're building a new rifle, replacing a worn BCG, or keeping a spare on the shelf, this domestic-made carrier delivers the hard-use durability and tight tolerances that serious shooters expect.

What sets this Brownells BCG apart is the commitment to vertical integration—every component, including the firing pin and gas key, is machined in-house rather than outsourced to the lowest bidder. The bolt is forged from 9310 hardened steel, shot peened, and magnetic-particle inspected to catch subsurface defects. The carrier body is machined from 8620 steel; the gas key is 4130 steel, secured with Grade 8 screws that are properly staked into a precision milled slot to prevent rotation and loosening. The extractor, cam pin, and firing pin are each manufactured to spec from appropriate alloys (4340, 4340, and 8740 steel respectively), with the firing pin center-less ground and hard chrome coated for reliability and longevity. Every BCG is rigorously QC'd for hardness, fitment, cam path geometry, and magnetic-particle inspection before it ships.

This carrier is fully compatible with any AR-15 or M16 rifle chambered in 5.56x45mm NATO, .223 Remington, or 300 AAC Blackout, and comes complete with bolt, carrier, gas key (pre-installed and staked), firing pin, cam pin, firing pin retaining pin, extractor with mil-spec spring, and rubber o-ring. Made in the USA.

Key Features

• Complete bolt carrier group—includes all moving parts and fasteners
• Magnetic-particle inspected bolt for subsurface defect detection
• In-house manufactured components—no outsourced shortcuts
• Mil-spec hardness and dimensions certified in batch
• Gas key staked with Grade 8 screws for secure, non-rotating installation
• Hard chrome coated firing pin for durability and smooth operation
• Made in the USA

Specifications

Frequently Asked Questions

Will this BCG work in my AR-15 or M16?

Yes. The Brownells AR-15/M16 5.56mm BCG is designed for any AR-15 or M16 rifle, and is compatible with 5.56x45mm NATO, .223 Remington, and 300 AAC Blackout cartridges.

What makes this bolt carrier group different from budget alternatives?

Brownells manufactures all components in-house, including the firing pin and gas key, which are often outsourced by other brands. Every BCG is magnetic-particle inspected, hardness tested, and checked for proper cam path geometry and fitment. Materials are certified in batch and dimensions conform to current military specifications.

Is the gas key already installed?

Yes. The gas key comes pre-installed and staked with Grade 8 screws into a milled valley, ensuring it won't rotate or loosen during use.

What components are included?

The complete bolt carrier group includes the bolt, bolt carrier, gas key, firing pin, cam pin, firing pin retaining pin, extractor, mil-spec extractor spring, and black o-ring.