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Mil-spec M16 BCG assemblies available for completing (or upgrading) your AR-15.

You can't -- really, shouldn't -- reinvent the wheel. But you can always put better tread on it. That's why we're offering up M16 bolt carrier groups with improved, heat-treated 9310 bolts, mil-spec 8620 carriers, and new nitride treatments that provide better wear and rust resistance and natural lubrication compared to phosphate and chrome lining. Every gas key on every BCG we sell is heat-treated and nitride-treated, too, before being fastened with Grade-8 fasteners that are each properly staked.

Want to know more? Check out the AR Bolt Carrier Group Guide.

.308 and 9mm AR Bolts Available

Building a 9mm AR pistol? Or a bench-ready .308 or 6.5 Creedmoor rifle? Grab a quality bolt carrier group to complete your build. Our 9mm BCGs are compatible with all available 9mm uppers, lowers, build kits, and other 9mm AR parts we sell. Available 9mm bolts are also ramped and work with PSA 9mm upper assemblies. All .308 parts, uppers, lowers, and components are also compatible with our available .308 nitrided BCG.

Our Bolt Carrier Specs:

  • Heat-treated 9310 bolts
  • Heat-treated gas keys
  • Mil-spec 8620 carriers
  • Gas keys are staked
  • Grade-8 fasteners
  • S7 tool steel extractors
  • Upgraded nitride QPQ treatment
  • Better corrosion resistance than phosphate
  • Better thermal protection than chrome-lining
  • Manufactured by experienced gunsmiths in the USA

 Why a 9310 bolt instead of Carpenter No. 158?

Just because something is "mil-spec" does not mean it's optimal, or even nearly the best choice, when it comes to overall performance and quality. Mil-spec simply means that a particular tool, alloy, or component adheres to basic standards. That's the case with the old Carpenter 158 steel originally used to craft mil-spec bolts. 

Enter 9310. This is an AISI standard grade of tool steel that, when properly heat-treated, is approximately 7% stronger than Carpenter 158. With heat treatment, 9310 provides a slightly higher toughness that improves fatigue life of the bolt - an important quality, considering the bolt experiences the most heat and pressure from the AR's direct-impingement gas system. Importantly, 9310 also provides better corrosion resistance than C158, which allows it to withstand all that carbon fouling present in the gas system. In combination with nitride quenching, these 9310 bolts outperform the old "mil-spec" standard.

Need help with install or maintenance? How's how to disassemble your BCG.

"Is an M16 bolt legal?"

Yes. Owning an M16 bolt, and using one in your AR-15, regardless of its configuration, is entirely legal. Using an M16 BCG will not make your AR rifle or pistol fully automatic. Why use one? Because it's a tougher, better bolt. Simple. That's why we include an M16 BCG in all of our build kits. The added mass of the M16 bolt carrier body also helps to reduce felt recoil, providing more inertia against the force of the bolt being pushed by the gas system.

DISCLAIMER: If you are new to the world of DIY gun building, you likely have a lot of questions and rightfully so. It’s an area that has a lot of questions that, without the correct answers, could have some serious implications. At, we are by no means providing this content on our website to serve as legal advice or legal counsel. We encourage each and every builder to perform their own research around their respective State laws as well as educating themselves on the Federal laws. When performing your own research, please be sure that you are getting your information from a reliable source.

We are a national retailer of individual components and not all products depicted on this website are legal in every state. Shipping of various products found on this website are prohibited to some states (such as California, Connecticut, District of Columbia, Hawaii, New Jersey, New York, Rhode Island, and Washington). The information, pictures, text or products presented on this website are not a representation by us, and should not be understood by you, that any product or completed firearm is legal to assemble or own in your state of residence. We encourage each and every builder to perform their own research about the state and federal laws that apply to them. It is your responsibility to understand the law and we encourage you to consult with an attorney or your local ATF representative.