With so many Bolt Carrier Groups to choose from, gun writer Rev. Brian Norris deals us his picks for the best AR-15 rifle Bolt Carrier Group or BCG parts.
USA – -(AmmoLand.com)- Some would argue that an AR rifle is an AR rifle.
You hear guys say all the time that all AR-15s are all made in the same factory anyway (which isn’t the case). Those same gents are sure to think that any BCG is a Bolt Carrier Group and any Bolt Carrier Group is a BCG, find the best deal, and plug her in. While there are some great budget BCGs on the market, there are also BCGs out there (like any other AR 15 part) to steer clear of.
Generally, in bolt carrier groups, you should look for Carpenter 158 steel, well-secured gas (using grade 8 fasteners), chrome-lined and nickel boron, and shot-peened. In addition, pay attention to whether the Bolt Carrier Group has been magnetic particle inspected and high pressure tested or not (MPI and HPT for short). These tests assure you that the BCG you purchase has been proven processed correctly. After these tests reveal no fractures, the BCG will prove to be durable for your use.
Bolt Carrier Group (BCG)
We live in an option-rich world. Sometimes those options can become a bit overwhelming. Allow me to guide you to some proven BCG options.
For most users, a standard M16 style BCG will do nicely. That doesn’t quite narrow the field enough, though. Let me point you to some solid budget options that are not the cheapest bolt carrier groups, some mid-range options that have been time tested and shooter approved, and a standout model.
So my cut list of the best BCG goes like this:
- Brownells 5.56 Bolt Carrier Group Nitride MP
- COLT M16 5.56 Bolt Carrier Group
- Bravo Company M16 5.56 Bolt Carrier Group
- Spikes Tactical 5.56 Bolt Carrier Group
- Aero Precision 5.56 Bolt Carrier Group
- Battle Arms Development Enhanced BCG
- Faxon Firearms AR-15 Lightweight 5.56 Bolt Carrier Group
Brownells 5.56 Bolt Carrier Group Nitride MP
This budget option meets the criteria stated above and comes in a nice nitride finish which should perform slightly better than your standard parkerized BCG over time. Actually, I say that it meets the criteria above, but that’s more in the spirit, rather than letter of the law. The steel used is properly hardened, but I don’t think it’s technically Carpenter 158. However, at under $170, an HPT and MPI-tested BCG is a great value. You should know that many would say that 9310 steel is stronger than C158 anyway.
Brownells 5.56 Bolt Carrier Group Nitride MP Product Description:
The Brownells M16 5.56 Complete BCG is designed to work easily and reliably in any AR-15 or M16 rifle chambered in 5.56x45mm, 300 AAC Blackout or .223 Remington.
The Brownells M16 5.56 Complete Bolt Carrier Group is constructed with a bolt made from 9310 steel, which is finished with a heat treatment and shot peening. The carrier is fabricated from 8620 hardened steel. Each element of the bolt-carrier group is finished in a black-nitride coating.
- Magnetic-particle inspected material
- Extractor includes spring and rubber insert
- Includes torqued and staked gas key
- Functions with any cartridge based on the 5.56 NATO cartridge case
The Brownells M16 5.56 Complete BCG comes with a bolt, bolt carrier, gas key, firing pin, cam pin and a firing pin retaining pin.
When discussing the letter of the law type classic BCGs, they don’t get much more classic than Colt. Colt has arguably been the standard since shortly after the AR-15’s inception. As the standard, Colt’s BCG demands a bit of a premium.
COLT M16 5.56 Bolt Carrier Group Product Description:
“Complete, mil-spec assembly with bolt, bolt carrier, and firing pin ready to drop into the rifle or carbine upper of your choice. Each bolt assembly is high pressure tested and magnetic particle inspection tested to ensure it’s free from imperfections that can lead to premature failures. Properly staked gas key prevents gas leakage that can lead to short stroking. M16-style carrier on the black phosphate model has full-length shroud for tripping auto sear, so this carrier may be installed on full-auto law enforcement and military rifles. Carrier and gas key are chrome lined for smooth cycling and resistance to wear from hot combustion gases for years of dependable service.”
In a similar way, a modern AR discussion will typically include components from BCM or Spike’s Tactical. That’s for a good reason. These manufacturers offer exceptional value.
Bravo Company M16 5.56 Bolt Carrier Group
The M16 BCG from BCM is truly made to USGI specifications. BCMs BCGs are not only MPI and HPI tested, but they are also test fired for function. There’s always someone around the water cooler that will promote BCM as the most bang for your buck in the BCG world. Their arguments are strong. As my friend, Tanner would say— they’re not wrong.
Bravo Company M16 5.56 Bolt Carrier Group Product Description:
“BCM® (MPI) complete bolt carrier group is fully assembled. (BCG) Bolt carrier group (auto version) for your AR15, M16, or M4. Parkerized exterior and chrome lined inside carrier. Machined to USGI specifications. This M16/M4 carrier includes the proper Mil-Spec gas key. Gas key is chrome lined and heat treated per GI specifications. Gas key is secured to carrier via USGI domestic mfg Grade 8 fasteners and properly staked per Mil-Specs. These properly hardened parts insure a strong staking and proper gas system functioning. The bolt assembly is machined from the correct Mil-Spec Carpenter No. 158® steel, shot peened for increased strength, includes tool steel machined extractor and ejector, BCM Extractor Spring, and is HPT (High Pressure Tested) and MPI (Magnetic Particle Inspected). Prior to shipping, all BCM Bolt Carrier Groups are test fired for function. As such, the BCG will show handling marks consistent with these quality control procedures. The Flat Dark Earth version has the stripped carrier finished with an Ion Bond coating which lowers friction and allows for easier cleaning.”
The M16 BCG from Spike’s Tactical is typically a few dollars less, it’s made with the same exacting standard in mind, and has a great reputation for reliability. Some would say that it just comes down to whether you want a spider or three letters as a logo on your BCG. Others would argue in perpetuum about the differences they perceive. I’m curious; what do you think?
Spikes Tactical 5.56 BCG Product Description:
“Matched bolt/carrier set is machined to mil-spec dimensions using the latest manufacturing and quality-control techniques to deliver superb reliability in both semi-auto and select-fire rifles. Carrier is hard-chromed inside and has an M16-type full-length shroud on the underside to trip the auto sear on full-auto/burst rifles. Bolt is magnetic particle inspected to ensure there are no internal flaws to compromise structural integrity and cause premature failure. Fully staked carrier key and tool steel extractor further aid reliable cycling. Laser-engraved Spike’s Tactical logo on the side of the carrier is visible when the ejection port door is open. .223/5.56 fits standard AR-15/M16/M4 rifles and is available with standard MIL-STD-171 126.96.36.199 phosphate finish.”
Another very popular brand that is making lots of great quality AR rifle parts is Aero Precision. Their Aero Precision 5.56 BCG is an outstanding entry price black rifle part and has all my basic requirements in a good BCG.
Aero Precision 5.56 Bolt Carrier Group Product Description :
Machined from 8620 steel
Carrier has forward assist serrations
Mil-Spec phosphate coating
Properly staked gas key
Chrome lined gas key and bolt channel
5.56 Bolt is machined from Carpenter 158 tool steel
HPT tested/MPI marked
Black o-ring insert on extractor
High quality BCG
Enhanced Bolt Carrier Groups
In the slightly enhanced BCG category, names like Primary Weapons Systems and Battle Arms Development are often discussed.
If you’re looking for a BCG with a slightly distinct profile (a lightning cut or two), Battle Arms Development is a great option. They’ve cleared out a good reputation in the industry for the quality-made kit. They are made in the USA, have a well-executed black nitride finish, are consistently well-staked, and add a little flair to your AR.
Battle Arms Development Enhanced Bolt Carrier Group Product Description:
“Full Auto M16 Bolt Carrier Group. 9310 Bolt. Shot Peened. HPT & MPI. Staked Gas Key. Black Nitride Finished. For Full Auto Use Made in the USA.”
Faxon Firearms AR-15 Lightweight 5.56 Bolt Carrier Group
Lastly, I’d like to mention a wild card option that’s tailored to the competitive shooting market.
The AR-15 Lightweight Carrier from Faxon appears to be a show stopper. It weighs in at a mere 8.5 oz fully assembled. If you’re looking for a light/ fast option with broad compatibility that’s been held to exacting standards, this may be the ticket. Faxon even uses the QPQ SPN process of salt bath treating their BCG to assure the best possible wear in the worst possible conditions.
Faxon Firearms AR-15 Lightweight 5.56 Bolt Carrier Group Product Description:
“Faxon Firearms set out to create a BCG that could live up to the GUNNER name with no compromise in strength or function. They set specifications that would allow no compromise:
- Lightest Weight Possible (8.5 Ounces Complete)
- MIL-SPEC Materials & Finishes or Better!
- Forward Assist Serrations
- Compatible with Dust Covers
- Maintains Full-Auto Trip Sear for full-auto and the new multi-stage trigger functionality
- Looks Amazing
Matching their barrels, they selected the QPQ method of Salt Bath Nitride for all the carriers’ components. By coating all parts, the carrier’s natural slickness is increased markedly requiring less gas and pressure to operate. Further, the QPQ SBN process seals components against corrosion while making them fantastically wear resistant.
Improvements include using 9310 tool steel for the bolt, which is stronger and nitriding the assembly to increase surface hardness, decrease resistance, and have superior corrosion resistance compared to typical chrome and phosphasted bolt carrier groups. All bolts are fully MPI tested to ensure the material is sound and without defects. Bolt lugs are chamfered 45 degrees to ensure reliable action for even the highest pressure hand loads and fast lightweight actions.
Faxon BCGs are Superfinished to reduce friction, increase smoothness of operation, and reduce fouling. Further, they are full-Auto rated and maintain the trip for full-auto fire control groups and new multi-stage trigger systems. Gas keys use grade 8 fasteners and are fully staked for a lifetime of service.
As a testament of our confidence, the carriers are all laser-engraved with the Faxon Shield after passing all Quality inspections.
- 9310 Tool Steel Construction (Stronger than C158)
- Full MIL-SPEC Heat Treatment
- Shot Peened to MIL-SPEC
- Magnetic Particle Inspection (MPI)
- Back of Lugs Chamfered for Reliability
- Spring, Insert, & “Crane” O-Ring Installed
- QPQ – Salt Bath Nitrided
- S7 Tool Steel Construction
- Fully Heat Treated
- Shot Peened Per MIL-SPEC
- QPQ – Salt Bath Nitrided
Carrier & Key:
- Superfinished Carrier
- Carrier: MIL-SPEC 8620 Steel Material
- Key: 4140 Steel Material
- Fully Heat Treated
- Forward Assist Serrations
- M16 (FULL-AUTO) Compatible
- Grade 8 Fasteners
- Fully & Properly Staked Key, Permatex Sealed
- QPQ – Salt Bath Nitrided
- Weight w/ Key (Not Bolt or any Pins): 6.32 Ounces
4140 Pre-Hardended Steel Material
QPQ – Salt Bath Nitrided”
These options would be welcome additions to any of my ARs. As anyone who knows ARs will tell you, the BCG and barrel are not the components to skimp on. The BCG is the heart of the AR platform rifle. These options will help you keep the blood flow of bullets freely cycling through your weapon. Let me know which one(s) you choose for your AR.
Bonus Video by sootch00: How to I.D. AR 15, M16 & Mil-Spec BCGs
About Brian (Rev) Norris:
Brian (Rev) Norris, in addition to writing and talking guns and gear via video, is a pastor (hence the “Rev”) who specializes in mentoring young men in the urban context. If he catches a moment of free time, you’ll likely find him enjoying his family or heading to the range on his motorcycle. Brian has enjoyed shooting sports since his father introduced them to him as a child. He’s an outdoorsman who enjoys life to the full.