The Bolt Carrier Group (BCG) is the main component of the action in an AR-15 pattern rifle. As the market has grown, so, too, have the options for this crucial component. There are a ton of variations in materials, mass profiles, finishes, and more out there, so we will stick to what we have to offer in our system. There are a lot of interesting takes in many departments out there, but we tend to stick to low complexity, tried-and-true formulations to maintain the reliability of the system. The old adage "if it ain't broke, don't fix it" holds quite true in this regard. Every carrier machined to full-mass M16-profile and uses materials that are tested and proven to be dependable. Whether your BCG is a part of a complete rifle or selected in the BYOU configurator pages, each one is individually QC-checked and marked. Every bolt head is stripped down and individually checked for headspace and every component of the assembly is individually demagnetized. All three options are fitted with Sprinco® XP-5 extractor springs and enhanced ejector springs. Below is a breakdown of each option.
Standard
- Full-mass, M16-profile 8620 alloy carrier
- 9310 bolt machined from bar stock that is properly heat-treated, shot-peened, Magnetic Particle Inspected (MP), Marked "MPI"
- 4140 billet extractor, heat-treated, shot-peened, Manganese-Phosphate coating
- Billet 4140 gas key, seated with staked Grade-8 fasteners
- H&M BlackNitride+™ finish through the carrier, gas key, and bolt head
This BCG is the standard offering from our J.O.E.™ and DISSIDENT™ rifles. It is quite in-line with the burgeoning industry standard formula, but there are a few things that set it apart from much of what is flooding the market these days.
First, the 9310 bolt is shot-peened and properly heat-treated to give it strength and durability that is on-par, or better in some areas, than the traditional Mil-Spec C158 material. Heat-treating is effectively black magic, so we won't go into great detail about the process here beyond noting that the material can be more brittle and less durable when it is done improperly or, in the case of the cheap options out there, not done at all. C158 has much better baseline characteristics, making it much more "forgiving" as a material for this application; that is to say that it is simpler to be made to meet the expectations of the part. However, with a proper heat treat, 9310 bolts are more than capable of meeting or exceeding the service life expected of the C158 bolts. As an added measure of quality assurance, the bolt heads are also Magnetic Particle Inspected to ensure that there are no microscopic fissures that came about anywhere in the production process.
Second, it has an extractor machined from 4140 bar stock rather than formed through casting or metal injecting molding (MIM). There are many applications, like parts that don't bear load, pressure, or shearing forces, where these processes are great, but an extractor really is not one of them. They are also shot-peened for durability and phosphate-coated to prevent the claw from slipping on slick brass casings.
Lastly, the carrier itself is machined from Mil-Spec 8620 steel and fitted with a billet 4140 gas key that is deeply staked for a steadfast hold on the Grade-8 fasteners. Each carrier assembly is also individually paired with a barrel by checking headspace. The BlackNitride+ finish throughout the assembly by H&M in Akron, Ohio not only improves lubricity, but prevents corrosion through metal treatment rather than a surface-level coating. So, even as the black oxide layer wears off, the shiny metal below will still retain corrosion resistance. As an added benefit, this process is less cost intensive than the traditional phosphate/chrome-lined process found on the Mil-Spec carriers. Combined with the reduced material cost of the 9310, these are a great option to pair with Modern Series barrels for an affordable yet dependable combination.
Mil-Spec
- Full-mass, M16-profile 8620 alloy carrier
- C158 bolt that is shot-peened, Magnetic Particle Inspected (MP), and High-Pressure Tested (HPT), Marked "HPT/MPI"
- Cold drawn and stress relieved extractor that is machined from 4140 Steel per ASTM A108
- Extruded 4130 gas key with staked Grade-8 fasteners
- Heavy Manganese-Phosphate on the exterior surfaces with a hard-chrome lined bolt run and gas key interior
For the shooters that need to meet specific material requirements or simply demand "the old ways", this is the BCG for you. These carriers are pulled from the same lines that fill military contract orders for a variety of vendors. They hold to Mil-Spec materials and finish procedures throughout. While finishes do not necessarily need to match, these pair well with any Classic Series barrel for a rugged, duty-oriented build.
Mil-Enhanced
- Full-mass, M16-profile 8620 alloy carrier
- C158 bolt that is shot-peened, Magnetic Particle Inspected (MP), and High-Pressure Tested (HPT), "MP" Marked
- Cold drawn and stress relieved extractor that is machined from 4140 Steel per ASTM A108
- Extruded 4130 gas key with staked, Grade-8 fasteners with deep splines
- Hard Chrome plating throughout the carrier for maximum durability and lubricity under adverse conditions and ease of cleaning
The Mil-Enhanced bolt carrier is made to military specification just like the Mil-Spec carrier on offer, but the chrome plating typically applied to the internal sections of a traditional BCG is applied throughout the carrier. While it may look similar to a matte Nickel-Boron coating, it is much more durable and will not flake over time as some of those coatings can. Beyond looks, these carriers maintain a baseline lubricity that makes it happier to run longer without additional lubrication than just about anything else out there. When it comes time to clean, the coating makes it incredibly easy to wipe the dirt, carbon, and miscellaneous grime from the interior and exterior surfaces. The main trade-off of this option is cost as the chrome-application process is much more costly than many of the modern coatings on the market today. Is this worth the extra expense? Really, only you can answer that question. In our testing, we have been very impressed with these carriers. With the proven Mil-Spec materials and production processes combined with the improved coating and springs, these are truly "top-shelf" assemblies.