Tag: Bolt Carrier Group

Aero Precision Nickel Boron 308 AR Bolt Carrier Group

Aero Precision Nickel Boron 308 AR Bolt Carrier Group

Aero Precision Nickel Boron 308 AR Bolt Carrier Group

There are a couple simple reasons to utilize a Nickel Boron 308 AR Bolt Carrier Group in your 308AR and AR-10 rifles. The Nickel Boron Coating by FailZero is super slippery this means the bolt carrier group can operate with much less lubricant, the bolt carrier group will be easier to clean and the coating should allow the bolt carrier group to outlast the weapon under normal operating conditions. Less wear will also occur in the upper receiver. The finish also looks pretty slick.

The Aero Precision upgraded .308/7.62 Nickel Boron 308AR Bolt Carrier Group BCG is an eye catching addition to your AR build. Mil- spec dimensions and coating ensure the highest quality and correct component interface. Visit Aero Precision


  • Carrier is machined from 8620 steel
  • Nickel Boron coated
  • Bolt is machined from 9310 steel
  • MPI
  • Forward Assist serrations
  • Weight: 17.92oz

BCG Includes:

  • Bolt carrier
  • Complete bolt
  • Firing pin
  • Cam pin
  • Retaining pin


Weight 17.92oz

Platform 308AR DPMS

Nickel Boron coating by Fail Zero. Learn more about Fail Zero Nickel Boron Coating Services.

Drop-in bolt and carrier group has a self-lubricating surface that eliminates the need to apply oil or grease that can attract dirt, dust, unburned powder, and carbon and lead to cycling failures. Proprietary EXO-treated Nickel Boron finish produces an exceptionally hard surface that’s 40% more wear resistant than chrome plating, with an ultra-low friction coefficient. Surface is actually harder than the substrate underneath and will not peel, flake, gall, or rub off. EXO-treated Nickel Boron finish bolt/carrier groups have been tested to function reliably without additional lubrication up to 50,000 rounds. Reduced friction also means less heat generated by metal-on-metal contact, so the gun runs cooler and parts last longer. Easy to clean, too—fouling brushes right off. Before treatment, parts are shot peened for surface uniformity and magnetic particle inspected to make sure there are no hidden flaws. Gas key is hardened to USGI specs, chrome lined to resist erosion, and comes already staked to the carrier.

Aero Precision Nickel Boron 308 AR Bolt Carrier Group


DPMS 308 Chrome Bolt Carrier Group

DPMS 308 Chrome Bolt Carrier Group

As more guys dive in to building their own DPMS compatible 308 AR another detail is becoming apparent. These weapons clearly function better out of the box with the chrome bolt carrier group than the phosphate coated counterparts. The reason is simple, lubricity. These weapons have a lot of bearing surface. Bearing surface equates to friction.  This is also why these weapons need a lot more oil when new. Quite simply the chrome bolt carrier group moves much more easily than a phosphate coated one in the upper receiver.

I suspect DPMS has a break in process that starts before a weapon is fired.

DPMS 308 Phosphate Bolt Carrier Group

DPMS 308 Phosphate Bolt Carrier Group

Builds utilizing the phosphate coated bolt carrier group appear to be more prone to not cycling properly with a fresh build.

Now this is not to say the phosphate bolt carriers are bad. They are not. They just need a few boxes of ammunition through the weapon to get all the surfaces polished. Once broken in you would be hard pressed to see any difference in function.

If you already have a phosphate bolt carrier group I would suggest doing the following before heading to the range the first time. (It’s ok do this with the chrome version as well)

  1. Make certain the weapon is unloaded and gun safety rules are followed.
  2. Generously coat the bolt carrier with oil
  3. Coat the bolt lugs with grease
  4. Manually cycle the action 50 or so times or until you notice the action moving smoother. So not “Ride” the charging handle. Let the bolt carrier go with all the velocity and force it can generate. Make no mistake you will see and hear a difference after a short time.
  5. Once satisfied remove the bolt carrier group from the upper and clean everything.
  6. Inspect the bolt carrier group. You will probably notice areas of the carrier getting polished as well as the bolt lugs.
  7. When you get to the range oil and grease as in steps 2 and 3. At this point you should be good to go.


Keep in mind  there can be a significant cost savings with the phosphate coated bolt carrier group. You just need to devote a little time and elbow grease before hitting the range.


As mentioned in a a previous post Brownells has been lstening to what shooters want and they have been adding 308 AR parts almost if not weekly. The latest edition is the JP LOW MASS BOLT CARRIER GROUP JPBC-4BA for 308 AR

JP defies current heavy is better logic of both the AR-15 and AR-308 platforms with the Low Mass Bolt Carriers and in the case of the AR-15 Low Mass Buffer.

I have not seen any analytical data on what system is best in the 308 AR and therefor have no opinion other than JP RIFLES knows the 308 and they have been doing it longer than most. Their rifles constantly win competitions.

I plan on contacting JP for a better explanation.




Here’s what JP says about the LOW MASS system:

We have our own purpose designed operating systems. For the no-compromise competition rifle, the LMOS™ offers the most significant improvement in the felt impulse of the rifle as compared to any modification other than the addition of a compensator. The complete system consists of our low mass bolt carrier and lightweight buffer conversion kit. By reducing the reciprocating mass, the overall impulse as felt by the shooter is further reduced, and bolt velocity is increased without significantly affecting reliability. JP LMOS™ equipped rifles have virtually no reciprocating mass feel.

Reliability with these parts is excellent for competition use. We’ve been using this system for three years without a malfunction at a match. Most shooters that use and maintain this operating system feel that it is a great performance improvement. Some shooters have even reported fewer unexplained flyers in their groups with the JP LMOS™ system.

The JP Low Mass Carrier works out nicely in the new type of civilian machined receivers like ours and the DPMS High and Low Rider series that don’t have a forward assist. Although it doesn’t have the forward assist serrations, it functions in military type receivers. It just won’t allow the use of forward assist on the receiver. Dust cover functions normally.

You may be wondering why our stainless carriers appear black. This is due to a new state of the art surface finish for stainless called QPQ (Quench, Polish, Quench). This is a five-step process resulting in a rock hard surface with natural lubricity. Some want the bright polished look and that is available on the JPBC-3 Low Mass carrier, but not the JPBC-2 tactical carrier.

The JP LRP-07 has our large format AR-10 type Low Mass carrier. The JPBC-4 AR-10 low mass stainless bolt carrier is also finished in black QPQ hard coat for superior wear and natural lubricity. The JPBC-4 will also improve the sight recovery on the DPMS LR-308 or the Armalite AR10. However, it must be used with a DPMS LR-308 bolt assembly, firing pin, cam pin and firing pin retainer.

Do not attempt to use the JPBC-4 with the Armalite bolt assembly, firing pin or cam pin. Unlike the AR-15/M16 platform on which just about everything is cross compatible, each AR-10 type rifle such as the JP LRP-07, DPMS LR-308, Armalite AR-10, Knights SR-25 or Rock River AR-10 is inherently different with only limited cross compatibility of components. Always check compatibility anytime you order aftermarket accessories for AR-10 type rifles.

Stay tuned..