Are you currently looking to improve your AR-10 with a new bolt carrier group? If so, you’ve come to the right place.
Best Budget Pick: Brownells .308 AR Bolt Carrier Group
The Brownells .308 AR Bolt Carrier Group is designed to function well with nearly every caliber the AR-10 is made for despite having .308 in its name. It’s built out of a very tough and durable 8620 steel and has a blackened nitride finish that is both surface wear resistant and corrosion resistant as well.
Best Value Pick: CMMG .308 Bolt Carrier Group
The CMMG .308 Bolt Carrier Group is a solid value for the money thanks to its durable 8620 steel construction and the fact that it has been optimized for the .308 Winchester and 7.62x51mm NATO rounds. It has a phosphate finish coated over the 8620 steel, which gives it a very rough look but is also very resistant to rust and corrosion.
Best Overall Pick: JP Enterprises .308 AR Low Mass Bolt Carrier Group
The JP Enterprises .308 AR Low Mass Bolt Carrier Group is a solid pick for an AR-10 bolt carrier group due to the fact that it is very lightweight without sacrificing durability, as it comes with a very rust resistant chromium nitride finish and Melonite QPQ finish. This bolt carrier group was also designed by JP Enterprises to function well with AR-10s that come with adjustable gas tuning systems.
The bolt carrier group is one of the most integral elements to any AR-style rifle, and without it, your AR-10 would not even be able to function in the first place.
In this guide, we’ll dive into what’s included in a bolt carrier group in case you didn’t already know, the top qualities to look for in a bolt carrier group, and then our recommendations for the top three best bolt carrier groups for 2020.
Why Go With The AR-10?
Why should you go with an AR-10 in the first place? It all comes down to one simple reason: the AR-10 is one of the most practical and versatile rifles that you can own.
From long range precision shooting to big game hunting to self-defense to tactical use, an AR-10 can do virtually everything that you need a rifle to do. If anything, a solid argument can be made that the AR-10 is the one rifle to have if you could only own one.
The AR-10 is a semi-automatic rifle with a detachable box magazine designed to fire larger rifle rounds like the 6.5 Creedmoor or the .308 Winchester. It’s essentially the larger cousin to the AR-15, which fires intermediate rifle rounds.
The AR-10 is a more practical weapon than the AR-15 overall due to the fact that it hits harder, can shoot farther, and can bring down larger game. The primary advantages of the AR-15, on the other hand, are its lighter recoil and greater magazines size due to the smaller rounds that it fires like 5.56x45mm NATO.
Granted, there are many other semi-automatic rifles with detachable box magazines that fire larger rounds as well. Examples include the Springfield M1A, the FN FAL, and the HK G3. The big advantage that the AR-10 has over each of these rifles are that it is very customizable just like the AR-15. In fact, certain components between the AR-10 and the AR-15 are even compatible with one another.
If you want a rifle that is accurate, practical, versatile, reliable, and customizable, the AR-10 is the rifle that you’re looking for. And if you want to improve the function of your AR-10 after you buy one, one of the very best things you can do is to upgrade the bolt carrier group, or BCG.
Not upgrading but instead starting a new build? Read our article on AR-10 Build Kits, they might be a good option for you!
What is Included In A Bolt Carrier Group?
A major question you probably have is: what’s included in the bolt carrier group to begin with? We’ll answer that question now.
The bolt carrier group is located in the upper receiver of your AR-10. You can slide it in or out after removing the pin that holds the upper and lower together. Swing the upper upwards after removing the pin to remove it from the AR-10 lower, and then you can access the bolt carrier group through the rear of the upper.
The bolt carrier group is absolutely integral to enabling your AR-10 to function. Each time you fire your AR-10, the gases from the spent round will be sent down the gas tube to the bolt carrier group. When the gases fill up the chamber in the bolt carrier group, the entire group as a whole will be forced to the rearwards against your rifle’s recoil spring.
As the bolt carrier travels to the rear, it will twist and unlock from the chamber. This permits the entire action of the rifle to cycle to the rearward. The spent shell casing will be ejected through the ejection port, and a new round will be loaded from the magazine into the chamber.
Without the bolt carrier group, your AR-10 literally could not function because the firing pin could not strike the primer of the round and the action could not cycle back.
Here are the primary components that make up each bolt carrier group:
Too many people confuse the terms ‘bolt carrier group’ and ‘bolt carrier’ together. The reality is that the bolt carrier is a part of the bolt carrier group as a whole. This is also why the abbreviation BCG is used to refer to the bolt carrier group.
The bolt carrier houses all of the pieces of the bolt carrier group. It’s usually built out of hardened steel (such as 8620 steel and 9310 steel) and absorbs the force of the gas from each fired round.
The carrier key, also known as the gas key, is located at the top of the bolt as a protrusion. It’s hollowed out and absorb the gas that travels down the gas tube of the AR when it fires. If the carrier key did not exist, the extractor and bolt of the AR-10 could not rotate.
Bolt Gas Rings
The bolt gas rings are designed to trap gas of each spent round, thus allowing the bolt to work. If the bolt gas rings did not exist, the gas of each round would simply disperse throughout the upper receiver. The action would thus not be able to cycle back.
Bolt and Extractor
The bolt and extractor serve together as a single unit but serve dual functions. The extractor is designed to hook onto the outer rim of each round and holds them in place when loading them from the magazine into the chamber. When the round is fired and the action of the rifle cycles back, the extractor continues to hold onto the round by the rim until it is ejected through the ejection port. A new round is then loaded from the magazine.
Meanwhile, the bolt resembles a star and is located on the front of the bolt carrier group. IT allows the overall bolt carrier group to lock or unlock. When a round is fired, the bolt will rotate by fifteen degrees in order to free up the overall bolt carrier group and permit it to cycle back.
The firing pin strikes the primer of a round each time the trigger is pulled. The pin is located at the head of your bolt, and without it, the gun could not fire.
While it’s the bolt that rotates to free up the bolt carrier group and permit to move rearward, it’s the cam pin that prevents the bolt from rotating too far. The cam pin is located in the carrier in a hole next to the bolt.
How To Install A Bolt Carrier Group In An AR-10
In order to install a bolt carrier group into our AR-10, you’ll need to follow these steps:
- Drop down the charging handle into the channel located within the upper
- Take the bolt carrier group, and align the gas key with the channel that is located inside the charging handle
- Eventually, the bolt carrier group will lock in position and you should hear an audible click
- Assemble the upper and the lower receiver together
- Confirm that your bolt carrier works by pulling back the charging handle multiple times
- If the charging handle works, you can conduct a live test
Push the entire bolt carrier group forward towards the receiver
Suggested read: Our guide on the best AR-10 barrel recommendations. Definitely worth checking out if you are starting a new build.
Buyer’s Guide For The Best AR-10 Bolt Carrier Groups
These are the most important factors to consider when looking for a new bolt carrier group for your AR-10:
First and foremost, your bolt carrier group should come MPI tested, or magnetic particle inspected tested. This means that the bolt carrier group has been inserted into a magnetic field and covered in a liquid solution of magnetic particles. This process reveals any fissures, cracks, or other imperfections in the steel that the naked eye cannot detect on its own.
As a result, any bolt carrier group that comes with MPI testing should be durable and safe to use over the long term. At the very least, a bolt carrier group with MPI testing should be able to last tens of thousands of rounds over many years without issues.
HPT, or high pressure testing, means that the bolt carrier group is capable of firing high pressure cartridges rated above SAAMI specifications. If the bolt carrier group is able to handle these kinds of higher pressure rounds without issues, it means that it is also capable of handling normal cartridges without issue as well.
A drop-in design for a bolt carrier group means that the services of a gunsmith are not necessary to get it to fit into your AR-10. Ideally, no tools will be required to install your bolt carrier group into your AR-10 either.
A drop-in design also means that the entire bolt carrier group is already assembled and ready to go. Otherwise, you would need to assemble each of the components together yourself, which can be a major hassle.
Speaking of drop-ins, replacing your stock on an AR-10 is one of the easier modifications. Be sure to check out our guide on AR-10 stocks.
The 3 Best AR-10 Bolt Carrier Groups For 2020
Now that we’ve covered why you need to upgrade your bolt carrier group, here are our top three choices for a bolt carrier group for 2020:
JP Enterprises .308 AR Low Mass Bolt Carrier Group
The JP Enterprises .308 AR Low Mass Bolt Carrier Group is machined out of a very tough and corrosion resistant stainless steel. It’s designed to cool down fast after extended firing sessions, which is something that most other bolt carrier groups on the market cannot boast of.
But the real standout of the JP Enterprises is how lightweight it is. This BCG has a total weight of just under nine ounces, which should most likely reduce the weight in your existing AR-10. This is also surprising when you consider the stainless steel construction as well.
Extra bearing surfaces on the JP Enterprises help to reduce wear and improve the bolt alignment, the latter of which specifically translates to reduced recoil as well. Meanwhile, the stainless steel is coated in both Melonite QPQ and chromium nitride finishes, which makes this one of the most rust resistant and surface wear resistant bolt carrier groups that you can get for an AR-10.
All in all, the JP Enterprises .308 AR Low Mass Bolt Carrier Group represents a solid choice due to the fact that it is both lightweight and also highly durable thanks to its chromium nitride finish and Melonite QPQ finishes. It’s also a solid fit for rifles that come with tunable gas systems.
- Very lightweight at just nine ounces
- Bolt has a chromium nitride finish for superb rust resistance
- A perfect fit for rifles and carbines that come with tunable gas systems
- Coated in Melonite QPQ
- Built out of stainless steel
- It will create more recoil without an adjustable gas block
CMMG .308 Bolt Carrier Group
The CMMG .308 Bolt Carrier Group was designed specifically by BCG to be able to take on heavy duty applications such as tactical missions. As a result, this is one of the most solidly built bolt carrier groups that you can get, being built out of 8620 steel with a chrome lined interior. Meanwhile, the extractor has been constructed out of S7 tool steel.
Every component is coated in phosphate, which while rather crude looking and resembling of Parkerizing, is also very rust and corrosion resistant. Phosphate finishes are commonly used on military firearms and equipment due to the fact that it does a good job of protecting the surface from rusting while also being cheap to apply. However, the use of phosphate also means that it may be a little bit rough to use at first, and you’ll need to fire a few magazines through your AR-10 to break it in properly.
Overall, the CMMG .308 Bolt Carrier Group is a decent option due to its durable 8620 steel construction combined with the very durable and rust resistant phosphate finish. CMMG also designed this bolt carrier group specifically to function well with the .308 and 7.62x51mm NATO rounds.
- Has a phosphate finish for good rust and corrosion resistance
- Built out of durable 8620 steel
- Optimized for the .308 Winchester round
- Rough out of the box and will require a good break-in period to smooth it out
Brownells .308 AR Bolt Carrier Group
Don’t let the name of the Brownells .308 AR Bolt Carrier Group. In addition to .308, this bolt carrier group is also compatible with just about every other caliber that the AR-10 is made for, including 6.5 Creedmoor, .260 Remington, .338 Federal, .243 Winchester, and 7mm.
This BCG is built out of a very tough and durable 9310 steel. It’s been both shot peened and heat treated to boost durability as much as possible. The gas key screws have been staked and torque, and the extractor has a rubber insert and spring. The surface to this BCG is coated in a black nitride finish that is very resistant to rust and surface wear.
Take note that this bolt carrier group is designed to function well with DPMS style rifles and is not compatible with Armalite style rifles.
The Brownells .308 AR Bolt Carrier Group is designed by Brownells to function with nearly very caliber the AR-10 is made for. It’s built out of a very tough 8620 steel with a black nitride finish that resists both rust and surface wear very well.
- Designed to function properly with many different calibers
- Has a black nitride finish that is very resistant to rust and surface wear
- Built out of hardened 9310 steel
- Compatible with DPMS-style rifles
- Not hard chromed on the inside
- Not compatible with Armalite-style rifles
And that concludes our list of the top three best bolt carrier groups for an AR-10 in 2020.
The bolt carrier group is one of the most vital components to ensure that your AR-10 will function properly. Any one of the three bolt carrier groups that we have taken a look at today should be a good option for your AR-10, or alternatively, you can go with any other bolt carrier group available on the market that meets the criteria that we outlined in the buyer’s guide section.