While every part of any AR-10 build is important to the gun’s overall performance, one of the most important parts is the bolt carrier group (BCG). Why?
Well, the BCG is the part of the AR-10 that is responsible for making semi-automatic fire possible. If that isn’t important in an AR-10 then what is?
Check out the best AR-10 BCG options on the market today below.
At a Glance: Our Top Picks for AR-10 BCG
- OUR TOP PICK: J P ENTERPRISES - 308 AR Low Mass Bolt Carrier Group
Comparison of the Best BCGs For the AR-10 .308
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What to Watch For When Buying a BCG for an AR-10
Considering the importance of the BCG to proper and reliable AR-10 operation, you’ll want to be as knowledgeable as possible about them when shopping for one. Keep the following information in mind to help ensure you find the best BCG for your AR-10.
This Section Written By:
Brian Belko
Expert Author
Brian is an experienced freelance writer and technical writer who has previously written for publications such as Wide Open Spaces, Bigfoot Gun Belts, Alien Gear Holsters, and Kampgrounds of America. He brings both a passion for writing and a love of the outdoors to his published content.
Aside from writing and the outdoors, Brian enjoys gardening, being a co-host on The Nostalgia Blast Podcast, and learning to code.
Well Tested, Shooter Approved
Manufacturing quality is one of the most important things to keep in mind when it comes to bolt carrier groups. While most of the known and reputable brands won’t have major problems with manufacturing quality, there are still a few things shooters can look for to make sure the BCG they choose is ready for reliable action. Magnetic particle inspected (MPI) and High pressure testing (HPT) are two things that shooters should check to make sure their chosen BCG has.
MPI is a test that places the BCG in a magnetic field and then covers it in a magnetic liquid solution. This test will expose any imperfections that might be present in the BCG including fissures and cracks. A BCG that has passed MPI will be safe to use and durable for thousands and thousands of rounds.
High pressure testing is pretty self-explanatory. It tests the BCG at pressures that exceed SAAMI specs. If it can handle those pressures, factory-loaded ammunition won’t be an issue. A successful HPT test is also an important thing for reloaders to look for in a BCG.
Photo credit: gfycat.com
Put on a Coat
As you read descriptions of all the different bolt carrier groups, you will see a variety of different finishes being offered. There isn’t really a wrong option among them, but they do each have their own pros and cons. For most shooters, the main difference will come down to price, but a change in performance isn’t likely to be noticed.
There are finishes such as phosphate and black nitride on the lower end, which both have high durability and corrosion resistance with phosphate being mil-spec and nitride requiring less lubricant for proper operation. On the higher end finish such as diamond-like carbon and titanium nitride which offer very smooth operation and long-lasting durability but are more expensive.
Your choice will likely come down to what you want to spend and on the color of each finish option and how well it goes with your desired rifle aesthetic.
Covering Your Bases
Choosing a bolt carrier group for your AR-10 is an important decision that deserves some time and research to make correctly. In other words, do your due diligence before deciding on one. Read reviews, familiarize yourself with the terminology, check out some videos and forum discussions, and look for information on which BCGs are best for your specific type of rifle. At the end of the day, you’ll be thankful you did.
Reviews of the Best AR-10 BCGs
Now we’re going to transition into the review section of our article and take a look at a few products that made our list. For each BCG, we’re going to discuss their main features and examine their pros and cons. Let’s get started!
Best Overall .308 AR-10 BCG:
J P Enterprises - .308 AR Low Mass Bolt Carrier Group
Pros
Cons
What Recent Buyers Report
A lot of new users were happy with the overall functionality of the BCG. One of the benefits that really made this a hit with users was the ability to reduce a good amount of felt recoil. A lot of users said that installing this BCG on their AR-10 reduced recoil by quite a bit. One user even said that he noticed his shots being a bit more accurate than usual after installing this BCG due to feeling a little less recoil.
Why it Stands Out to Us
This BCG is machined from extremely durable stainless steel. It’s proven itself to be physically tough and easy to install for the purpose of a better functioning AR-10 rifle. Best of all, it makes using your AR-10 more enjoyable. Of course, let’s not forget the BCG’s ability to keep the rifle cool in extended periods of shooting. If you’re spending a few hours at the range and hate the idea of having an overheated rifle, then this BCG could be one of the building blocks to ensure that your rifle remains cool for the most part, even after a long day of use.
JP is one of the first AR-parts manufacturers starting to produce lightweight BCG models. The JP Low Mass bolt carrier assembly is made from SAE 9310 stainless steel and treated with chromium nitride. Considering this unit is made of steel, it owes its low mass to reduced-weight cuts without sacrificing strength.
The JP lightweight carrier comes with extra bearing surfaces to enhance bolt alignment, reduce wear and allows for a lighter recoil impulse. The customers who buy this model need to keep in mind that lightweight bolt carriers have significantly lower reciprocating mass than standard Mil-Spec carriers and need to be used with an adjustable gas block for less gas flow and softer recoil.
You will notice that forward assist serrations are not included on JP Low mass carrier, but since this model is only used in rifles that are meant for competitions, this feature will not be missed.
Who Will Use This Most
This would be a great BCG for those who want to extend the longevity of their rifles. Heat can shorten that if it consistently gets hot with each and every use. Heat can even slowly eat away at the rifle’s overall performance. So if you need an accessory to keep that to a minimum, then this BCG is a good place to start.
Bottom Line
The JP Enterprises .308 Low Mass Bolt Carrier Group is focused on making sure your rifle stays cool and remains as functional as possible for as long as you use it. Don't let consistent overheating get the best of your AR-10 rifle. You'll want it to last long and function the same way as if you're firing it for the first time. If you want superior durability and heat dissipation that is hard to rival, this BCG might just be the kind that will fit your needs.
When used with other JP hardware, this BCG works like a Swiss watch, making an impression of firing more like a .22 than a centerfire rifle.
The JP, low-mass BCG is designed to upgrade any JP or DPMS or Remington AR-style .308 rifle (LR-308 pattern only), especially if you plan to shoot competition or heavy use.
Best Overall 5.56 AR-10 BCG:
Brownells - M16 5.56 Lightweight Bolt Carrier Group
Pros
Cons
What Recent Buyers Report
Most of the new buyers said that this BCG was super tough and built like a tank. Furthermore, they managed to install this without the aid of a gunsmith in as little as a half-hour or less. Once installed, they managed to utilize their rifles to their advantage. Most of the users of this BCG in particular were hunters, target shooters, and even those who are in tactical situations. Overall, they were happy with the durability and overall recoil reduction.
Why it Stands Out to Us
Made from high-quality tool steel, this BCG is without a doubt one of the most durable available on the market. So, it won’t get damaged or scuffed up no matter how many times you throw it around. Don’t believe us? When you get this BCG just give it a shot. Find a wall and throw this at it. It will work just fine without a scratch. Apart from the durability, it’s also able to reduce a good amount of recoil. So if you want something that will allow you to gain complete control over your rifle, you should consider getting a BCG as part of your rifle upgrade.
With the release of its new lightweight bolt carrier, Brownells has joined the trend of low mass BCGs purpose-built for AR-15 competitors. While the heavy-duty bolt itself is a standard model using 9310-tool steel, the bolt carrier is machined from hardened 8620 steel and lightened by cutting out the material, leaving just enough to make it functional.
The Brownells M16 Lightweight BCG comes fully assembled with a properly torqued and staked gas key, and features the necessary black insert and O-ring around the extractor. Unlike some other lightweight BCGs, the Brownell has retained the forward assist notches.
All components are magnetic particle inspected (MPI) and after machining they are heat-treated and shot peened to ensure quality and reliability. This lightweight bolt carrier group comes in three flavors of black nitride, titanium nitride (TiN), or nickel boron finishes.
Who Will Use This Most
This would be a great BCG for those who use their AR-10 for almost any reasonable purpose. It’s tough, it’s reliable, and it will certainly keep your rifle cool should you use it for extended shooting periods. Add this to your rifle and you won’t regret a thing after using it for whatever purpose that is deemed necessary.
Bottom Line
The Brownells M16 5.56 Lightweight Bolt Carrier Group is the closest thing you can get to a factory replacement. It will really give your rifle more of a boost compared to factory defaults, which have a higher chance of failing you even after short term use. You certainly don’t want to deal with that down the road.
The Brownells BCG is compatible with 5.56x45 NATO, .223 Rem., .300 Blackout, and .204 Ruger calibers. At a weight of only 8.2 ounces, this low mass assembly is light enough to decrease the overall weight of a lightweight AR build and reduce the felt recoil of any AR-style firearm.
3. DPMS - .308 AR Bolt Carrier Group
Pros
Cons
What Recent Buyers Report
A lot of recent buyers were very happy with this bolt carrier group. They said that it was easy to install and was super durable and lightweight, thus not adding any additional weight to the rifle itself. One user even said that the headspace on this BCG was perfect and allowed for a really good fit. He added that it also allowed for superb, reliable functioning that he was long looking for in a real BCG.
Why it Stands Out to Us
This bolt carrier group is absolutely perfect for the purpose of making your AR-10 function quite well in any given situation. You might be a hunter or a target shooter, but you want a fully functioning AR-10 rifle that will get the job done and make it really enjoyable to shoot time and time again. If you’re building a rifle from the ground up, you’ll need a BCG to include in your installation. Without it, obviously, the rifle would be useless.
DPMS 308 AR Bolt Carrier Groups remains the most common .308 BCG’s available groups that dominate the .308 AR rifle platform. DPMS LR-308, a shot peened bolt, is machined of Carpenter 158 steel alloy and carrier of 8620 carbon steel. The carrier is chrome lined and available with either a mil-spec phosphate coating or hard chrome finish.
The complete AR-style .308 bolt and carrier comes with gas key installed and staked. DPMS assembly consists of the bolt carrier, the gas key, the gas rings, the bolt assembly, the ejector, the extractor, the cam pin, the retaining pin, and the firing pin.
The most frequent customer complaints refer to finish with noticeable traces of machining process and very tight fit between the BCGs and uppers, which prevents cycling.
Who Will Use This Most
This BCG would be an exceptional accessory for so many AR-10 users. It is solid in quality, allows for excellent functionality, and makes the rifle a lot more reliable in many situations. If you want an AR-10 to work the way you want it to, it starts with the accessory that is considered the “heart” of the rifle. It’s easy to install and really sturdy in quality. What more can you ask for in a BCG?
Bottom Line
The DPMS .308 AR Bolt Carrier Group is solid and will definitely get your AR-10 in working order. Just install this bad boy in your rifle and it will run smooth like a well-oiled machine. You can certainly make it last it a long time, so long as you take the best care of it.
This genuine factory replacement is the closest unit we have to a “standard”. The eye-catching difference is the absence of Forward Assist serrations since the forward assist engages a shoulder on the carrier still forcing the bolt forward when needed.
4. Bravo Company - M16 5.56 Bolt Carrier Group
Pros
Cons
What Recent Buyers Report
As expected, many new users pointed to this BCG's ability to stay cool while they were using their rifles for extended periods of shooting (i.e. target shooting). They said that once it was installed, they were able to test it out at the range for a few hours of continuous shooting. Afterward, the amount of heat dissipation was increased.
Why it Stands Out to Us
This BCG is perhaps one of the toughest on the planet. And it’s the one BCG that has been battle-tested for all the hardcore uses it can face before they even hit the shelves for sale. It’s been heat-treated, peen tested, and has passed many quality and reliability tests with flying colors. So if you want a BCG that you know won’t steer you wrong in terms of quality and reliability, this is the kind of accessory that will give your AR-10 more functionality compared to those subpar factory default BCGs.
Undoubtedly, the Bravo Company Manufacturing (BCM) M16 5.56 BCG is one of the best selling and most popular AR-15 bolt carrier groups. Without unnecessary exotic coatings or any other less proven gimmicks, it entirely satisfies different necessities and shooting styles.
Bravo Company is offering a fully assembled Bolt Carrier Group with a parkerized exterior. The carrier and gas key has a chrome-lined interior, the bolt assembly is made from the Mil-Spec Carpenter No. 158 steel, and the extractor spring is made of tool steel.
As a standard, the BCM BCGs are staked with grade 8 hardened fasteners, particle tested (MPI), and heat-treated (HPT) for more durability.
Following machining, the bolt is shot peened for increased strength and high heat resistance. Furthermore, each unit is thoroughly test fired for function before being shipped, so chances are you might spot handling marks on them as well.
Who Will Use This Most
This is another BCG that can be used for the sake of general purposes. If you hate your factory default BCG and want to make an upgrade, this is your opportunity to do so with this BCG. Once you’ve installed it, you’ll be feeling immediate changes to the rifle and you’ll swear that you’ll double-check and make sure that the rifle you’re firing is actually your own.
Bottom Line
The Bravo Company brand is known for making some pretty solid accessories, and this BCG is no different. You’ll definitely want to give this bad boy a try if you want your AR-10 to last you a dang good long time and provide you with excellent reliability that is hard to match.
Although Bravo unit is primarily built for first service semi-automatic rifles, this BCG features full auto profile, which means it is compatible with fully automatic rifles too. Knowing that the US Navy, US Marines, and the SOCOM are on the Bravo list of clients, you can be assured this product would make a great addition to your AR-10.
5. CMMG - .308 AR Bolt Carrier Group
Pros
Cons
What Recent Buyers Report
A lot of new users were looking for a BCG that was designed to take on heavy-duty applications like target shooting and tactical use. They were not disappointed with this BCG at all. The installation was quite simple and straightforward and it made their rifles a lot more fun to use. One user even said that the BCG is quite tough and lightweight; he expects it to last him a long period of time.
Why it Stands Out to Us
This BCG is hands-down one of the most solidly built BCGs on the market. This was made for the hardcore stuff. So if you use your AR-10 in tactical situations or for longer periods of target shooting, this just might be the kind of BCG you’ll want to invest in. For the high quality and ease of installation, buying this puppy is worth every penny. If it seems too expensive, don’t fret. There are all kinds of BCGs that are excellent in quality and priced affordably.
Complete CMMG's bolt carrier assembly includes bolt, bolt carrier with the adequately staked gas key, cam pin, stainless steel firing pin, and retaining pin. The CMMG bolt is built from 9310 steel, the carrier is machined from 8620 steel with the chrome lined interior, while the extractor is made of hardened S7 tool steel.
All components feature a durable, Phosphate matte black finish. Both bolt and bolt carrier are Magnetic Particle tested and Shot Peened. Like some other counterparts, CMMG BCG comes without serrations for a forward assist.
Who Will Use This Most
This will be a great BCG for those who have been able to use their AR-10 rifles for the purpose of high-stress situations. So if you are in law enforcement or the military, or if you are a shooter that likes to spend all day shooting up targets at the range, this is the BCG that should be at the top of your list of potential choices. Just because it’s lightweight and durable doesn’t mean that it’s weak by any stretch of the imagination.
Bottom Line
The CMMG AR Bolt Carrier is hardcore and will definitely handle all your AR-10 functionality needs after install. You’d be hard-pressed to find something that is this excellent in strength and reliability anywhere else. Plus, it’s built for the heavy-duty applications so you can expect this to last you quite a while.
The bolt/carrier group from CMMG is ready to drop into your .308 rifle based on LR308 Platform. Although it does not have the smooth fitting feel of other bolt assemblies, it’s made under the standard that is most widely used for bolt carrier groups.
6. WMD Guns - M16 5.56 Nickel-Boron Bolt Carrier Group
Pros
Cons
What Recent Buyers Report
Many new users had nothing but great things to say about this BCG’s durability. They said that it was lightweight, tough as a tank, and would definitely be best for tactical and hunting applications. The install was easy and didn’t require any advanced gunsmithing skills. But using it did require a willingness to have fun firing off an AR-10. And fun they did have after installing this and discovering that it also reduced a good chunk of recoil.
Why it Stands Out to Us
Made from a mix of nickel and boron, this BCG looks good. But it wasn’t made to look pretty. It was made to kick butts and take names. Its toughness is proven to handle the heavy-duty usage of an AR-10, so if you want something that won’t fail on you after firing many rounds, then you’re really going to love this BCG. It’s what makes an AR-10 work (literally). So why not use something that will go the distance in terms of longevity? Who knows, this will probably still be good as new after a few years of consistent use.
WMD Guns is a leader in coating technologies, and their BCG with proprietary NiB-X nickel boron coating will allow extremely extended periods between cleaning cycles. By supporting traditional form, this BCG features full forward assist teeth, a properly staked gas key, an M-16 cut, and a classic profile.
The WMD assembly utilizes the massive M16 Full Auto carrier, which will function in any semi-automatic AR-15 rifle. The carrier body is constructed of case hardened 8620 and its hardened extractor features next-generation NiB-X Nickel Boron coating, which offers 40% greater wear life than Mil-Spec coating.
The bolt is machined from heat treated (HPT)158 Carpenter steel, and is shot peened and magnetic particle inspected (MPI). Additionally, the WMD Nickel Boron BCG is available in the semi and fully automatic models, with or without a hammer certified per Government drawings.
Who Will Use This Most
This BCG will be great for tactical and even competitive shooting users. These are two applications where consistent long-term use is probable. You want something that will be tough and can handle longer periods of shooting. Not to mention, you want a BCG that is, in a word, indestructible. If that’s what you want in a BCG, you got it with this one.
Bottom Line
The WMD Guns M16 Nickel-Boron Bolt Carrier Group will definitely stand out as the go-to choice for most AR-10 users that are constantly using their rifles. The last thing you want is a BCG to fail you all of a sudden after short-term use. This BCG in particular will go long and last many years or decades. This just might be the last BCG you’ll ever purchase for quite a while.
All in all, the WMD Bolt Carrier Group offers a cutting-edge coating for high-volume shooters or anyone who will use it in dirty and sandy environments. With minimal or no lubrication, this durable and low maintenance bolt carrier group will make your investment last longer and function smoothly.
What is the Bolt Carrier Group (BCG) and How Does it Work?
Nowadays, firing systems demand more complex and sophisticated bolt units. In AR-15’s, the bolt and its carrier are a primary functioning part, a lifeline of your rifle, and the part that moves the most. In other words, the heart of AR platform rifles is the Bolt Carrier Group, or BCG for short.
It’s full of moving parts; more precisely, it consists of 6 main components: retaining pin, bolt cam pin, gas key, bolt assembly, carrier, and firing pin. In total, seventeen parts comprise the bolt carrier group.
With all AR-15/AR-10s and other AR-style guns, the BCG is located between the upper and lower receiver; while enduring extreme temperatures and pressures it reliably performs three functions -- cycling, ejection, and reloading. Essentially, the BCG has to fire a cartridge, load a new one, and expel the empty case, all by itself.
What to Look For When Buying a BCG
Until recently, aftermarket parts offered for AR-15 parts and accessories was dominant, but today, the situation is completely changed because of the sheer volume of companies offering AR .308 parts.
Type of BCG
There are many different types of BCGs, all with many different characteristics. If you are looking for the best AR-10 BCG, you will need to be familiar with phrases like Full-Auto Bolt Carrier Group, or the variety of material types, and acronyms like HPT and MPI.
Therefore, we will try to decrypt that strange language of bolt carrier groups and make an effort to clarify one of the most confusing aspects in AR world, improving a .308 Bolt Carrier Group.
Photo credit: arbuildjunkie.com
Since there is no mil-spec standard in .308-bolt carrier group, as you have likely seen in the AR-15 family, the first thing to know is that there are a multiple incompatible .308-bolt carrier group designs. According to this, you can only use an AR-10 BCG in an Armalite AR-10 Rifle, and DPMS LR-308 BCG in .308 rifles based on the DPMS .308 platform.
However, there are several other designs, but these two are the most common in the hardware section called .308 Bolt Carrier Group. Along with these limitations, it is not recommended to use one BCG in more than one rifle, since the bolt and barrel extension contacting surfaces wear together during exploitation, making themselves unique.
In general, there are two common BCG profiles: semi-auto and full-auto. Although the choice of "semi-auto" or “full-auto” (SA or FA) refers to the intended use of the bolt carrier group, an FA or M16 style BCG is more in demand due to its versatility and shrouded firing pin.
The shrouded pin ensures the carrier can take the force and apply it evenly to the hammer after every round. By contrast, an unshrouded firing pin triggers excessive wear on both the hammer and firing pin, which can easily break your firing pin with hard use.
The difference is in the bolt's carrier itself, as a full auto carrier has a little more material on the back compared to semi-auto BCGs.
As previously mentioned, semi-auto (SA) carriers weigh less than FA carriers. Also, due to the cutback at the rear portion, semi-auto carriers can use a lighter buffer, which results in even more weight savings if you’re building your own AR-10 style rifle.
BCG Full-Auto vs Semi-Auto
Besides that, the low mass of semi-auto bolt carrier groups has their benefits, such as minor recoil and somewhat increased rate of fire.
On another note, the full auto (FA) BCG has more weight than stock AR-15 BCG and offers more consistent reliability and function in your rifle due to the greater mass.
Material
Another feature to look to is the material of BCG. Because the BCG faces a lot of heat and stress, it should be perfectly machined to deliver optimum performance. Good old-fashioned steel is the classic choice for the construction of this piece of metal that slides back and forth with each shot.
The most common steels for manufacturing BCGs are Carpenter 158 and 9310 steel used for the bolt, while the carrier is built from 8620 steel. However, the BCGs made of aluminum, titanium, and hybrid mixture of those three elements are also available on the market.
Finish
Besides flawlessly machined bolts and other parts, the finish of BCG is a critical feature. Practically, the coating of the bolt carrier group affects its ability to resist heat and corrosion, and also determines how it will operate.
There are a multitude of finishes, but for most builds, a Mil-Spec, phosphate coated BCG is the standard. It offers an economical, durable, and highly corrosion resistant exterior. Since the surface is more porous, it is quite susceptible to fouling and a bit challenging to clean.
For years, a hard chrome finish was an excellent alternative, but it has lost some popularity with the rise of newer coating technologies.
While the manganese phosphate coating is the standard finish on most “regular” BCGs, the newer coatings generally are more durable, require less lube to run smoothly, and they often cost 2 or 3 times the price of phosphate coated BCG.
According to Mil-Spec requirements, the interior of the bolt carrier and the gas key must be chrome-lined to provide a smoother and corrosion resistant surface on the inside.
Assuming that every quality made BCG has undergone heat treatment, it should also be treated through shot peening process. This involves tiny spheres known as "shot", which are blasted at the bolt to relieve stress from the metal.
How to Install BCG on an AR-10
After dropping down the charging handle into the channel inside the upper, then take the BCG with a bolt in its most outwards position and align the gas key with the channel inside the charging handle.
Next, push the complete bolt assembly towards the receiver until it locks into position.
Finally, assemble the upper and the lower receiver, push in the takedown pins, and your rifle is now complete.
Pull your charging handle several times to check if your AR-10 is working correctly; if everything is okay, you are ready for a live test. As with the most of AR parts, it is possible to purchase the components individually or obtain an entire pre-assembled bolt carrier group unit.
For first time buyers and fresh AR-builders, it’s more reasonable to start with complete BCG from a renowned manufacturer as this decision will profoundly improve your chances of buying the right Bolt Carrier Group.
Conclusion
Besides the barrel, the bolt carrier group is often considered the heart of an AR-rifle. Because of the diversified choices on the market, purchasing the best AR-10 BCG can be a confusing task. While there are BCGs that are professional and general at the same time, there are also specialized units like lightweight bolt carrier groups intended to make top performing results at competitions and ranges.
Above all, you should know that most issues with AR's have to do with the BCG, so if you make a wrong selection, your firing experience will be a lot less enjoyable. On the other hand, by selecting the right bolt carrier group for your needs, you will get the best performance out of your AR-10.
