Best AR-15 BCG’S – Upgrading The Bolt Carrier Group

by Travis Pike

August 23, 2022



The AR-15 is a fairly simple rifle. That’s why someone with no technical skills and gunsmithing knowledge can build one fairly easily. Although having some skills, Youtube, and the right tools helps.

Its simplicity led to modularity, and its modularity has propelled it into a stratosphere of popularity. Every little thing about the AR-15 can be swapped, changed, upgraded, and more. One of the more interesting upgrades you can make is swapping the bolt carrier group. 

The AR-15 bolt carrier group is the heart of the weapon. It contains the parts necessary to ensure proper and reliable function. It’s called a carrier group because it’s a group of parts. This includes the bolt, which has the extractor and ejector. At the top sits a gas key which acts as what’s essentially a piston to drive the BCG rearwards. 

The design is simple, and you wouldn’t think you’d see a lot of different designs. Well, here we are! We have a list full of the best BCGs on the market that will cover the most popular uses and needs for an AR-15 rifle, pistol, or SBR.

Best AR-15 BCG’s

Bravo Company BCG
  • Strict MIL-SPEC Design
  • HPT/MPI Tested and inspected
  • Perfect for Maximum Reliability
Check Price
JP Enterprises LMOS
  • Low Mass Carrier
  • Designed for Multiple AR Calibers
  • Available as Complete BCG
Check Price
PSA Gen4 9mm BCG
  • Pistol Caliber Carbine Bolt
  • Hybrid Design For Multiple Magazine Patterns
  • Designed For Blowback ARs
Check Price
SilencerCo Enhanced BCG
  • Designed for Enhanced Reliability When Suppressed
  • A mix of MIL-SPEC and Enhanced Design
  • Works Well with SBRs/Pistols
Check Price
Bootleg Four Position BCG
  • Adjustable BCG
  • Uses S7 Tool Steel 
  • 5.56 Only
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Brownells Titanium BCG
  • Lightweight Design
  • Multi Caliber
  • DLC Coating
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Geissele Enhanced AR-15 Bolt Carrier Group
  • Full Mass
  • Beyond MIL-SPEC
  • Nano Coating
Check Price

Best AR-15 BCGs

  1. Bravo Company BCG
  2. JP Enterprises LMOS 
  3. PSA Gen4 9mm BCG
  4. SilencerCo Enhanced BCG
  5. Bootleg Four Position BCG
  6. Brownells Titanium BCG
  7. Geissele Enhanced AR-15 Bolt Carrier Group

Best AR-15 BCGs Specifications

Below is a list of our Best AR-15 BCGs. Here we can compare and line up the specs from each of the products and help you make the best decision possible.

Bolt Carrier GroupMaterialFinishType
Bravo Company BCG158 Carpenter SteelPhosphateFull Auto
JP Enterprises LMOSStainless SteelStainlessLow Mass
PSA Gen4 9mm BCG8620 SteelNitrideBlowback PCC
SilencerCo Enhanced BCG8620 SteelBlack NitrideFull Auto
Bootleg Four Position BCGS7 Tool SteelLithium Isonite CoatingAdjustable
Brownells Titanium BCGTitaniumDLCFull Auto
Geissele Enhanced AR-15 Bolt Carrier Group158+ Carpenter SteelNanoweaponFull Auto

Best AR-15 BCG’s Reviews

Now we’ve had an overview look at our list, so let’s take time to individually review each BCG. In this section we’ll be revisiting our specs, speaking about the product, and looking at the pros and cons.

Bravo Company BCG Specs

  • Materials 158 Carpenter Steel
  • Finish Phosphate
  • Type Full Auto

Bravo Company BCG Review

If you need or even just want a rock solid, MIL-SPEC BCG, then Bravo Company Manufacturing has you covered. Is it fancy? No. Is it packed full of advanced features? No. Is it reliable, well-made, durable, and proven? Hell to the yeah. Bravo chases QC like a lion chases a gazelle. They are on top of it and produce top-tier products, and their BCG is no different. BCMs blems are better than some companies’ production products. This BCG strictly adheres to tradition and, along the way, makes a great BCG. 

 If you are an AR aficionado, then the construction of the BCM BCG won’t surprise you. It’s made from MIL-SPEC Carpenter No. 158 steel and shot peened for increased strength. BCM takes the extractor and ejector and uses machine tool steel for total durability. It’s extremely strong and will suffer the concussion and power of tens of thousands of rounds without complaint.

The Bravo BCG uses USGI, American-made, grade 8 fasteners to secure the gas key, and its’ properly staked for increased durability. The gas key is chrome lined and heat treated to take all the abuse that a 5.56 round tosses at it. Predictably BCM high-pressure tests and uses magnetic particle inspection to ensure the BCG is well made and flaw free. 

It’s not fancy or high-tech, but it’s a rock-solid choice if you want to keep reliability high and stick to the standard AR 15 layout. 

Bravo Company BCG Pros and Cons

  • Well Made
  • Tested
  • High Levels of Quality Controls
  • None

Bravo Company BCG Deals

JP Enterprises LMOS Specs

  • Material Stainless Steel
  • Finish Stainless
  • Type Low Mass

JP Enterprises LMOS Review

JP Enterprises takes big risks with its rifles, components, and products. They are always experimenting and innovating with complete rifles and even their individual components. The JP Enterprises LMOS represents one of the more durable and better-made lightweight Bolt Carrier Groups. Lightweight BCGs can be a risk, but the LMOS ensures quality, durability, proper design, and even caliber compatibility. 

The LMOS weighs 8.8 ounces with the JP Enhanced Bolt and 6.68 ounces without it. The reduction of weight helps reduce recoil. First, less weight being thrown backward equals less force into your shoulder. Additionally, when paired with an adjustable gas block, you can reduce the gas being directed rearward to the minimum amount necessary to cycle the rifle. With a low-mass BCG, less gas is required for operation. 

The LMOS is made from stainless steel, and while its reduced mass, its durability isn’t an issue. Stainless steel is very strong and very durable. JP enterprises utilized increased bearing surfaces for slower wear and longer component life. The LMOS external stainless finish is easy to clean and cycles extremely smoothly. 

This low-mass carrier is well made and very durable. It won’t beat itself to death during a high round count day. If you are chasing recoil reduction, pairing the LMOS with an adjustable gas block will deliver the ultimate reduction second only to a compensator. Pair both together, and you’ll get something truly special. 

JP Enterprises LMOS Pros and Cons

  • Made in multiple AR 15 calibers
  • Low mass equals low recoil
  • Made to last
  • Expensive

JP Enterprises LMOS Deals

PSA Gen4 9mm BCG Specs

  • Material 8620 Steel
  • Finish Nitride
  • Type Blowback PCC

PSA Gen4 9mm BCG Review

Building a 9mm AR-15 isn’t as plug-and-play as building your typical 5.56 caliber carbine. You’ll have to choose various components to match all manner of choices you’ll need to make. One big choice will be what magazine patterns you are going with. The two most popular are Colt SMG and Glock mags, and once upon a time, those required different bolt carrier groups. 

PSA did away with that by producing their own hybrid style bolt carrier group that functions with both Glock and Colt SMG magazines. You can toss this sucker in your gun and use a variety of magazine options. If you have this bolt, you can use magazine adapters from Matador Arms or Endo without issue on top of Colt and Glock mags. 

The PSA Gen4 9mm, bolt carrier group is designed solely for blowback-operated pistol caliber carbines. You won’t be able to use this in a gas gun, piston gun, or anything other than a straight blowback gun. The BCG is made from 8620 steel, which is fairly standard and certainly won’t be challenged by a 9mm. 

The PSA BCG is made to function with the majority of AR 15 fire control groups, so you can very likely use your favorite trigger system. It’s not entirely compatible, though, and it’s wise to research which systems might not work with this BCG. If it’s standard MIL-SPEC fire components, then you’ll be good to go. If you want to eliminate the magazine compatibility issue of PCCs, then this is the route to take. 

PSA Gen4 9mm BCG Pros and Cons

  • Works With Various Magazine Patterns
  • Durable
  • Affordable
  • Doesn’t Work With All Fire Control Groups

PSA Gen4 9mm BCG Deals

SilencerCo Enhanced BCG Specs

  • Material 8620 Steel
  • Finish Black Nitride
  • Type Full Auto

SilencerCo Enhanced BCG Review

Why would a silencer company produce a bolt carrier group? This is speculation, but it’s likely because they recognized that a BCG designed for suppressed rifles would be quite handy. The SilencerCo Enhanced BCG mixes in MIL-SPEC parts where they can but also enhances the construction and design of the BCG to work better with modern suppressors. 

Suppressors increase back pressure and cause the gun to shoot more gas rearward into the receiver and sometimes in your face. (Check our AR-15 charging handles article for a way to fix this.) This gas brings back more dust, debris, and carbon into the receiver, making the BCGs dirtier, increases friction, and could cause failures. 

To help solve this problem, SilencerCo does several things. First, SilencerCo uses a black nitride finish. This is a smoother, slicker finish and helps the weapon function when filthy dirty. The black nitride finish is easier to clean and can quickly be wiped down with an oiled rag. SilencerCo also trimmed the BCG tactically to reduce the contact of the BCG with the upper, which reduces friction and increases reliability with a suppressor. 

SilencerCo also increased the mass of the BCG to work with the extra pressure being sent rearward. This ensures reliable function and improved extraction. SilencerCo went with case-hardened 8620 steel and used MIL-SPEC firing pins, extractor springs, and O-Rings. They also do a high-pressure test and use magnetic particle inspection to ensure the BCG is up to snuff.

SilencerCo Enhanced BCG Pros and Cons

  • Enhanced For Suppressor Use
  • Easy to Clean
  • Tested for Total Reliability
  • Doesn’t Excel without a suppressor

SilencerCo Enhanced BCG Deals

Bootleg Four Position BCG Specs

  • Material S7 Tool Steel
  • Finish Lithium Isonite Coating
  • Type Adjustable

Bootleg Four Position BCG Review

Adjustable stocks, adjustable pistol grips, adjustable charging handles, adjustable gas blocks, and now adjustable bolt carrier groups. The Bootleg Four Position BCG is the first time I’ve ever seen an adjustable BCG, and it’s one of the more interesting designs on the market. The Bootleg BCG has a four-position adjustment screw that is an ingenious design. On top of that, the BCG is made from high-end steel, and it uses a very modern coating. This might be the most high-tech BCG on the market. 

What’s the point of an adjustable BCG? Much like an adjustable gas block, an adjustable BCG allows you to tune the bolt to different levels of gas in different situations. The four settings of the Bootleg BCG allow you to tune the BCG to vent gas when used with a suppressor or even a short-barreled rifle. If you remove the suppressor, you can easily adjust the BCG back to normal to ensure reliable function. 

Shooters can adjust the Bootleg BCG through the ejection port and never have to remove the bolt from the gun. Bootleg also used a number of MIL-SPEC components and build designs. This includes a staked MIL-SPEC gas key which is often a weak point on BCGs. S7 steel is incredibly durable and will take tons of abuse, especially if fired suppressed in a select fire gun. It’s a tough-to-beat option if you don’t mind spending the money. 

Bootleg Four Position BCG Pros and Cons

  • Adjustable
  • Extremely Durable
  • Perfect for Suppressed Guns
  • 5.56 Only

Bootleg Four Position BCG Deals

Brownells Titanium BCG Specs

  • Material Titanium
  • Finish DLC
  • Type Full Auto

Brownells Titanium BCG Review

Titanium isn’t a cheap metal. It’s extremely strong while remaining lightweight. A titanium bolt carrier group allows you to trim weight without worrying about a weak BCG. Some BCGs are basically consumable items that are solely intended for competition use because their reduced mass typically equals reduced durability. With a titanium BCG, this isn’t a concern. 

Brownells got into the BCG game and began producing a relatively affordable titanium BCG. It’s not cheap but is much cheaper than most titanium BCGs. The Brownells Titanium BCG is constructed to extreme standards, and Brownells wasn’t interested in losing its reputation by building a crappy BCG. Brownells uses 6A1-4V titanium, and the bolt is made from 9310 tool steel. 

This type of bolt allows you to reduce recoil by reducing the mass slamming rearward and the amount of gas needed to operate the gun. The Brownell’s Titanium BCG pairs best with an adjustable gas block. At only 7.9 ounces, it’s fairly light and easy to tune your AR gas system around. 

This titanium BCG allows you to use multiple calibers, including 5.56, .300 Blackout, and .204 Ruger, without any issues. The bolt is also HPT and MP inspected. It’s a tough but lightweight option that won’t break the bank. 

Brownells Titanium BCG Pros and Cons

  • Lightweight
  • Multiple Calibers
  • Affordable (For Titanium)
  • Requires adjustable gas block to meet full potential

Brownells Titanium BCG Deals

Geissele Enhanced AR-15 BCG Specs

  • Material 158+ Carpenter Steel
  • Finish Nanoweapon
  • Type Full Auto

Geissele Enhanced AR-15 BCG Review

It’s crazy that Geissele started just making triggers and then slowly advanced into producing a little bit of everything. The Super Duty series set the current standard for AR-15 rifles. The Geissele Reliability Enhanced BCG tells just about everything you need to know within its name. The BCG is the core of the weapon’s operation and is very important to function, so making it as reliable as possible was Geissele’s goal. 

The Geissele Reliability Enhanced AR-15 bolt carrier group goes well beyond MIL-SPEC. It features 158 Carpenter steel, but not your dad’s 158 Carpenter steel. Geissele worked with Carpenter Steel metallurgists to produce a cleaner material with fewer impurities. They called Carpenter 158+. This material is stronger, more durable, and more consistent. 

Beyond the carrier, Geissele went and forged the bolt. A forged bolt promises to provide unbeatable durability and, therefore, reliability. Geissele applies a chrome-nitride finish to the BCG, and they call it Nanoweapon. This finish is strong and flake-free but also slick and allows the weapon to function with less lubricant. 

Geissele then does the standard testing we all know and love in our quality BCGs. This includes high-pressure testing and then magnetic particle inspection to ensure the BCG is ready for your worst day. 

Geissele Enhanced AR-15 BCG Pros and Cons

  • Extremely Durable
  • Slick Coating
  • Unbeatable Reliability
  • Expensive

Geissele Enhanced AR-15 BCG Deals

Best BCG’s – Buyers Guide

Before you leave this article, let’s talk about the world of bolt carrier groups. I’ve likely dropped some terminology you might not understand, and I want to make sure that it’s defined and explained. This section will help you learn a thing or two about bolt carrier groups in general, and you’ll leave here ready and equipped to pick your own bolt carrier group. 

Full Auto and Semi-Auto 

Oh boy, so you’ve likely heard the term Full Auto BCG a time or two in your research and in this article. Let’s explain what that means, but also, let’s clarify something. A full auto bolt carrier group does not convert your weapon to fully automatic. It’s just a standard for BCG construction. Way back when Colt decided that full auto bolt carriers might be an optics issue when selling the AR-15. 

Thus, they created the semi-auto BCG. If a semi-auto BCG is dropped into a full auto rifle, it will not allow for full auto or burst fire. The semi-auto BCG is slightly shorter and lacks the lug to press down on the sear release. Semi-auto BCGs seem fairly rare these days, and the world has kind of drifted away from them. 

Testing Procedures 

I’ve mentioned a few different tests most of our BCG manufacturers use to guarantee the quality of the BCG. These tests are high-pressure testing and magnetic particle inspection. These are tests required by the initial MIL-SPEC of the M16 BCG and are still important to this day. They help ensure you receive a high-quality and durable BCG free from weaknesses. 

High-Pressure Testing 

High-pressure testing is the use of a high-pressure test round that generates 70,000 PSI. A normal 5.56 round generates about 52,000 PSI. The purpose is to take the BCG to the limit and ensure it still functions. If it doesn’t break at 70,000 PSI, it will handle standard 5.56 without issue. 

Magnetic Particle inspection 

After you try to blow the BCG with your proof round, you conduct a magnetic particle inspection. This is a testing process that is really neat. A video on Youtube is interesting and worth watching to better understand it. Essentially they use a magnetic field and direct or indirect magnetization to detect flaws, including micro fissures and issues not possible to see with the human eye. 

Mass Matters 

Mass typically refers to the overall weight of a bolt carrier group. We have three different categories of mass, and the first is standard. This is the MIL-SPEC mass that is the most basic, high-functioning, reliability-guaranteeing design. It’s your standard BCG and is a full auto design. It works and has worked for decades now. 

The second most common is reduced mass or lightweight BCGs. These are designed to work in coordination with adjustable gas blocks. They allow a shooter to tune their rifle to their specific needs and ammunition to deliver a lighter recoiling rifle. These BCGs do tend to be less durable simply due to their designs, and you’ll often see metals like titanium used to reinforce the BCG. 

Finally, we have a relatively rare type of BCG, and that’s the increased mass. These are rare and are most commonly used with suppressed rifles. Suppressors create more powerful gas blowback, and the heavier bolt helps absorb that to reduce the violence of the action. This decreases recoil and helps increase reliability, and ensures proper extraction and ejection. 


What’s on the outside often counts just as much as what’s on the inside. At least when it comes to BCGs. The external coating can make a somewhat significant difference in the overall lifespan of the BCG. Let’s look at some of the more popular coatings out there. 

Phosphate – Phosphate is the military standard. It’s not fancy, but it works and has proven to be a reliable option for high-round count rifles. 

Nickel boron – Nickel Boron was all the rage a few years ago. It’s a shiny finish that works well with less lubricant, but that doesn’t mean you shouldn’t use lube. It’s a shiny finish that’s slick and very easy to clean. The downside is some poorly finished BCGs flake, and the finish gunks up your gun. 

TiN – TiN is titanium nitride. This is a much better version of nickel boron. It’s stronger but offers the same slicker nature and easy-to-clean design. It also comes in numerous very pretty colors. 

Nitride – Nitride is a black finish that’s ultra-strong and also has those same slick properties. It’s easy to clean and runs well with less lube than normal. Nitride is a great coating that’s both tough and affordable and also not so shiny. 

DLC – Diamond Like Coating is a very strong coating with a black-like finish. It’s ultra-strong and slicker than phosphate, but not the slickest finish. It’s still easy to clean, and its durability of it is tough to beat. 

Bolted on 

A good bolt carrier is a must-have. It’s absolutely essential in the cycle of operations for your rifle and ensures the gun runs and runs and runs. Plus, the BCG can most certainly be affected by external accessories, parts, pieces, and the like. If you like to tinker, then the BCG is a good place to start, especially if you want to take your rifle well outside the standard. 

What’s your favorite bolt carrier group? Let us know below! 


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About Travis Pike

Travis is a former United States Marine Corps Infantryman and currently a firearms writer, instructor, and works in Emergency Management.

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