Best AR-15 Bolt Carrier Group – BCG [2023]

What are the most important pieces in your AR-15? In my opinion the most important parts on an AR-15 are the barrel, BCG, and trigger. If you are looking to upgrade your existing rifle or looking at building a new AR-15, I would recommend spending the money and getting the best bolt carrier group you can.

When looking at BCGs the factors that are important to look at are testing procedures, full-auto vs. semi-auto rated, coating, materials, and weight. However, the most important factor for a BCG is reliability.

Your BCG is essential for the functionality of your firearm. So make sure that you purchase a BCG from a reputable company.

What is a bolt carrier group?

The BCG is a key piece of an AR-15. It is responsible for the proper functioning of the weapon and the cycling of the action. The BCG goes through the following cycle each time the gun is fired:

• Grab a round from the magazine and chamber it.
  
• Allow the hammer to strike the firing pin, which is located inside the BCG.
  
• The firing pin then strikes the primer on the chambered round, causing the round to fire and gas to travel down the barrel.
  
• The gas is then trapped by the gas block and sent back to the BCG and sent into the gas key.

• The built up gas pressure allows the BCG to grab and eject the spent shell casing from the fired round.

• The movement in the BCG re-cocks the hammer in the lower receiver for the next round.

• The movement forward grabs a new round from the magazine and chambers it.

What to look for when choosing a bolt carrier group.

Testing Procedures

There are two main testing procedures that are important when choosing a bolt carrier group.

Magnetic Particle Inspected (MPI)
MPI testing uses iron particles and magnetic charges to detect any flaws in the surface of the BCG. As they magnetize the BCG the iron particles are drawn to any imperfections. This means that a MPI tested BCG means that there are no surface imperfections.

High-Pressure Testing (HPT)
HPT is pretty straight forward. It subjects the BCG to high pressures to simulate the pressure felt from a live round.

Full-Auto vs. Semi-Auto

A BCG can be rated for either full-auto or semi-auto fire; however, purchasing a full-auto rated BCG is not the only piece needed for full-auto firing.

Full-auto and semi-auto BCGs operate the same, and have all the same parts. The only difference is the physical dimensions of the BCG, the full-auto BCG has a thicker portion in the rear. 

The extra thickness in rear of the BCG may add a little more weight but also gives it some durability.

Coating

Because the BCG uses gas to facilitate movement, there is a lot of carbon buildup that takes place. The coating on the BCG is designed to make the BCG harder, easier to clean, and give it a smoother cycle.

Some coatings provide actual value; however, there are some coating that provide no value but increase costs. Make sure that you do research on the coating to know if it is worth the extra cost.

Materials

Steel, aluminum, and titanium are the most common metals used for BCG construction. However, even within those categories there are multiple type of metals used.

The most important aspects of the different metals is durability, weight, heat resistance, and withstands wear and tear well.

Weight

In my opinion, the BCG is not the place to try to cut weight. For such an essential piece of your gun, the most important thing is reliability.

However, there are lightweight options, just make sure that they are durable, tested, and reliable.

What is the best AR-15 bolt carrier group?

Here are my top picks for the best bolt carrier group.

• Geissele Enhanced BCG (Editors Choice)
• Bravo Company Manufacturing BCG (Best Overall)
• Brownells Nitride BCG (Best Budget)
• Faxon 5.56 Gunner Lightweight (Best Lightweight)
• Daniel Defense Complete BCG (Best Alternative)
• Sharps SAGRS XPB (Best High End)
• WMD NiB X (Best Nickel Boron)

Geissele Enhanced BCG (Editors Choice)

Specs

Bolt Material : Carpenter 158+
Carrier Material : 8620 Steel
Coating : Nanoweapon
MPI & HPT : Yes
Full-Auto Rated : Yes

My Take

This is the most expensive option on this list. However, if there was ever a piece of equipment to spend a little more money it is the BCG.

The Geissele BCG is the best on the market in my opinion. It does come a high pricetag, but their “Nanoweapon” coating is one of the best coatings I have ever seen, and they use an enhanced Carpenter 158 steel for even more durability.

Bravo Company Manufacturing BCG (Best Overall)

Specs

Bolt Material : Carpenter 158
Carrier Material : 8620 Steel
Weight : 11.5 oz
Coating : Parkerized exterior and chrome lined inside carrier
MPI & HPT : Yes
Full-Auto Rated : Yes

My Take

The Bravo Company MFG BCG is the best bang for your buck BCG on the market. It has all the reliability and consistency of high end BCGs, at a fraction of the cost.

If you are thinking about getting a BCG for a new build or upgrading an existing build, I would budget a minimum of $200 for your BCG so you can get this BCG at a minimum.

Brownells Nitride BCG (Best Budget)

Specs

Bolt Material : 9310 Hardened Steel
Carrier Material : 8620 Steel
Coating : Nitride
MPI & HPT : Yes
Full-Auto Rated : Yes

My Take

If you really can’t afford a BCM BCG, the next best option is to get the Brownells Nitride BCG. It about half the price and is great for a new build.

However, if you purchased a complete upper receiver, I wouldn’t consider this BCG a “upgrade”. If you are wanting to upgrade an existing build, I would save up for a higher end BCG.

Faxon 5.56 Gunner Lightweight (Best Lightweight)

Specs

Bolt Material : 9310 Steel
Carrier Material : 8620 Steel
Weight : 8.5 oz
Coating : Nitride
MPI & HPT : MPI Only
Full-Auto Rated : Yes

My Take

As I stated earlier, I am not a big fan of lightweight BCGs. the extra 3 oz that you save on a BCG seems minimal compared to the structural integrity of a solid steel construction.

That being said, some people really like the look and feel of a lightweight BCG. It also cuts down on the recoil of the gun.

If you do go down the lightweight route, it is more important than ever to buy a BCG from a reputable manufacturer. No lightweight BCG is recommend more than Faxon, which is why I would start there.

Daniel Defense Complete BCG (Best Alternative)

Specs

Bolt Material : Carpenter 158
Carrier Material : 8620 Steel
Weight : 11 oz
Coating : Phosphate Chrome
MPI & HPT : Yes
Full-Auto Rated : Yes

My Take

Daniel Defense is known for making incredibly reliable uppers. The DDM4 is one of the most reliable rifles on the market. Reliability stems from focusing on the parts that matter.

The DD BCG is just that, reliable. Reliability is the most important factor in a BCG.

Sharps SAGRS XPB (Best High End)

Specs

Bolt Material : S7 Tool Steel
Carrier Material : S7 Tool Steel
Weight : 11.2 oz
Coating : DLC (Diamond-Like Carbon) Coating
MPI & HPT : Yes
Full-Auto Rated : Yes

My Take

Sharps is a new one for me. I only recently shot this BCG and really liked the design, feel, and coating of this BCG. I have been a long time Geissele over everything fan; however, my next build will most likely have a Sharps.

The only thing that I have heard (I did not experience this) negative about this BCG was the adjustable gas feature can throw off your rifle, especially when shooting suppressed.

The adjustable feature helps you manage recoil; however, too much adjustment can keep the BCG from cycling. So just beware of that.

WMD NiB X (Best Nickel Boron)

Specs

Bolt Material : Carpenter 158
Carrier Material : 8620 Steel
Weight : 11.7 oz
Coating :  NiB-X Nickel Boron
MPI & HPT : Yes
Full-Auto Rated : Yes

My Take

In my opinion the Nickel Boron coating is more of an aesthetic change than a functional one. All I have ever heard that the Nickel Boron coating is easier to clean and has a smoother finish than a traditional Nitride coating.

However, most high end BCGs are running proprietary coatings such as “Nanoweapon” or “DLC”. These coatings are just as smooth if not better than a lot of Nickel Boron coatings. The Nickel Boron coating is still a great coating, but it is not the only great coating on the market.

What is the best bolt carrier group?

When building an AR-15 it is important that you get the best bolt carrier group you can. My go-to has always been Geissele and Bravo Company Manufacturing. If you are budget conscious and still looking to get great BCG, I would highly recommend the BCM BCG, they make one of the best complete uppers on the market.

There are lots of other great BCGs on the market, and I am sure I left some off my list. However, the most important thing when choosing a BCG is a reliability, so make sure you are buying from a reputable manufacturer.