AR-15 BCG (Bolts Carrier Group) Guide
Posted by Doug Shoemaker on May 25th 2022
If you are a gun enthusiast, you probably learn as much as you can about your favorite firearms. But how much do you know about the AR-15 BCG (Bolt Carrier Group)?
In this article, we share everything you need to know about them.
What is the BCG?
The bolt carrier group is a crucial part of the gun that is the heart and soul of the AR-15. While some elements of the AR-15 are simply in place for extra comfort, speed, or style, the bolt carrier group is necessary for the gun to function correctly. Without this piece operating as intended, the weapon will not fire and will be largely inoperable.
The AR-15 BCG may also be referred to as the "action." It is in charge of loading, firing, and ejecting rounds from the chamber. It houses the bolt and resets the hammer as it moves within the upper receiver.
Unfortunately, AR-15 BCGs get pretty beat up from heavy use, reducing the reliability of your rifle. In which case, you will end up needing to replace them.
Replacing the BCG
There are two ways to replace your AR-15 BCG. The first is to buy one pre-assembled and drop it into your upper. However, you can also opt to buy the individual components and build one yourself. Neither is necessarily better than the other.
How Does the BCG Work?
As mentioned, the AR-15 BCG is responsible for the firing action of the rifle. However, it's a little more complex than that.
When you pull the trigger, the hammer strikes the firing pin and causes the bullet to fire. As the bullet travels down the barrel, the building gas pressure behind the bullet enters the gas block.
The pressure enters the gas key as this gas circles back around the gas tube. This unlocks the bolt and pushes the bolt carrier back. The extractor pulls the spent shell out of the chamber as this happens.
The spring-loaded ejector kicks this cartridge out through the ejection port. Then, the next round can slide into place for the process to begin again.
Different Types of AR-15 BCGs
The next logical question is, "are all BCGs the same?"
The short answer is "no" — there are many variations among types of bolt carrier groups. In addition, there are slightly different configurations that offer various advantages and disadvantages.
One of the significant ways bolt carrier groups differ is their weight and material composition.
Two Main Configurations
There are two standard bolt carrier configurations: an AR-15 style (Semi-Auto) and an M16 style (Full-Auto). The M16 style has a full mass at its tail, while the AR-15 style's bottom is cut out. Keep in mind that although the M16 bolt carrier has been referred to as "Full Auto," it doesn't make your AR fully automatic.
M16 Style
The M16 style action is slightly heavier than the AR-15 style. The M16 style bolt carrier is heavier. As a result, it has a slower cycling rate, which helps your rifle function more reliably and reduces felt recoil.
AR-15 Style
The AR-15 style action is lighter, which increases the cycling rate. This lighter bolt carrier will benefit someone who wants to have a "race gun." A "race gun" is usually modified for speed in competition, but it might require some gas tuning to function reliably.
Besides the two basic bolt carrier group profiles, there are a couple of other features that you can look into when choosing your BCG.
Advanced Coating on AR15 BCG
New generation bolt carrier groups are often coated with an extra layer of protection, such as Titanium Nitride and Black Nitride. These coatings help the BCG withstand corrosion, dirt, and general wear and tear better.
Because this is a rifle component that frequently undergoes quite a bit of battering, the coating can be the difference that helps your action enjoy a longer life.
In addition, some advanced coating like the nickel boron requires less lubricant. As a result, the parts slide together smoothly and decrease the risk of jamming or other malfunctions. Therefore, opting for the nickel boron coating increases both the overall reliability and the general durability of your bolt carrier grip.
Lightweight/Low Mass AR15 BCG
The lightweight profile option is slightly different from the AR-15 and M16 profiles. As a result, it does not benefit from the extra weight that the standard M16 profile bolt carrier group does.
However, its highly lightweight nature makes the rifle faster, smoother, and less felt recoil.
Benefits of Upgrading Your AR-15 BCG
There are countless ways to upgrade, improve, and make your gun more personalized. Every modification and upgrade will bring distinct advantages and disadvantages. Consider where your rifle lacks and where you'd like to see specific improvement.
Here are a few of the benefits you might experience when you decide to upgrade your AR-15 BCG.
Increased Reliability
There's nothing more frustrating than a firearm that fails when you're counting on it. While there are numerous reasons a gun might jam or fail at the last minute, a quality BCG will decrease the odds of it happening.
Increased Durability
The more you use your weapon, the more wear it will take and the faster it will break down. Your BCG, in particular, is especially susceptible to wear and damage. It will degrade before too long no matter how careful and responsible you are simply because of what it does.
No action will last forever, but it's possible to extend your BCG's lifespan by purchasing and installing quality parts.
Increased Speed
Different upgrade options increase the speed at which your bolt carrier group releases rounds. A BCG built for faster cycling can result in this particular benefit to your rifle.
Increased Ease and Smoothness
By upgrading to higher-quality parts, you can improve the performance of your AR-15s BCG.
Our AR-15 BCG Recommendations
While many companies are out there, a few manufacturers offer the best and most reliable parts. If you're in the market for an AR-15 BCG, we would recommend:
All of the companies listed here are known for crafting solid and reliable parts. No matter what specific type of bolt carrier group you're looking for, you'll find something reliable from one of these companies.
Shop AR-15 Bolt Carrier Groups
With a basic understanding of AR-15 BCGs, the next step is to start shopping! See our inventory here.
Don't forget to subscribe to our email below to see new arrivals to the store, deals, and news in the firearms industry.