Components of the Bolt Carrier Group: Buying and Beyond

One of the most important things to remember about the AR 15, especially when thinking about function, is that the initial design was meant for military use. Sure, many owners today use the AR for hunting, home defense, and range time, but when the AR 15 was initially created, it was meant to fit a specific set of needs requested by the U.S. military. Those requests, as you may imagine, shaped a lot of the form and function of the AR 15/M16. One of the most effective and important features is how the AR 15 fires and reloads, which is powered by the bolt carrier group. If you’re new to the AR 15 world and looking to learn more about the way this firearm functions, here’s what you need to know about the bolt carrier group and how it can affect firing the AR 15.


AR 15 – Form and Function

When the AR 15 was being designed, one of the primary features that the U.S. military required was the ability to fire a lightweight, high-velocity round with better accuracy. The idea was to allow service men to carry more ammunition, but potentially need to use less of it. Sounds like the magical ideal, right? Well, the goal of lighter rounds and better accuracy was all well and good, except a smaller caliber high-velocity round wouldn’t do a lot of good if the soldier had to stop and reload in between each shot. So, when ArmaLite submitted their designs for the AR 15, one of the other key features for their firearm design was the semi-automatic design. Not only did the AR 15 offer a lighter firearm than the military’s previous firearms, it was made to fire, expel the spent cartridge, and load a new round without any manual assistance. The way it manages this is through the movement of the bolt carrier group and the direct gas impingement system.


What the Bolt Carrier Group Does

If those sound like foreign terms, don’t worry. It’s actually much more simple than it sounds. The basic way it works is this: the AR 15 uses compressed gas to move the bolt carrier group, and the way all the parts connect mean the gas is used to not only fire the round, but to also help it eject the spent cartridge and load the next round without any extra steps from the user. In the AR 15, the direct impingement system uses the gas from firing to move the bolt carrier group. As the bullet continues down the barrel, the gas pressure behind it will go up into the gas tube, pushing the bolt carrier group back. As the gas from firing comes back, all that built up pressure hits the firing pin, pushing bolt and bolt carrier back. When it does this, the spring-loaded function at the head of the bolt forces the spent cartridge out through the ejection port and allows the next round to slide up into the chamber. A weighted spring pushes the bolt carrier group forward again, locking into place securely against the chambered round. The old round is kicked out and the new round is ready to go pretty much instantly.

Smooth Action

The bolt carrier group is what makes the difference between a quick and smooth firing and reloading process and a glitchy one. The key components of the bolt carrier group starts with the carrier, which serves as the external housing for the bolt and has the gas key attached to it. This is important to clean and check regularly because if the screws attaching the gas key come loose, the bolt carrier group will stop working smoothly. The bolt itself is the component that helps guide the next round into the chamber and, once it has been fired, ejects that spent cartridge. The charging handle attaches to the bolt carrier group and can help cycle through the action without firing, in order to ensure a round is chambered and locked into place correctly. While it isn’t likely to have much, if any, effect on accuracy while firing, the bolt carrier group works with the direct impingement system and can affect the recoil pulses and the smoothness of the action.


When it comes to firing your AR 15, you want a bolt carrier group that will hold up to the repeated use without jamming or coming loose—and this is where custom AR parts from a specialized manufacturer can make all the difference. Shop Bootleg, Inc. today to experience the difference in our custom bolt carrier group options!

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