WHAT IS A BOLT CARRIER GROUP?

The Bolt Carrier Group (BCG) is a critical component of the AR-15. The BCG is the “action” of the rifle. It loads a new round into the chamber, fires that round, extracts and ejects the spent casing, cocks the hammer and repeats the process.

The BCG is subject to extreme pressures and temperatures as it harnesses the gas from the Direct Impingement (DI) gas system to cycle the rifle. With each shot the BCG violently travels to the rear of the rifle into the buffer tube where it is stopped and returned by the buffer and buffer spring.

Even in a semi-automatic firearm, this process can happen multiple times per second depending on the skill of the shooter.

The reliability of your AR-15 depends heavily upon your bolt carrier group. Choosing a BCG can be overwhelming given the multitude of choices on the market. At Primary Arms, we carry more than 100 different BCGs. Understanding which BCG is right for you will involve an examination of your intended use, performance requirements, budget and desired aesthetics.

Is your rifle a budget build? Defensive carbine? Hunting rifle? Work horse utility rifle? Lightweight race gun? Competition shooter? This buyer’s guide will explain the various types of bolt carrier groups, coatings and what differentiates one from another.

An AR-15 bolt carrier group consists of the following components as identified in the photo below; the carrier, bolt assembly which includes the extractor, gas key, cam pin, firing pin retainer pin, firing pin.