Hello.
Are all AR15 bolt carriers the same and not caliber specific?
A bolt carrier group (BCG) is a collection of parts that work together to cycle a firearm. The three main parts of a BCG are the bolt, the carrier, and the firing pin.
Bolt carrier groups are caliber specific. This means that there is a different BCG for each caliber of firearm. For example, you would use a different BCG for a 5.56mm weapon than you would for a 7.62mm weapon.
The reason that BCGs are caliber-specific is that the dimensions of the various calibers are different. This means that the components of the BCG must be dimensioned differently to properly function with a particular caliber bullet.
When shopping for a BCG, it is important to make sure that you are getting the correct one for your firearm. Many retailers will sell BCGs that are advertised as “universal” or “multi-caliber.” However, these BCGs are usually not true universal designs. They may work with some calibers, but not others.