A bolt carrier group, or BCG, is a crucial component of an AR-15 rifle. It is responsible for housing the bolt and carrier assembly, which are the parts of the rifle that cycle the ammunition. The BCG is what allows your AR-15 to fire automatically. You can also click on this site if you want to purchase the best bolt carrier group for rifles.
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There are two main types of BCGs on the market: complete units and stripped units. Complete BCGs come with all of the necessary parts assembled, while stripped units do not. Stripped units are less expensive but require more work to assemble.
The most important part of a BCG is the bolt carrier assembly. This is the part that contains the bolt and carrier, which are responsible for chambering and firing rounds. The bolt is made out of heat-treated steel and contains seven locking lugs that ensure a tight seal with the barrel extension. The carrier is made out of machined aluminum and houses the firing pin.
Finally, it is important to ensure that your BCG is compatible with your upper receiver. Most BCGs are designed for use with mil-spec upper receivers, but there are some that are designed for use with non-mil-spec receivers as well. Be sure to check with the manufacturer of your upper receiver before making a purchase.