What is the difference between Full Auto Bolt Carrier Group and standard BCG?
A full-auto bolt carrier group includes the bolt, bolt carrier, and firing pin. It is used in firearms that are capable of fully automatic fire. The bolt is locked into the barrel extension by the rotating cam pin during firing. Upon recoil, the inertia of the bolt carrier forces it to continue rearward, stripping a round from the magazine and chambering it. At the same time, the extractor pulls the spent cartridge case from the chamber and ejects it from the firearm. The compressed gas then enters through a port drilled into the barrel extension and pushes on the piston head which actives the hammer. The hammer strikes the firing pin, igniting the primer and firing the cartridge. The Bolt Carrier Group is what makes a rifle an automatic weapon.
A semi-auto bolt carrier group includes all of the same parts as a full auto BCG, except the auto sear. The auto sear is what activates the full auto function of the BCG. Without the sear, the BCG will only fire one round per trigger pull.
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