A full-auto bolt carrier group is a rifle component that enables a firearm to fire in fully automatic mode. It replaces the standard bolt carrier group in an AR-15 rifle and converts it into a machine gun. Full auto bolt carrier groups are illegal to possess in most states without the proper license, and they are subject to strict regulations and controls under federal law.
A full-auto bolt carrier group (BCG) is a component of an AR-15 rifle that allows the weapon to fire in fully automatic mode. The BCG contains a metal piece called the “carrier” that slides back and forth inside the receiver, and a metal piece called the “bolt” that moves forward and backward inside the carrier. When the trigger is pulled, it causes the bolt to move forward, stripping a round from the magazine and chambering it. When the round is fired, the gas pressure created by the explosion pushes on the piston head, which in turn pushes on the carrier, causing it to move rearward. This movement extracts the spent casing from the chamber and ejects it from the weapon. As soon as the carrier reaches the rear of its travel, a spring inside the receiver pushes it back forward, chambering another round from the magazine. This process continues as long as the trigger is held down and there are rounds in the magazine.
Bolt carrier groups come in two different varieties: full-auto and semi-auto. The main difference between the two is the shape of the carrier. The carrier on a full auto BCG has a larger “shelf” on the underside, which extends further back than the shelf on a semi-auto BCG. This shelf engages with the sear, which is what holds the Bolt Carrier Group in the rear position when you release the trigger. Without this engagement, the Bolt Carrier Group would move forward and chamber another round as soon as the previous round was fired, resulting in a fully automatic weapon. The other difference is that full auto BCGs typically have a heavier carrier, which helps to dampen the recoil of the weapon.
A full-auto bolt carrier group is a complete assembly that includes the bolt carrier, firing pin, retaining pin, and cam pin. It allows a rifle to fire automatically. A semi-auto bolt carrier group is similar but does not have the necessary components to fire automatically. It is only capable of semi-automatic firing.
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.
Check this video:
A full-auto bolt carrier group (BCG) is a component of an automatic firearm that performs the key task of chambering a round and firing it. It is typically composed of three parts: the bolt, the bolt carrier, and the firing pin.
The bolt is a cylindrical component that is inserted into the gun’s barrel. It houses the cartridge and has locking lugs on its front that lock into corresponding recesses in the barrel extension to form a tight seal. The bolt carrier sits on top of the bolt and contains recoil springs and guide rods that help propel it rearward upon firing. The firing pin is a slender rod located at the rear of the BCG that projects through a small hole in the Bolt Carrier and strikes the primer of the chambered cartridge to set off the round.
1 – (above) – Full Auto Capable TR-BCA
2 – (below) – Semi Auto TR-BCA-SEMI