Bolt carrier group (auto version) for your AR15, M16, or M4. Parkerized exterior and chrome lined inside carrier. Machined to USGI specifications.

BCM® (MPI) Complete Bolt Carrier Groups

The BCM® complete bolt carrier group (BCG) is fully assembled and designed for your AR15, M16, or M4. It features a parkerized exterior and a chrome-lined interior. This BCG is machined to USGI specifications and includes the proper Mil-Spec gas key. The gas key is also chrome-lined and heat-treated according to GI specifications. It is secured to the carrier using USGI domestic Grade 8 fasteners and is properly staked to ensure a strong connection and effective gas system function.

The bolt assembly is made from the correct Mil-Spec Carpenter No. 158® steel, shot-peened for added strength, and includes a tool steel extractor and ejector. It also comes with a BCM Extractor Spring and has been HPT (High Pressure Tested) and MPI (Magnetic Particle Inspected).

Before shipping, all BCM Bolt Carrier Groups are test-fired to ensure functionality. As a result, the BCG may show handling marks consistent with our quality control procedures.

Watch the video below to learn more about our quality control for Bolt Carrier Groups:

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Important Note:
According to the Bureau of Alcohol, Tobacco, Firearms and Explosives (BATFE), M16 bolt carriers are not intended solely for converting a weapon into a machine gun and do not form a combination of parts that can assemble a machine gun. An M16 bolt carrier is not classified as a firearm under the GCA or a machine gun under the NFA. It is simply a machine gun part, and its domestic sale and possession are unregulated by federal firearms laws. It is legal to use an M16 machine gun bolt carrier in a semiautomatic AR15-type rifle. Visit our shop page to view more of our catalog here. Learn how to set-up here.