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Bolt Carrier Group Parts Diagram: Exploring The Heart Of Your Firearm

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When it comes to understanding the inner workings of your firearm, the bolt carrier group (BCG) is a crucial component that deserves your attention. This intricate assembly plays a vital role in the proper functioning of your firearm, and having a clear understanding of its parts diagram can help you maintain and optimize its performance. In this article, we will take a closer look at the various components that make up a bolt carrier group.

The Bolt

At the heart of the BCG is the bolt itself. This robust and durable component is responsible for chambering the rounds, extracting spent casings, and ejecting them from the firearm. It contains several essential parts, including the bolt head, bolt body, extractor, extractor spring, and ejector.

The Carrier

The carrier is the part that houses the bolt and provides the necessary support for its movement. It connects the bolt to the gas key, allowing the transfer of gas pressure from the gas tube to the bolt assembly. The carrier also includes the firing pin retaining pin, cam pin, and firing pin.

The Gas Key

Located on top of the carrier, the gas key is a critical component that connects the gas tube to the BCG. It receives the high-pressure gas from the gas tube and directs it into the carrier, facilitating the cycling of the bolt. The gas key is secured to the carrier with two screws and must be properly tightened to prevent gas leaks.

The Gas Rings

The gas rings, typically three in number, are positioned around the bolt body. These rings provide a seal between the bolt and the inside of the carrier, ensuring that the gas pressure is directed in the right direction to cycle the firearm reliably. Over time, these rings may wear out and need replacement to maintain optimal performance.

The Cam Pin

The cam pin is responsible for controlling the rotation of the bolt inside the carrier. It features a cam-shaped head that interacts with the corresponding cam path in the upper receiver, allowing the bolt to lock and unlock during the firing cycle. Proper lubrication of the cam pin is essential to ensure smooth operation.

The Firing Pin

The firing pin is a slender rod-like component that sits within the bolt and strikes the primer of the cartridge to initiate ignition. It is essential for the firing pin to move freely and strike with sufficient force to reliably ignite the primer. Regular cleaning and inspection of the firing pin are necessary to prevent malfunctions.


Understanding the bolt carrier group parts diagram is crucial for firearm enthusiasts and owners who want to maintain and optimize the performance of their firearms. By familiarizing yourself with the various components, such as the bolt, carrier, gas key, gas rings, cam pin, and firing pin, you can ensure proper functioning and reliability. Regular maintenance, inspection, and replacement of worn-out parts will help extend the lifespan of your bolt carrier group and enhance your shooting experience. Stay safe and happy shooting!