The Bolt Carrier Group (BCG) is often referred to as the “heart” of the AR-15 rifle, and it plays a central role in the firearm’s functioning. Comprising several critical components, the BCG is responsible for chambering, firing, extracting, and ejecting rounds. Here’s an overview of the essential parts within the AR15 Parts:
1. Bolt: The bolt is a key component of the BCG and plays a crucial role in the firing sequence. When the trigger is pulled, the bolt is driven forward, chambering a round and locking into the barrel’s extension. The bolt contains the firing pin and extractor claw, which are vital for ignition and extraction.
2. Carrier: The carrier is the component that houses the bolt and moves back and forth within the upper receiver when the rifle is fired. It directs the energy from the expanding gas into the bolt to cycle the action.
3. Firing Pin: The firing pin is a small, cylindrical pin within the bolt. When struck by the hammer, it strikes the primer of the chambered round, initiating the firing sequence.
4. Cam Pin: The cam pin is a small, cylindrical pin that secures the bolt and allows it to rotate as it moves forward and backward. This rotation is necessary for proper locking and unlocking of the bolt.
5. Gas Rings: The gas rings are small rings that create a gas seal between the bolt and the inside of the carrier. This seal ensures that gas pressure is directed correctly to cycle the action. Typically, three gas rings are used in the BCG.
6. Extractor and Extractor Spring: The extractor claw grabs the rim of the spent cartridge case and extracts it from the chamber during the cycling process. The extractor spring provides tension to the extractor claw, ensuring reliable extraction.
7. Ejector and Ejector Spring: The ejector is a small, spring-loaded pin within the BCG that forcefully ejects the spent cartridge case from the ejection port. The ejector spring provides tension to the ejector.
8. Bolt Carrier Key: The bolt carrier key is a small, rectangular piece that is staked onto the top of the carrier. It provides a gas path for the expanding gas to enter the BCG, pushing it backward to cycle the action.
9. Firing Pin Retaining Pin: The firing pin retaining pin holds the firing pin in place within the bolt.
10. Gas Key Screws: These screws secure the gas key to the bolt carrier key. They are crucial for maintaining a proper gas seal and preventing gas leaks.
11. Gas Key: The gas key is a rectangular piece that interfaces with the gas tube. It directs gas into the carrier to cycle the action. The gas key is staked to the carrier to prevent it from loosening.
The BCG is subject to significant stress and heat during firing, making it critical to choose high-quality components for reliability and durability. Many manufacturers offer different finishes and coatings for BCG parts, such as chrome, nickel boron, and nitride, which can enhance corrosion resistance and ease of cleaning. Regular cleaning and maintenance of the BCG are essential to ensure proper functioning and extend the life of your AR-15.