Understanding the AR-15 Bolt Carrier Group: A Comprehensive Guide
The AR-15 bolt carrier group (BCG) is a critical component of the AR-15 rifle, responsible for the ejection of spent casings and the feeding of new rounds into the chamber. In this detailed guide, we will explore the various parts that make up the AR-15 BCG and their functions.
What is a Bolt Carrier Group?
The bolt carrier group is a collection of parts that work together to cycle the action of the firearm. It includes the bolt, carrier, gas key, and various other components. The BCG is the heart of the rifle’s action, and understanding its parts is essential for anyone looking to maintain or modify their AR-15.
Parts of the AR-15 Bolt Carrier Group
| Part | Description |
|---|---|
| Bolt | The bolt is the main moving part of the BCG. It locks into the receiver and moves back and forth to cycle the action. |
| Carrier | The carrier is a tube that holds the bolt and other components. It is responsible for guiding the bolt’s movement and housing the gas key. |
| Gas Key | The gas key is a flat piece of metal that secures the carrier to the bolt. It also allows gas to pass from the barrel to the carrier, driving the bolt back and forth. |
| Extractor | The extractor is a spring-loaded piece that grabs the rim of the spent casing and pulls it out of the chamber. |
| Ejector | The ejector is a spring-loaded piece that pushes the spent casing out of the rifle. |
| Chamber Locking Lug | The chamber locking lug is a part of the bolt that locks into the receiver, securing the round in the chamber. |
| Bolt Face | The bolt face is the part of the bolt that contacts the primer of the round, igniting it. |
Function of the Bolt Carrier Group
The BCG operates through a series of steps:
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When the trigger is pulled, the hammer strikes the firing pin, which ignites the primer of the round.
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The expanding gases from the primer push the bolt back, cycling the action.
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The extractor grabs the spent casing and pulls it out of the chamber.
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The ejector pushes the spent casing out of the rifle.
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The carrier continues to move back, feeding a new round into the chamber.
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The bolt moves forward, locking into the receiver and preparing for the next shot.
Types of Bolt Carrier Groups
There are several types of BCGs available for the AR-15, each with its own advantages and disadvantages:
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Full-Auto BCG: Designed for full-auto fire, these BCGs are heavier and more durable than semi-auto BCGs.
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Semi-Auto BCG: The most common type of BCG, these are designed for semi-auto fire and are lighter than full-auto BCGs.
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Enhanced BCG: These BCGs are designed for improved performance and durability, often featuring features like heat treatment and increased strength.
Upgrading Your Bolt Carrier Group
Upgrading your BCG can improve the performance and reliability of your AR-15. Some popular upgrades include:
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Heavy Duty BCG: These BCGs are designed for heavy use and can handle more rounds per minute.
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Chrome Bolt: A chrome bolt can reduce wear and improve the longevity of your BCG.
