AR-15 - BCG Facts & What To Know - CIV Tactical

Published on July 1, 2014
Duration: 20:59

This video provides a detailed breakdown of the AR-15 Bolt Carrier Group (BCG), explaining the function and technical specifications of each component. It covers the differences between full-auto and semi-auto carriers, proper assembly and disassembly procedures, and critical measurements like firing pin protrusion and extractor cam out. The instruction comes from an experienced individual in a shop environment, offering practical advice for maintaining and understanding the BCG.

Quick Summary

The AR-15 Bolt Carrier Group (BCG) consists of the carrier body, gas key, cam pin, and bolt head. Key specifications include gas key torque of 35-40 in-lbs, firing pin protrusion of 0.028-0.036 inches, and gas rings with the knife edge facing rearward. Full-auto carriers have a solid rear tail, while semi-auto carriers are relieved.

Chapters

  1. 00:09Introduction to BCG Technical Specs
  2. 00:20BCG Components Overview
  3. 01:17Disassembling the Bolt Carrier Group
  4. 01:50Full-Auto vs. Semi-Auto Carrier Differences
  5. 03:13Carrier Body Details
  6. 04:00Gas Key Specifications
  7. 05:11Bolt Head Details
  8. 06:08Bolt Head Components
  9. 06:37Stripping the Bolt
  10. 07:22Gas Ring Specifications and Directionality
  11. 08:26Stripped Bolt Features
  12. 08:55Firing Pin Protrusion Measurement
  13. 10:23Extractor Specifications
  14. 11:33Extractor Cam Out Measurement
  15. 13:25Adjusting Extractor Cam Out
  16. 14:04Cam Pin Specifications
  17. 14:56Extractor O-Rings Discussion
  18. 15:31Reassembling the Bolt
  19. 16:36Spring Pin Installation
  20. 17:50Reinstalling Extractor and Gas Rings
  21. 18:46Reassembling BCG into Carrier
  22. 19:50Gas Ring Wear Test
  23. 20:40Conclusion and Summary

Frequently Asked Questions

What are the key differences between a full-auto and semi-auto AR-15 bolt carrier?

The primary difference lies in the rear of the carrier body. A full-auto carrier has a solid, full-length rear tail designed to trip the auto sear for automatic fire. A semi-auto carrier has this rear section relieved or cut away to prevent it from engaging the auto sear, ensuring only semi-automatic function.

What is the correct torque specification for the AR-15 gas key screws?

The gas key screws on an AR-15 bolt carrier group should be torqued to 35 to 40 inch-pounds (in-lbs). After torquing, these screws are typically staked to prevent them from loosening during operation.

What is the proper firing pin protrusion for an AR-15 bolt?

For an AR-15 bolt, proper firing pin protrusion is critical for reliable ignition. The specification ranges from a minimum of 0.028 inches to a maximum of 0.036 inches. This ensures the firing pin strikes the primer with sufficient force.

How can I check if my AR-15 bolt carrier group's gas rings are worn?

You can test gas ring wear by hanging the bolt carrier by the bolt head. If the bolt doesn't drop freely under its own weight, the gas rings are likely still good. Alternatively, with the bolt removed, if the bolt doesn't fall freely when stood on end, the rings are not excessively worn.

Should I lubricate the gas rings on my AR-15 bolt carrier group?

No, lubrication is not recommended on the gas rings or any part of the bolt carrier group rearward of them. This area is a non-friction zone, and dry carbon is generally easier to clean than wet, carbonized lubricant.

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