SOTAR Secret Shopper - Ruger AR556 - Part 3.8/4 - Fitting Buffer Tube/Receiver Extension

Published on February 21, 2025
Duration: 3:56

This video details a gunsmithing fix for Ruger AR-556 rifles experiencing bolt carrier key clearance issues. The instructor demonstrates how to modify the receiver extension (buffer tube) by filing a notch and smoothing the face to allow the buffer retainer to function correctly while gaining an extra rotation. This modification increases the critical gap between the bolt carrier key and the lower receiver, preventing potential damage.

Quick Summary

This AR-15 gunsmithing guide details how to modify the receiver extension (buffer tube) to fix bolt carrier key strike issues. By filing a notch and smoothing the face of the tube, you can ensure the buffer retainer functions correctly and gain an extra rotation, increasing the critical clearance between the carrier key and lower receiver.

Chapters

  1. 00:00Introduction & Series Update
  2. 00:23The Carrier Key Strike Problem
  3. 00:36Understanding the Clearance Issue
  4. 01:04Potential Fixes: Quarter & Buffer Tube Swap
  5. 01:40The Gunsmith Fix: Modifying Receiver Extension
  6. 01:53Buffer Retainer Interference
  7. 02:17Grinding vs. Notching the Buffer Tube
  8. 02:43Filing the Notch and Face
  9. 03:10Fitting and Checking Clearance
  10. 03:36Result: Increased Gap & Buffer Retainer Function
  11. 03:46Conclusion

Frequently Asked Questions

What is the primary issue addressed in this AR-15 modification video?

The video addresses the problem of the bolt carrier key striking the lower receiver on AR-15 style firearms, specifically noted in Ruger AR-556 models. This issue can be exacerbated by suppressors or hot ammunition.

How can one check for bolt carrier key clearance issues on an AR-15?

A simple method to check for adequate clearance is to use two US quarters stacked together as a gauge. This simulates the space between the bolt carrier key and the lower receiver when the buffer and spring are collapsed.

What is the recommended gunsmithing fix for AR-15 carrier key strike problems?

The recommended fix involves modifying the receiver extension (buffer tube) by filing a notch in its lower portion to accommodate the buffer retainer and smoothing its face. This allows for an extra rotation of the tube, increasing clearance.

Why is it important for the buffer retainer to function correctly when modifying the receiver extension?

The buffer retainer must pop up into its designated spot to hold the buffer in place when the upper receiver is removed. If the receiver extension protrudes too far or isn't properly modified, it can prevent the upper receiver from closing.

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