Heavier is Better || Short 308 (Part 2)

Published on November 8, 2020
Duration: 5:36

This video details the installation of a CMMG bolt tuning kit on a short-barreled .308 rifle (CMMG Mk3) to address over-gassing and ammunition selectivity issues. The kit increases the reciprocating mass of the bolt carrier, significantly reducing felt recoil when firing unsuppressed with lighter ammunition. While effective for unsuppressed use, an adjustable gas block is still recommended for reliable suppressed operation.

Quick Summary

A CMMG bolt tuning kit increases the reciprocating mass of a short-barreled .308 rifle's bolt carrier, significantly reducing felt recoil and improving function with lighter ammunition. While effective unsuppressed, an adjustable gas block is still recommended for reliable suppressed shooting on these platforms.

Chapters

  1. 00:00Intro: Short .308 Battle Rifle Project
  2. 00:14Initial Ammunition Selectivity Issues
  3. 00:32Exploring Recoil Solutions
  4. 00:44Introducing the Bolt Tuning Kit
  5. 01:09Testing Bolt Tuning Kit Performance
  6. 01:20Unsuppressed Firing (No Kit)
  7. 01:40Unsuppressed Firing (With Kit)
  8. 01:57Suppressed Firing (With Kit)
  9. 02:23Unsuppressed Kit Performance Summary
  10. 02:44Visual Recoil Comparison
  11. 03:33Suppressed Performance Limitations
  12. 04:04Future Plans & Fireballs
  13. 04:21Final Fireball Demonstration

Frequently Asked Questions

What is a bolt tuning kit and how does it improve a short-barreled .308 rifle's performance?

A bolt tuning kit, like the one from CMMG, adds weight to the rear of the bolt carrier. This increases the reciprocating mass, slowing down the bolt's cycle. For short-barreled .308 rifles prone to over-gassing, this helps mitigate issues with lighter ammunition and significantly reduces felt recoil when unsuppressed.

Can a bolt tuning kit make a short-barreled .308 rifle run reliably when suppressed?

While a bolt tuning kit can improve unsuppressed function and reduce recoil, it is often not sufficient on its own for reliable suppressed operation in extremely short-barreled rifles. These platforms may still require an adjustable gas block to fine-tune gas pressure and ensure proper cycling with a suppressor attached.

What are the signs that a short-barreled .308 rifle might need a bolt tuning kit?

Signs include ammunition selectivity issues, where the rifle struggles to cycle lighter loads, and excessive felt recoil. If the rifle is significantly over-gassed, especially with certain ammunition types, a bolt tuning kit can be a valuable modification to improve its functionality and shootability.

What is the weight difference with a CMMG bolt tuning kit installed?

The CMMG bolt tuning kit adds substantial weight to the bolt carrier. In the video, the modified bolt carrier with the kit weighed 1.26 lbs, compared to the original bolt carrier's implied lighter weight. This increased mass is key to its recoil-reducing and cycling-smoothing effects.

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