CMMG MK3 Short Barrel 308 AR 10 Pistol

Published on October 4, 2020
Duration: 17:38

This video reviews the CMMG Mk3 Short Barrel 308 AR-10 pistol, highlighting its capabilities and limitations. The presenter discusses the concept of a short-barreled .308, its potential for barrier penetration, and the specific features of the CMMG Mk3. Testing reveals unexpected ammunition preferences, with heavier bullets stabilizing better than lighter ones. The video also addresses reliability issues related to the mid-length gas system and over-gassing with certain ammunition types, suggesting the need for an adjustable gas block for optimal performance, especially when suppressed.

Quick Summary

The CMMG Mk3 Short Barrel 308 pistol features a 12.5-inch barrel and a mid-length gas system. Testing revealed it stabilizes heavier bullets (175-180 grain) better than lighter ones (150 grain). Over-gassing was observed with lighter loads, leading to reliability issues. An adjustable gas block is recommended for optimal performance and suppression.

Chapters

  1. 00:01Introduction
  2. 00:20Concept of Short Barrel 308
  3. 01:31CMMG Mk3 Overview
  4. 02:44Banshee 200 Series Mk3 Details
  5. 03:13Barrel Specifications
  6. 03:37M-LOK Handguard
  7. 03:50Sling Plate and Brace
  8. 04:54Why a Short Barrel 308?
  9. 05:34Velocity Testing
  10. 05:48Accuracy Testing
  11. 06:25Fiocchi 150 Grain Test
  12. 06:46175 Grain Test
  13. 06:58Sierra Match King 180 Grain Test
  14. 07:13Accuracy Results Analysis
  15. 09:37Gas System Recap
  16. 10:01Ammunition Selectivity Issues
  17. 11:00Over-Gassing Evidence
  18. 13:06Malfunction Demonstration
  19. 14:16Identified Problem
  20. 15:04Future Plans
  21. 15:11Adjustable Gas Block Need
  22. 16:31Project Iterations
  23. 16:50Outro

Frequently Asked Questions

What are the key specifications of the CMMG Mk3 Short Barrel 308 pistol?

The CMMG Mk3 features a 12.5-inch, 1:10 twist, medium taper 4140 barrel threaded at 5/8x24. It has a mid-length gas system, an M-LOK handguard, and a single-stage mil-spec style trigger breaking under seven pounds. The pistol weighs around 7 pounds unloaded and has an overall length of 30 inches.

Does the CMMG Mk3 Short Barrel 308 pistol perform better with heavier or lighter .308 ammunition?

Testing indicated that the CMMG Mk3 performed better with heavier bullets, specifically 175 and 180 grain loads, which stabilized more effectively. Lighter 150 grain loads showed signs of poor stabilization, resulting in torn paper and less consistent bullet holes.

What reliability issues were observed with the CMMG Mk3 Short Barrel 308 pistol?

The firearm exhibited signs of over-gassing, particularly with 150 grain .308 Winchester ammunition. This resulted in flattened brass and malfunctions where casings were smashed against the deflector, indicating the carrier speed was too fast for the gas system's configuration.

What modifications are recommended for the CMMG Mk3 Short Barrel 308 pistol?

Due to its ammunition selectivity and potential over-gassing, installing an adjustable gas block is highly recommended. This modification will allow for better tuning of the gas system, improving reliability with a wider range of ammunition and especially for suppressed shooting.

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