LMT 12” Piston Barrel Revisited | Group Testing and Inspection

Published on December 18, 2025
Duration: 15:14

Preston Moore revisits the LMT 12-inch piston barrel, detailing its specifications and conducting a thorough physical and borescope inspection. The review highlights updated features but also reveals significant chrome flaking issues. Performance testing with various ammunition types provides empirical data on accuracy, with results analyzed using practical metrics.

Quick Summary

The LMT 12" piston barrel, reviewed by Preston Moore, features a 5.56 NATO chamber, 1:7 twist, and 4150 CMV chrome-lined construction. While updated features were noted, borescope inspection revealed significant chrome flaking in the rifling, a recurring quality concern impacting durability and accuracy.

Chapters

  1. 00:00Introduction and Specifications
  2. 01:24Physical Inspection and Gauging
  3. 02:33Borescope Inspection
  4. 04:54Shooting Setup and Methodology
  5. 06:19Group Testing and Analysis

Frequently Asked Questions

What are the key specifications of the LMT 12" Piston Barrel?

The LMT 12" piston barrel is chambered in 5.56 NATO, features a 1:7 twist rate, is constructed from 4150 CMV, and is chrome-lined and cryogenically treated. It weighs approximately 2.16 pounds.

What quality control issues were found with the LMT 12" Piston Barrel?

A significant issue identified via borescope was chrome flaking within the rifling. Additionally, headspace testing indicated it passed minimum and field gauges but failed a specific NOGO gauge.

How did the LMT 12" Piston Barrel perform in group testing?

Testing with Federal 77gr SMK yielded a 1.642 MOA 30-shot group. Winchester M193 55gr produced a 4.467 MOA group. Performance with IMI Razor Core 77gr was poorer at 3.904 MOA.

What is the significance of chrome flaking in a firearm barrel?

Chrome flaking is a manufacturing defect where the chrome lining peels away. This can negatively impact accuracy, reduce corrosion resistance, and potentially lead to premature wear and failure of the barrel.

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