Reproduction GX-607 and XM-177 Moderators: Do They Work?

Published on February 6, 2026
Duration: 12:46

This video provides an expert-level examination of reproduction XM-177 and GX-607 moderators by Liemohn Manufacturing. Ian McCollum details their historical purpose in Vietnam for reducing the excessive noise of short carbines, presents live-fire sound test data from 1968, and discusses the internal design and durability. The legal implications, including the 1975 ATF ruling classifying them as suppressors, are thoroughly covered, along with current pricing and NFA requirements.

Quick Summary

Liemohn Mfg offers functional reproduction XM-177 and GX-607 moderators. Historical 1968 tests showed these devices reduced sound from ~161.7 dB to 159-160 dB. Their robust internal design withstands full-auto fire. Due to an ATF ruling classifying them as suppressors, NFA tax stamps are required for ownership.

Chapters

  1. 00:00Introduction to XM-177 Clones
  2. 00:54Liemohn Mfg Reproductions
  3. 01:10Historical Context & Purpose
  4. 03:26Live Fire Sound Testing
  5. 04:281968 Technical Test Data
  6. 05:18Internal Design & Durability
  7. 08:32Legal Status & ATF Ruling
  8. 11:05Pricing & Market Availability

Frequently Asked Questions

Did Colt's XM-177 moderators actually reduce sound?

Yes, historical 1968 test data shows that Colt's moderators on XM-177 carbines reduced sound levels from approximately 161.7 dB for a standard rifle to 159-160 dB for the moderated carbine.

Why were XM-177 moderators recalled from commercial sales?

The ATF ruled in 1975 that these devices legally qualified as suppressors because they reduced sound. This classification led Colt to cease commercial sales and recall the devices.

What is the purpose of the internal design of these moderators?

The moderators feature small expansion chambers and thick walls. This robust design allows them to withstand extreme stress, such as full-auto 'burn-down' tests involving firing many rounds in rapid succession.

Are Liemohn Mfg reproduction moderators legal to own?

Yes, Liemohn Mfg offers functional reproduction moderators. However, due to the ATF's classification of these devices as suppressors, ownership requires compliance with NFA regulations, including a tax stamp.

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