Ask Ian: Why Didn't The M3 Grease Gun use Thompson Mags?

Published on July 28, 2022
Duration: 7:55

This guide explains why the M3 Grease Gun did not use Thompson submachine gun magazines, despite potential logistical benefits. Expert Ian McCollum details how the M3's design prioritized cheap, rapid mass production using stamped sheet metal and a simple single-feed magazine, contrasting with the Thompson's complex T-shaped lug requiring a milled receiver. This fundamental difference in manufacturing and retention mechanisms made cross-compatibility impossible.

Quick Summary

The M3 Grease Gun did not use Thompson magazines due to fundamental design differences driven by manufacturing. The M3's stamped construction required a simple single-feed magazine, while the Thompson's complex T-shaped lug necessitated a precisely milled receiver track, making them incompatible.

Chapters

  1. 00:00Introduction: The M3 vs. Thompson Mag Question
  2. 00:33M3 Design Philosophy: Stamped Metal & Sten Influence
  3. 01:34M3 Magazine Lineage: Single-Feed Simplicity
  4. 02:25Modern Retention Systems Explained
  5. 03:13The Thompson Magazine's T-Shaped Lug
  6. 04:58Other Firearms Using Thompson-Style Mags
  7. 06:43Conclusion: Manufacturing Dictates Design

Frequently Asked Questions

Why couldn't the M3 Grease Gun use Thompson submachine gun magazines?

The M3 Grease Gun used a simple, single-feed box magazine designed for its stamped sheet metal construction. In contrast, the Thompson magazine features a complex T-shaped lug that requires a precisely milled receiver track for secure retention, making the two incompatible due to differing manufacturing methods and design priorities.

What was the primary design goal for the M3 Grease Gun's magazine?

The primary design goal for the M3 Grease Gun's magazine was simplicity and cost-effectiveness to facilitate rapid, mass production. It adopted a single-feed box magazine design, influenced by firearms like the British Sten gun, which was easier and cheaper to manufacture than the more complex Thompson magazine.

How does the Thompson magazine's retention system differ from typical stamped firearm magazines?

The Thompson magazine utilizes a robust T-shaped lug on its rear, requiring a corresponding milled groove within the firearm's receiver for secure engagement. This contrasts with most stamped firearms, including the M3 Grease Gun, which employ simpler spring-loaded catches that engage a basic cutout on the magazine body.

More Gunsmithing & DIY Videos You Might Like

More from Forgotten Weapons

View all →