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











