General Thompson will certainly be remembered for his famous “Tommy Gun” or formally adopted as the M1928 or in its later blow-back only form the M1 Thompson. But what about Thompson’s other designs?
Due to the prohibitive costs of the Thompson M1928 (which was nearly three times the price of the M1919 belt-fed machine gun), the US Military went in search of replacements (which ultimately became the M3 “grease gun”). Knowing the end-of-line was coming Auto Ordnance submitted their new design, named the “T2” to the US Army.
The T2 was a large departure from the base M1928/M1/M1A. Manufactured in both .45 ACP and 9mm, it featured a tube design (for reference, similar to the AR-15). The T2 fed from exisiting Thompson magazines (at least for the .45 ACP) and featured a progressive trigger (for reference, similar to the AUG) that fired semi-auto on a short pull and full-auto on a long pull.
During the testing with the US Army with “several thousand rounds” fired, the trigger housing cracked after 750 rounds which was subsequently blamed for 37 of 60 malfunctions. Ignoring the malfunctions, the weapon performed well in environmental testing (sand and mud) due to the closed system. In fact, it was better in said environmental and additional long-distance (100 yards) testing.
However, the weapon was ultimately not selected for a few reasons, which can be seen in the video below. Its a fascinating story.