Grease Gun: Examining the M3/M3A1 Submachine Gun

Compared to most U.S. infantry weapons of World War II, the M3 submachine gun is not especially well known. This is even more remarkable given that it is the longest-serving SMG in U.S. military history, having been used from 1942 to 1992.

The M3’s resemblance to the tool used to lubricate automobiles resulted in its nickname, the “Grease Gun.” Many of those who do recognize the M3 may know it more by that title than its official designation. The M3 has been portrayed onscreen a few times, including the film “The Dirty Dozen” and in HBO’s “Band of Brothers.”

A New Direction

Development of the M3 began in 1941 when the U.S. Army Ordnance Board became interested in an inexpensive, mass-produced submachine gun akin to the British Sten Gun. This in itself was quite a turnaround as, unlike many European armies, the U.S. Army had never really been especially enamored with SMGs. At the time, the U.S. submachine gun was the Thompson, which had been adopted to a large extent because it was available and already in production at the start of the war.

The Thompson was effective but heavy and expensive. Based on a list of requirements submitted by the Army, specs were developed for an all-metal weapon, chambered for the .45 ACP cartridge, capable of either semi- or full-auto fire, having a low cyclic rate and capable of being inexpensively mass produced. The original specifications had offered .30 Carbine as an alternative to .45 ACP, but the pistol caliber was chosen. To save costs, the capability of firing on semi-auto was eliminated, so the M3 could only be fired on full-auto.