Few weapons are more closely associated with World War II than the M3 Submachine Gun – also known as the "Grease Gun" for its distinctive shape. The Grease Gun actually saw service for decades after the war, becoming the standard-issue weapon for crews manning the M-48 through M-60 battle tanks. It was the longest-serving SMG, from 1942 to 1992.
Its World War II use of the .45 round, already in use by the Thompson submachine gun and the M1911 pistol, made it a weapon that could be easily adapted for more situations and more troops. Sadly, it was also the weapon's ultimate undoing.
A U.S. soldier from the Army's 3rd Infantry Division fires an M3 submachine gun during a training exercise.
By many accounts, the M3 was still in use by the 1990s. Unlike many of its contemporary weapons, the Grease Gun did not have adjustable sights and was mainly intended for tank crews to use in close quarters so they could get back in the tank and continue firing the big gun. The stopping power of a spray of .45-caliber rounds will go a long way toward making that possible.
Its main competitor was the Thompson submachine gun, but the Thompson had problems of its own. It was heavy and expensive to build. The U.S. wanted a more lightweight model for tankers and paratroopers, but didn't want to spend all the money per item. The M3 was the answer, despite a few shortcomings.
A U.S. troop in Vietnam carrying the M3 SMG.
The short barrel, while making it possible for crews to carry around the cramped quarters of a tank, also added to its inaccuracy. The real trouble comes after a tanker has to expend all of his pre-loaded magazines. The M3 submachine gun has a magazine that appears to be longer than its barrel. A large magazine is a great thing for a fully-automatic weapon like the Grease Gun, but as anyone who's sprayed an automatic before knows, the bullets run out really fast.
Tankers were issued four magazine for the tank's two grease guns. Once they were out, the magazines would have to be reloaded. Now imagine trying to fully reload an M3 submachine gun magazine, especially when it's almost full.
The M3 cost around .00 to produce in 1942, equal to about 0.00 today.
Eventually, the M3 was phased out by more efficient weapons for anyone who might need a personal weapon on the battlefield as the .45 round gave way to the 5.56 and 9mm standards.
After the 1991 Gulf War, the M3 began to disappear from the U.S. Military altogether after some 50 years in service.