The M3 submachine gun was adopted into service by the US Army in December of 1942.  This .45cal submachine gun had a 30-round magazine and was considered superior to the its counterpart, the Thompson submachine gun. The M3 was not only cheaper to produce than the Thompson, it was also lighter and more accurate.  This submachine gun design was called the ‘Grease Gun’ or ‘the Greaser’ as it resembled the grease tool used by mechanics.


Step back in time as you step into the Firearms and Ordnance Gallery at the Armed Forces History Museum.  Here, reality awakens within, as you marvel at the weapons and experience a sense of their power.  A US M3 Submachine gun is a part of this extensive collection of authentic weapons from around the world which dates throughout history.  The oldest piece on display is a very rare bayonet from the Revolutionary War.


The M3 began replacing the Thompson in the front-line service from late 1944 to early 1945.  However, both the M3 and its variant (M3A1) saw very little combat during WWII due to production problems.



The M3 design emerged when the US Army Ordnance Board began observing the effectiveness of submachine guns used in Western Europe.  They had a particular interest in the German 9mm MP40 and British Sten guns.  In October of 1942, they began looking into developing their own submachine gun based on the Sten.  They had the US Army – as well as their Infantry and Cavalry branches – submit requirements for an automatic or semi-automatic, shoulder-fire weapon with either a .45 ACP or .30 Carbine caliber.    The lists were reviewed and some modifications were made.  The modification called for the gun to be constructed from a single sheet of metal in a .45 ACP caliber.  These changes allowed for faster, inexpensive production requiring a minimal amount of machinery.



  • US Service History:  1942 to 1992
  • Production History:  1943 to 1945
  • Total Built:  Approximately 700,000
  • Cartridge:  .45 ACP
    • 9x19mm Parabellum
    • Action:  Blowback, open bolt
    • Firing rate:  450 rounds per minute (cyclic)
    • Muzzle Velocity:  920 feet per second
    • Range:  Effective at 100 yards with fixed sights

The M3 was used throughout a number of conflicts including World War II, the Korean War, the Bay of Pigs Invasion and the Vietnam War.  Though no longer in US service, the M3 was revived in 2004 and continues to be used in the Philippines.  Throughout its history, a dozen different countries utilized the United States M3 submachine gun or one of its variants.