The M3 was an American .45-caliber submachine gun adopted for U.S. Army service on 12 December 1942, as the United States Submachine Gun, Cal. .45, M3. Compared to the Thompson submachine gun, the M3 was cheaper to produce, lighter, more accurate, and was also chambered in .45 ACP. The M3 was commonly referred to as the "Grease Gun" or simply "the Greaser," owing to its visual similarity to the mechanic's tool.

Intended as a replacement for the .45-caliber Thompson series of submachine guns, the M3 and its improved successor, the M3A1 began to replace the Thompson in first-line service in late 1944 and early 1945. Due to delays caused by production issues and approved specification changes, the M3/M3A1 saw relatively little combat use in World War II.

The M3 was an automatic, air-cooled blowback-operated weapon that fired from an open bolt. Constructed of plain .060-in. thick sheet steel, the M3 receiver was stamped in two halves that were then welded together. The M3 was striker-fired, with a fixed firing pin contained inside the bolt. The bolt was drilled longitudinally to support two parallel guide rods, upon which were mounted twin return (recoil) springs. This configuration allowed for larger machining tolerances while providing operating clearance in the event of dust, sand, or mud ingress. The M3 featured a spring-loaded extractor which was housed inside the bolt head, while the ejector was located in the trigger group. Like the British Sten, time and expense was saved by cold-swaging the M3's barrel.

In Project Reality, the M3A1 appears in Project Reality: Normandy, Project Reality: Vietnam, and Project Reality: Falklands. It only features one firing mode, fully automatic.


  • M3A1
    • .45 ACP
    • Original design
    • Used by USA(1940), USA(Vietnam), USMC(Vietnam)
  • PAM1
    • Domestic Argentinian Copy
    • 9x19mm 
    • Used by Argentina(1980)



  • The M3A1 has 2 different animations, one for PR:N and PR:V, and another for PR:F. The M3A1's animations will be updated to the newer one found in PR:F in future releases. 
  • The M3 and M3A1 both erroneously ejects rifle cartridges instead of the .45 ACP that they actually fire.

See alsoEdit

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