M3 Grease Gun
Encyclopedia : M : M3 : M3G : M3 Grease Gun
 M3A1 with stock extended from [Modern Firearms]'' | |
| M3 "Grease Gun" | |
|---|---|
| Type | Submachine gun |
| Nation(s) of origin | United States of America |
| Era | World War II |
| History | |
| Date of design | 1942 |
| Production period | 1942— |
| Service duration | 1942–1994 |
| Operators | Philippines, United States |
| War service | WWII, Korea, Vietnam, Desert Storm (limited) |
| Variants | M3, M3A1 |
| Number built | 680,000 approx. |
| Specifications | |
| Type | Submachine gun |
| Caliber | .45 ACP (11 mm), 9 mm |
| Ammunition | .45 ACP, 9 x 19 mm |
| Feed system | 30-round detachable box magazine |
| Firearm action>Action | Blowback |
| Length | 570 mm (22.4 in), stock retracted; 745 mm (29.3 in), stock extended |
| Gun barrel>Barrel length | 203 mm (8 in) |
| Weight | 3.7 kg (8.16 lb) |
| Rate of fire | 450 round/min |
| Muzzle velocity | 280 m/s (920 ft/s) |
| Effective range | ~50 m (54.7 yd) |
The M3 "Grease Gun" (more formally United States Submachine Gun, Cal. .45, M3/M3A1) was a submachine gun developed by the United States during World War II as a cheaper substitute for the Thompson. It was nicknamed the Grease Gun because of its resemblance to an automotive grease gun.
History and design
When World War II began, the Thompson submachine gun was the standard U.S. submachine gun. However, the Thompson was comparatively expensive in terms of machining and time to manufacture. Newer Thompson models cost less to manufacture (e.g. the M1928 vs. the M1A1), but a brand new design was required to be produced much more economically. The basic concept of a crude, cheaper, mass-produced firearm traces back to the Chauchat of World War I, the most produced machine gun of that war. The .45 caliber M3 was introduced in 1942, designed specifically for simplified production using stamped metal parts. Similar reduced manufacturing costs for a submachine gun design was undertaken by the British (Lanchester to the Sten), Germany (MP34, MP38 to MP40), and others. The Soviet Union, France and Italy would also make inexpensive submachine gun designs in the 1940s.
Far easier to manufacture than the Thompson, the M3 incorporated several updated design features. A low cyclical rate of fire and the straight line of recoil thrust made it easier to control than other submachine guns, especially during automatic fire. In contrast to the relatively well-built Thompson, the M3's simplicity and generous clearances made it far more reliable under the adverse conditions encountered at the fighting front. When the M3 was adopted as a standard weapon, the Thompson was categorized as a "Limited Standard" or "Substitute Standard" submachine gun.
The gun was made by welding two pressed-metal shells together to form the exterior of the weapon. The barrel was held on by a simple nut and the bolt traveled on two guide rods inside the receiver. This provided clearance between the bolt and receiver, keeping foreign matter from jamming the weapon. The major weak point of the Grease Gun was its magazine. Unlike the Thompson magazines that fed from two sides of the magazine, the Grease Gun fed from a single position. This meant that cartridges in the double-column magazine had to merge to the feeding position. As a result, the magazine was sensitive to dirt and debris.
The M3 used the blowback method of operation. It could be fired only in fully-automatic mode, but experienced soldiers could usually fire single shots with it. In its original version, the weapon fired the .45 ACP cartridge (the same one used by the Thompson and the Colt M1911 pistol) from a 30-round detachable box-type magazine. Before firing, the ejection port had to be opened manually by the operator; this also functioned as the weapon's safety. An oiler is contained in the weapon's pistol grip. The stock doubles as the wrench for the barrel nut, a screwdriver, the cleaning rod, and as a magazine loading tool.
The M3 and M3A1 served through the Korean War and the Vietnam War. They remained in limited use with U.S. military into the 1990s, to include service in the 1991 Gulf War (e.g. drivers in the 19th Engineer Battalion, which was attached to the U.S. 1st Armored Division, deployed with the M3A1 as an alternate arm) and as defensive weapon for the crews of M88A1 ARV, until replaced by the M4 Carbine.
The Philippine Marine Corps currently uses the M3 as personal defense weapons for armor crews and has issued locally modified sound and flash suppressed versions to their special operations units.
Variants
T20
Experimental designation of what was type-classified as the M3. Development of the T15 project.M3
- Entered service December 1942;
- Designed specifically as a low-cost substitute for the Thompson submachine gun. Production at General Motors automobile parts plants was simplified by making use of stamped metal and only a little machining. A number of deficiencies were found during the initial two years of use. Combat introduction in time for use in Normandy (June 1944) was delayed until the deficiencies were corrected. However, continuing doubts about its reliability made it unpopular among troops.
M3A1
- Entered service December 1944;
- The A1 model corrected the faults of the earlier version. New features included a larger ejection port, a stronger cover spring, and a change to the cocking method. The original M3 was cocked by a crank-like lever. On the M3A1, the bolt had a machined recess which was exposed when the ejection port cover was opened. The user had to insert a finger in said recess to pull the bolt back to the cocked position. It could be adapted to fire the 9 mm Parabellum round by changing the barrel and bolt, and an adapter permitted the use of the magazine from the British Sten gun or the German MP40.
See also
- List of submachine guns
- List of World War II firearms
- List of individual weapons of the U.S. Armed Forces
External links
- [Small Arms Review: The M3A1 Grease Gun]
- [M-3 Submachine Gun]
- [Modern Firearms: M3 and M3A1]
- [Philippine Marine Corps M3 SpecOps Gen 2]
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