United Defense M42
|United Defense M42|
UD M42 submachine gun
|Place of origin||United States|
|Used by||See Users|
|Wars||World War II|
|Designer||Carl G. Swebilius|
|Manufacturer||United Defense Supply Corp.|
|Weight||10 lbs., (4.1 kg)|
|Length||32.3 in. (820 mm)|
|Barrel length||11 in. (279 mm)|
.45 ACP (Prototype model)
|Rate of fire||700 rpm|
|Muzzle velocity||1,100 ft/s (335.3 m/s)|
|Feed system||25-round box magazine (also issued with two 25-round magazines welded face-to-face)|
|Sights||fixed front post, rear adjustable for windage|
The United Defense M42, sometimes known as the Marlin for the manufacturer, was an American submachine gun in World War II. It was produced from 1942 to 1943 by United Defense Supply Corp. (a government-formed company specifically tasked with weapons development) for possible issue as a replacement for the Thompson submachine gun and was used by agents of the Office of Strategic Services (OSS).
The M42 was developed by United Defense Supply Corporation specifically as a replacement for the Thompson submachine gun, which the U.S. military considered both expensive and complicated to produce. Made in both 9×19mm Parabellum and .45 ACP prototypes, the 9 mm version was the only one to ever see widespread production. Manufactured by High Standard Firearms and Marlin Firearms, about 15,000 were produced in the last three years of World War II. Only six .45 ACP prototype test guns were made.
The weapon holds 25 9mm rounds in its magazine (designed by John E. Owsley, covered by patent 2,289,067). It has a cyclic rate of 700 rounds per minute. Frequently two 25-round magazines were welded face-to-face allowing a quick reload when the first became empty (see illustration). The weapon itself weighs 10 lb (4.54 kg)(empty), with a length of 32.3 in (820 mm). The barrel length is 11 in (279 mm), and it has six-groove right-hand rifling.
An extremely simple design, it was a straight blowback, selective fire weapon. It was built under "hurry-up" war conditions and some of its design flaws stem from this approach. Problems with the weapon were varied. Under combat conditions it was found that the sheet metal magazines had a tendency to warp out of shape causing feeding problems. They had little tolerance for exposure to large amounts of mud and sand and tended to jam if not cleaned regularly. The gun was also labor-intensive to produce. It used all machined parts, no stampings, and under wartime conditions machine work is at a premium. However, proving ground tests showed it was easier to strip and maintain than the Thompson or Sten Mark II and was more accurate at 100 yards. Despite its expense and precision, the UD42 enjoyed a good reputation in OSS usage.
The M42 submachine gun was classified as a substitute standard when the M3 submachine gun was introduced. It is often stated that it used 20-round magazines, which were used in .45-caliber prototypes. Only 25-round magazines were used in the 9mm. United Defense Supply Corporation (1940-45) was a government-formed company producing, acquiring, carrying, and selling arms, equipment, strategic and critical materials and supplies, and land. “United” was not actually part of its title. The M42 SMG was actually developed at High Standard Firearms and manufactured by Marlin Firearms Company.
Intended for use by U.S. troops at the time of its design, it found more favor being air-dropped to partisan forces in occupied Europe. The weapon was air dropped to supply British-led partisan forces on the island of Crete, where it was used extensively. It also saw use among the partisan forces of the Italian and French Resistance. Some of them were transferred to Dai Li's regular resistance forces in China for use against the Japanese invasion. The United Defense M42 was issued for use by Filipino troops under the Philippine Army and Philippine Constabulary during World War II from 1942 through the Post-World War II era until the 1960s and was used by the local recognized guerrillas from 1942 to 1945 during the Japanese Occupation. The use of the 9 mm caliber allowed resistance forces to use captured ammunition in their weapons, eliminating the need for repeated re-supply drops.
Overall the weapon failed in its intended role (to replace the Thompson) but proved effective in limited use in the hands of resistance forces.
- Republic of China
- Italy (1943–45)
- Philippines used by the Philippine Army and Constabulary during World War II and Post War era from 1942 to 1960s and using again by the local recognized guerrillas from 1942 to 1945 during World War II.
- United States
- Czechoslovakia 100 pieces from US supplies used by insurgent army and partisans during Slovak National Uprising
- Nelson, Thomas B. (1963). The World's Submachine Guns, Volume I. International Small Arms Publishers.
- Iannamico, Frank. (2004). United States Submachine Guns: From the American 180 to the ZX-7. Moose Lake Publishing. ISBN 0-9742724-0-X.
- Brophy, William S. (1989). Marlin Firearms: A History of the Guns and the Company That Made Them. Stackpole Books.
- Bishop, Chris (1998). The Encyclopedia of Weapons of World War II. New York: Orbis Publishing Ltd. ISBN 0-7607-1022-8.
- Canfield, Bruce N. (2006). "M42 UD (United Defense) Submachine Gun". American Rifleman. National Rifle Association. 154 (September): 26&27.
- McNab, Chris (2002). 20th Century Military Uniforms (2nd ed.). Kent: Grange Books. ISBN 1-84013-476-3.