United Defense UD M42
Marlin Firearms (for United Defense Supply Corp) · Submachine Gun · Discontinued · 1942
Also known as: UD-42, UD M.'42, Marlin UD42, Model UD of 1941
Overview
The United Defense UD M42 was an American 9mm submachine gun designed by Carl Swebilius and manufactured by Marlin Firearms under contract to the United Defense Supply Corporation. Originally ordered for the Dutch East Indies in 1942, it never displaced the M1 Thompson in US service and instead became closely associated with the OSS, which air-dropped large numbers to resistance and partisan forces across occupied Europe. It was a well-made, blowback, open-bolt weapon feeding from paired 20-round box magazines, but its tight tolerances made it sensitive to battlefield dirt.
Specifications
| Weight (empty) | 4100 g (144.6 oz) |
| Overall Length | 820 mm (32.28") |
| Barrel Length | 279 mm (10.98") |
| Action Type | Blowback |
| Firing Mechanism | Hammer Fired |
| Trigger Type | Single Stage |
| Magazine Capacity | 20 rounds |
| Magazine Type | Detachable Box |
| Muzzle Velocity | 335 m/s (1099 fps) |
| Effective Range | 150 m (164 yd) |
| Rate of Fire | 700 rpm |
| Barrel Rifling | Right Hand |
| Frame Material | Steel |
| Barrel Material | Steel |
| Stock Material | Wood |
| Finish | Blued |
Calibers
- 9x19mm Parabellum · primary · 9mm NATO — also known as 9mm Luger, 9mm NATO, 9x19mm
Features
- Firing modes: Semi Automatic, Full Automatic
- Feed systems: Detachable Box Magazine
- Safety mechanisms: Manual Safety
- Features: Open Bolt, Paired Box Magazines, Wooden Shoulder Stock, Side Charging Handle
Service history
Operators
- United States Office of Strategic Services · adopted 1942 · as UD M.'42
- Netherlands (Dutch East Indies order) · adopted 1942
- French Resistance · adopted 1944
Conflicts
- World War II (1939-1945)
Production
Estimated total produced: 15,000 · Production years: 1942-1943
Initial Netherlands order ~7,500 plus further production; failed to displace the Thompson in US service
Origin
Country of origin: United States
Designer: Carl G. Swebilius
Discontinued: 1943
Notes
Sources disagree on per-magazine capacity (20 vs 25 rounds); 20 is the better-supported figure. The paired front-to-back magazines allowed rapid reloading but were prone to warping.
Background
Around 2,400 UD M42s were parachuted into France in 1944 to arm the resistance, and by Allied accounts a large share were promptly captured by the Germans, making the gun a quiet icon of clandestine OSS operations rather than a frontline US weapon.