The United Defense UD M42 SMG 9mm is a usa-made select-fire submachine gun chambered in 9mm Luger, introduced in 1942. Primary use: military. Type: Submachine Gun Action: Select-Fire Caliber: 9mm Luger Capacity: 25 Year introduced: 1942, USA Weight: 88 oz Overall length: 24" Status: Discontinued Military use: Yes Intended use: military