The UMP family ("Universale Maschinenpistole" or "Universal Machine Pistol") is a series of submachine guns designed by the German firm of Heckler & Koch in the 1990s as a successor to the excellent world renowned HK MP5 series. The HK UMP entered production in 1999 and is still being manufactured today. She has become the staple of several specialized military organizations found throughout the world that include US Customs and Border Protection, the Royal Thai Navy SEALs and the Jordanian Special Operations Forces.
The HK UMP comes in three distinct variants - the UMP9, the UMP40 and the UMP45. Each UMP designation signifies the caliber of the cartridge. As such, the UMP is chambered to fire the 9x19mm Parabellum while the UMP40 is chambered for the .40 Smith & Wesson (.40 S&W). Likewise, the UMP45 is chambered to fire the .45 ACP cartridge. This is a departure from the original HK MP5 series which was limited to firing just the 9mm Parabellum submachine gun round. Despite the different cartridges, each model is essentially the same Heckler & Koch submachine gun with the magazine being the ultimate identifier. All three versions share a commonality of parts but changes to the barrel, bolt and - of course - the magazine - are required to have the base UMP fire a different cartridge.
As each cartridge varies in size, the UMP family makes use of two different magazine lengths - the UMP40 and UMP9 both feed from a 30-round detachable box while the UMP45 is limited to a 25-round detachable box. Of note is that the UMP40 and UMP45 utilized a straight magazine and the UMP9 makes use of a curved magazine. The operating action for all three systems is blowback from a closed bolt. A rate-if-fire of 650 rounds per minute is listed though the UMP45 is closer to 600 rounds per minute. While this rate-of-fire is somewhat lower than perhaps some of her contemporaries, it results in notably longer effective ranges and provides a weapon that can double as both a close-quarters submachine gun and an "assault" style rifle to an extent. Use of the 9x19 Parabellum cartridge allows for accessible ranges out to 100 meters while the .45 ACP does most of its damage at ranges within 50 meters. The UMP family features a semi-automatic, 2-round burst and full automatic firing modes with the HK-standard, clearly-marked selector switch placed conveniently near the pistol grip along the left side of the receiver. The curved trigger system sits within an angular guard that is large enough to accept a gloved finger. The cocking handle is set to the forward left side of the weapon, above the forend. Spent shell casings are ejected through a rectangular port along the right side of the receiver, this above the magazine feed. Sighting is integrated via a vertical front post/ring and a rear-set aperture device. The UMP is Picatinny-rail capable and can support various sights, lights, grips and other accessories across the top and sides of the receiver and under the forend ahead of the magazine feed.
The UMP is constructed largely of polymers to help combat environmental corrosion and also serves to keep the overall weight of the system down to manageable levels. The weapon weights in at just 4.6lbs (UMP9, UMP40) and 5lbs (UMP45) without the magazine installed - making her lighter than the preceding HK MP5 series. All forms share a running length of 27.2 inches (690mm) with the skeletal stock fully extended and can collapse to be 17.7 inches (450mm) with the stock folded over the right side of the receiver. This makes her a relatively compact weapon for use by all types of light infantry or close-quarters combatants. Barrel length measures in at 8 inches (200mm) and a flash suppressor is fitted over the muzzle.
The UMP series has since increased in popularity across the globe with the UMP9 and UMP40 forms seemingly taking precedence. Currently, notable operators include Australian special forces, Jordanian special forces, the Latvian Army, marine forces of Mexico, Romanian special forces, Serbian special forces, Slovakian special forces, Thai Navy SEALs and both the US Customs and Border Protection and Pentagon Force Protection agencies - the latter two making use of the UMP40 model version.
The USC (Universal Self-Loading Carbine) is a commercial version of the UMP family line. This sporting version of the militarized weapon first appeared after 1994 to follow the standards of the imposed US "Assault Weapons Ban". There are only subtle differences in the USC versus the military UMP and include a semi-automatic-only trigger action, a noticeably longer barrel sans the flash suppressor, a revised fixed stock (now made skeletal with a connected pistol grip and large open "thumb" hole area) and a 10-round straight magazine. The USC has been made available in a mixed light gray/black color combo or complete dark black finish to expand commercial market tastes.