The Heckler & Koch UMP (Universale Maschinenpistole, German for "Universal Submachine Gun") is a submachine gun developed and manufactured by Heckler & Koch. The UMP has been adopted by various agencies such as the U.S. Customs and Border Protection.^[3] Heckler & Koch developed the UMP as a lighter and cheaper successor to the MP5, though both remain in production.^[4]

The UMP is a Blowback operated, magazine-fed submachine gun firing from a closed bolt.^[5]

As originally designed, the UMP is chambered for larger cartridges (.45 ACP and .40 S&W) than other submachine guns like the MP5, to provide more stopping power against unarmored targets (with slightly lower effectiveness at longer range) than the MP5 (largely offered in 9×19mm, albeit with short-lived production of 10mm Auto and .40 S&W variants). A larger cartridge produces more recoil, and makes it more difficult to control in fully automatic firing. To mitigate this, the cyclic rate of fire was reduced to around 600–745 rounds per minute (RPM) for the UMP40^[6] and 600 rounds per minute for the UMP45, which makes it one of the slower firing submachine guns on the market.^[5]

The UMP9 (the 9×19mm version of the UMP) is almost 0.2 kilograms (0.44 lb) lighter than its MP5 counterpart. Its predominantly polymer construction reduces both its weight and the number of parts susceptible to corrosion.^[5][7] It has a cyclic rate of fire of around 600–650 rounds per minute.

The UMP is available in four trigger group configurations, featuring different combinations of semi-automatic, 2-round burst, fully automatic, and safe settings. It features a side-folding buttstock to reduce its length during transport. When the last round of the UMP is fired, the bolt locks open, and can be released via a catch on the left side. The standard viewing sights are composed of an aperture rear sight and a front ring with a vertical post. It can mount four Picatinny rails (one on top of the receiver, and one on the right, left, and the bottom of the handguard) for the attachment of accessories such as optical sights, flashlights, or laser sights. Vertical fore-grips can be attached to the bottom rail for increased control during burst and automatic fire.^[5]

There are three variants of the UMP:

Apart from the different chambering, all versions feature the same basic design, the most noticeable difference being the curved magazine used on the UMP9, while the UMP40 and UMP45 use a straight magazines. All three versions of the weapon can be converted to any of the available chamberings via replacement of the bolt, barrel, and magazine.^[5][7]

The USC or Universal Self-loading Carbine is a semi-automatic variant of the UMP for private citizens. It was designed following the Assault Weapons Ban of 1994 in the United States and was introduced in 2000. Changes from the original UMP include a "thumbhole" type stock/grip instead of the pistol grip of the UMP, a longer barrel without the flash suppressor, a magazine limited to 10 rounds, and a semi-automatic-only trigger group and action.^[8] Originally available in gray, as of 2008 the USC came only in an all-black finish.^[9] Production of the USC was halted in 2013.^[10] In 2018 H&K announced a limited production run of new USC rifles.

In 2000, H&K recalled certain UMP and USC serial numbers due to faulty operating handles. The faulty handles, made of a polymer, could break off making the weapons inoperable.^[11]