UMP45

 The UMP is a blowback-operated, magazine-fed submachine gun firing from a closed bolt. As originally designed, the UMP is chambered for larger cartridges than other submachine guns like the MP5, to provide more stopping power against unarmored targets (with a slightly lower effective range) than the 9x19mm MP5 provides. A larger cartridge produces more recoil, and makes control more difficult in fully automatic firing. To mitigate this, the cyclic rate of fire was reduced to 650 rounds/min (600 rounds/min for the UMP45), which makes it one of the slower firing submachine guns on the market.

The UMP9 (the 9x19mm version of the UMP) is almost 0.45 kg (almost 1 lb) lighter than its MP5 counterpart. Its predominantly polymer construction reduces both its weight and the number of parts susceptible to corrosion. These polymers stand up well to wear and tear in the field.

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 comprise 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 foregrips can be attached to the bottom rail for increased controllability during burst and automatic fire.