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 iron sights consists 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 mounting accessories such as optical sights, tactical lights, or laser sights. Vertical foregrips can be attached to the bottom rail for better control during burst and automatic fire. Variants The UMP is interchangeable between three different calibres: The UMP45, chambered in .45 ACP The UMP40, chambered in .40 S&W The UMP9, chambered in 9×19mm Parabellum Apart from the different chambering, all versions feature the same design model, the exterior differences being the curved magazine used on the UMP9, while both the UMP40 and UMP45 each use a straight magazine. All three versions of the weapon can be cross-converted to any of the round chamberings via replacing the bolt, barrel, and magazine. The USC or Universal Self-loading Carbine is a semi-automatic variant of the UMP designed for civilian use. It was created 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. Originally available in gray, as of 2008 the USC came only in an all-black finish. Production of the USC was halted in 2013. In 2018 H&K announced a limited production run of new USC rifles. Recall In 2000, H&K recalled certain UMP and USC serial numbers due to faulty operating handles. The faulty handles, made of polymer, could break off, making the weapons inoperable. Users References External links 2008 Heckler & Koch Military and LE brochure Nazarian's Gun Recognition Guide – H&K UMP Demonstration (MOV) The UMP at Modern Firearms UMP Post–Cold War weapons of Germany .45 ACP submachine guns .40 S&W submachine guns 9mm Parabellum submachine guns Police weapons Weapons and ammunition introduced in 2000