The MP5 or the Heckler & Koch MP5 is a submachine gun used by the Hellsing Agency Special Military Forces.
Information
Heckler & Koch, encouraged by the success of the G3 automatic rifle, developed a family of small arms consisting of four types of firearms all based on a common G3 design layout and operating principle. The first type was chambered for 7.62×51mm NATO, the second for the 7.62×39mm M43 round, the third for the intermediate 5.56×45mm NATO caliber, and the fourth type for the 9×19mm Parabellum pistol cartridge.
Hellsing
In Hellsing, the Hellsing soldiers primarily uses this as their main weapon, as their armors are probably heavy and this submachine gun is quite perfect for that. This submachine-gun was also used by the Hellsing trainees in the anime, known as the group of Atheists and Heathens.