I`m probably wrong but the Beeman p1 looks a little like Alucard`s 13MM Jackal.
Here`s some info on it
The Weihrauch HW45 is an air pistol manufactured by Weihrauch & Weihrauch. It is more commonly known in North America as the Beeman P-1.
The Pistol is described as a sporter and is available in three different calibres: .177, .20 and .22. The HW45 is used for target shooting, plinking (a slang term for 'fun shooting' and dispatching small rodents. Its design is based on the cartridge pistol M1911, except that it has a greatly enlarged slide to accommodate the powerplant.
The HW45 has a self-contained powerplant in the form of a compressed spring. The compression is achieved via an over arm cocking lever incorporated into the barrel. The HW45 features a Precision adjustable two stage trigger and a micrometer rear sight adjustable for windage and elevation. There is also a grooved dovetail rail for accessories.
Alucard and Hellsing are (c) Kohta hirano