This is one big looking bad ass gun.
This is the iconic pistol from the Hellsing anime series. This iconic pistol for Fallout 4 is called The Jackal. You can find and download the mod from 3DM Game at the link listed below.
jinjin1221aaa deserves credit for the release of this mod on the 3DM Game website. However, DMagnus is the one who deserves credit for the creation of this mod. The link to the original mod creator's mod is at the link below.