The Remington XP-100 (from eXperimental Pistol number 100) is a bolt-action pistol produced by Remington Arms from 1963 to 1998.
In 1979, XP-100 pistols and Remington Model 600 rifles were recalled because of a safety issue. The bolt was fully locked when the safety was on, making it impossible to unload the gun with the safety on. Remington made a free modification available that allowed the bolt to open while the gun was on safe, allowing it to be unloaded while the gun was still on safe.
Custom modified double pistol grips:
It being a bull pup gives it better balance. Otherwise it’d be front heavy. It’s a bolt action pistol because it was made for for hunting varmints and competitive handgun shooting.