don't like pistol as a description, then use handgun.
what do you get when you put a rifled barrel on your 500 mossburg shotgun?

rifle- A rifle is a firearm designed to be fired from the shoulder, with a barrel that has a helical groove or pattern of grooves ("rifling") cut into the barrel walls.

shotgun-A shotgun (also known as a scattergun and peppergun,[1] or historically as a fowling piece) is a firearm that is usually designed to be fired from the shoulder, which uses the energy of a fixed shell to fire a number of small spherical pellets called shot, or a solid projectile called a slug.

pistol - When distinguished as a subset of handguns, a pistol is a handgun with a chamber that is integral with the barrel, as opposed to a revolver, wherein the chamber is separate from the barrel as a revolving cylinder.

handgun - A handgun is a firearm designed to be held and operated by one hand. This characteristic differentiates handguns as a general class of firearms from long guns such as rifles and shotguns (which are mounted against the shoulder).