It really doesn't take much of a spin to stabilize a ball and given the same bore smoothness, the slower the twist and deeper the groove,, (with in reason) the less fouling one has to contend with.
I made a .54 cal horse pistol many years ago with a cut off rifle barrel 9 inches long with a pitch of 1in 60 and out to the 50 yards tested it is remarkably accurate. No one I'm aware of would purposely make a pistol with that slow of pitch but I wanted to see if it would work and it surely did. It changed what I though I knew about how fast a round ball needs to spin to be accurate, at least to the 50 yard mark it has been tested to.