Shoot it first and see how it does. I've got a few black powder guns here that are on the other side of a hundred years old whose barrels look pretty sketchy, but you'd be surprised what just a hint of rifling in that pitting will do to stabilize a bullet. The only gun that I've been tempted to sleeve is a Winchester 1906 that was converted from .22 shorts to .22s/l/lr, but shot with corrosive shorts. It eroded the chamber to the point that the brass won't extract because the case mouth is expanded too far. But it's still quite accurate.
Well we don't rent pigs and I figure it's better to say it right out front because a man that does like to rent pigs is... he's hard to stop - Gus McCrae