Paintballs would break. No question about it.
Burnt Latke, I believe, mentions when he tried to reuse the bb's from his strafer, that the used bb's were slightly out of round, in other words, they didnt fit the barrel after being shot.
If metal bb's can be dented or what not by this contraption,
gelatin paintballs will be destroyed. I promise you.
Try it out if you like, but my vote is that the paintballs will break inside of it, i doubt many make it out of the barrel.