You may have been using the wrong stuff as we never had a ball break up in flight and if we didn't hit anything too hard we could re use them. I will check the sack of mix and get the right brand. As to bore wear, after 25 rounds I noticed so light polishing, but no measurable wear, but we shot ours with a centering base wad made from scrap 1/4" ply and masking tape.
Since I have a Fur Trade cannon I don't shoot cats I use Ground squirrels. If you use a corn trail they load themselves and the fur keeps the bore clean between shots. They are also good for shooting AT cats.