I don't know about the round balls in the cartridges, but I do know my quick twist inline will shoot patched balls quite well if the velocity is backed off. You 'd likely be better off to look at some of the extreme lightwieght wadcutter moulds that are available from ballisticast if you want to spend the cake to persue this idea. They have them in all the calibers you mentioned I think. You could buy one mould with all of them in it, but it would be a pricey mould. These are projectiles that I believe where intended to shoot 2 or 3 to the cartridge, I seem to remember reading an article with these quite a few years ago. These have lube grooves in them, so the leading problem associated with shooting an unlubed, or innefectivley lubed ball that does not neccesarily fit your bore may be reduced or negated altogether. If you hunt around, you may be able to find other mould mfg's who have some of these available, as the solution I suggested would cost you about two bills for a three cavity mould with one of each caliber in it. I would suggest using a charge of bulleye or 231 or No2 that is listed for a light cast bullet and working your way down for something like this. You might be better seved by using wax bullets like the old time trick shooters used, depending on how far away those squirrels are. Cheaper than the mould would be a 22 revolver, like a Taurus, shooting CB caps or 22 shorts. I've shot a couple of these and I suspect the accuracy would be on par with, or superior to, the loads put together with the expensive moulds and a bunch of load development.