Slugging .32-20 and 9.3 barrels

Too big is not a problem, in my experience. If you have round balls that are pure lead, and large enough, then use those.

If the round balls are too small to get a good impression of the rifling, set them on something hard and give a gentle whack with a hammer. They'll upset a fair amount with little effort.

Good luck.

Go to the next larger egg. Round balls tend to try to roll if the fit is too close, so they can chatter down the bore. I find it easiest to start with an oversize ball and run it through a sizer to get it close before slugging with it. That prevents chatter. Lee has a .314" sizer that should form an oversize slug close to size for you. If you don't have the sizer, though, just try to form it by tapping it into the bore with a short length of dowel. You can also upset a ball as Mike described. You can also start a ball into the bore and lay a 1/4" brass rod in there and tap it with a shorter piece from the same rod from the other side. The sandwiched ball will bump up. This really is not critical. Be sure to use a light coat of oil.

You want the bell sinker to be larger than the bore - even one greatly oversize is better than too small. Grease the bore and sinker liberally and insert pointy end in bore muzzle. Use a non-metallic rod (wood, plastic) with a blunt end to start the slug down the bore. Once the rifling has engraved it, it will slide easier and you can push it to the chamber with a blunt tipped cleaning rod.

Thank you, gentlemen. That's all I need to know (for now).