For a single shot slug or ball gun, I would try and skip any case resize or crimping. The projectile could be held in place with hot wax. I even heard of hot glue, but do not know about that. The case would be filled with powder and wads or some filler.
This is a little off topic for this thread. You might look for some black powder cartridge relaoding & shooting forum. That is even though you are apparently not planning to load black powder.
