Would it work to simply patch the slug with a denim cloth patch of around 30-32 thousandts like a patched round ball in a muzzleloader? That would fill the void and keep the slug tight in the brass shell for accuracy. Might want to lube the patch and make sure the patched slug will go down the bore before shooting it!
EDIT: Thought again about this, and if this is a rifled bore situation then naturally it's not going to work. Initially thought it was a "slug down a smoothbore" situation, and if this is the case then it might work after first making sure the patched slug will pass down the bore.
Last edited by woodsrunner38; 07/07/10 07:27 AM.