When I was using paper "cartridge" shot loads I would make a seperate internal tube for the shot out of wax paper (I used to do this for the powder on paper cartridges used for hunting - where there was a chance it night get damp). No more than two wraps thick. If you use a dowel narrower than the bore there will be no doubt that the wax paper will tear when the charge is packed down. When I assembled the loads I would make seperate "cartridges": one for the powder and the over powder wad, and a seperate one with the shot UNDER the cushion wad (pre-lubed) and over-powder wad. To load (I had a 24 hole belly box - so I could carry 12 shots) pull the powder squid, bite off the end and pour in the powder, fish out the over powder card and seat it, pocketing the paper tube. Then, grab a shot 'cartridge', bite off the end, squeeze the tube until the fiber wad is loose, set this in and ram it down while palming the shot roll. Then, drop in the shot roll and pack it down (still in the wax paper cylinder) and set the over shot card over that. My musket used to throw these in about three feet at 25 yards, which was just perfect. I think the wax paper was more frangible (I've been saving that word for years) and I never found evidence of it holding together past the muzzle. For additional spread, jamb the paper wrappers on top of the over-shot card.