Originally Posted by
Der Gebirgsjager
I'm a bit lost and mystified here. Isn't that why plastic wads with shot cups were invented? And if you have to go really retro, then consider black powder shotguns where the powder is dumped down the bore followed by a measure of shot and sometimes a thin wad to hold it in. Before shot cups all barrels had streaks, and a little cleaning solved the problem. Other than the streaking, lead shot won't hurt the bore, and if you're using steel shot I wouldn't bet on Mylar protecting sufficiently to avoid damage. I'd go with the shot cup wads.
DG