Hey cfx I've been pondering the same thing and what i thought i'd try is a .45(sam yang 909) sabot for blackpowder muzzleloaders as the shot cup, lined with thin rice paper rolled inside the sabot to keep the shot from falling through the petals, cardboard wad to keep the shot from rolling out the barrel. The only pistol shotshells i've ever seen still had a metallic shell casing right? Expand on your idea if you don't mind? Jeff