as I understand your problem your only chance is a patched bullet. when we think you set the powderload, a wad, say something from cycleflywads, and the bullet. the bullet, if it be a conical minie can't realy work with a wad over the powdercharge. A fullsize conical isn't practical to load but a short undersize conical bullet with the rigth patcht is the technical solution for this problem.I believe a patched bullet will allways stand the force of the first shot in a double.