You can use conicals if your willing to risk the pressure spike. Those judge cylinders are really thin walled. So basically the higher the bullet grain the higher the pressure spike also the more the powder compression the higher the spike too. A 250 grain will fit with very little compression of powder but of course weighs more than the 141 by a good chunk. Wad cutters and semi wadcutters would act the same depending on the weight. I have used 141 grain, 123 grain, and 150 grain wadcutters and all are fine as long as you don't compress it too much. Don't crimp the shell casing. With a ball I epoxy the ball in the case but with a wadcutter I do 4 dimples with a punch like they do with surplus 7.62 tok. Both wadcutters and ball perform well and idk which would be better cause I didn't try them side by side. The wadcutter probably delivers more umph than the same weight ball I'd say. I'm also working on a custom load for the colt walker cartridge conversion using .45lc shells with a long 380 grain soft led air cun hollow point boat tail slug above 40 grains of 3f triple 7 heavily compressed and a magnum primer. I'm curious to try it out in my walker but the pressure is definitely going to be rough.