Can you put a 30->22 sabot into a .30 Carbine cartridge? Then again, if you did that, could you shoot in in your .30 Carbine Blackhawk SA revolver, or would the cylinder gap snag the sabot?
So far as 45 sabots: have you checked to see if there are any sabots for .45 blackpowder muzzleloaders that might launch a .357 bullet?