How about pumpguns?
I never heard of any for the few mag-fed leverguns, but Remington pumpguns atke mags, and I know that at least 10-rounders have been made. I think it would be an interesting project to at least check into the feasability of doing an end-to-end modification. I once ( about 14 years ago ) made a 45-round carbine mag out of a 15 rounder soft-soldered to the underside of a 30 rounder. I worked just fine, but was so long as to be of no practical use. The only tricky part was joining the springs with little crimpons.
crankshaft
paranoia is just fine when THEY really, truly ARE out to get You!