Having 32" choked barrels, I'd shorten them to 28" to get rid of the chokes. Better yet would be finding a barrel maker who could rifle the chokes, would turn it into an 8 bore paradox. Something on the order of 60" to 80" of twist would be about right for round balls and would still give strong Imp Cylinder patterns with shot. Something to think about.

You could shorten the tubes to just after the choke started, leaving about .010" constriction. That would shoot well with shot and still allow an .800" round ball (about 775gr. in pure lead) held in a hollowed wad for centering. I'd start around 150gr. 2F black powder and go from there. Probably run upwards of 273gr. for a 'good' 10 dram load with round ball, but 8 drams (218gr.) is probably about the limit for recoil - maybe even less than that.

If the chokes were rifled, you could play with explosive 'shells' if that's allowed where you play. With those, powder charges are very much reduced to the 2 to 3 dram level, yet the effects on tigers are real history that has been documented - great reading! I did some work with explosive shells (bullets) in a 24 bore, which is too small for real 'work', but that is another story.

This post keeps to the flavour of the title & presents some thoughts that could be explored. I've wanted to find someone who could rifle both chokes or just one choke of a doublegun for me, for some time. What a GREAT gun that would be - kind of like Seyfried's 12 bore H&H Paradox.