I spoke to Paul Roberts many years ago about my Rigby Ball & Shot gun as it was an enigma how it functioned. With no "rifling" but with rifle sights up to 100yards I was puzzled to see even a roundball was to be accurate at that range. I too have fired H&H factory paradox ammo in my gun with no useful result. I also tried a slight larger ball(conical) but with no use. Paul Roberts was very frank in the conversation: "Most of the systems didn´t work". With the exception of H&H paradox system(Fosbery patent) not many gunmakers made many of these systems. Rigby made 24 and that says everything as I see it!. Not very succesful. In my almost 400 book library about hunting in India and Africa these ball guns saw most use in India. Hard roundballs backed with 5dram black was a usefull charge against elephant at `junglerange`. Here they might served the purpose. I presume my Rigby was meant for this. I don´t know how the riflingprofile look in the Colindian Ball & Shot gun. The best way the visulize this is to knock a cylindical bullet up-the-barrel and observe the airgaps. My Rigby has 3 indentments all the way out and sqeezing down to .735" at the muzzle from .743" at the chamber end. Hope this helps a little.