Some sportsmen found large smoothbore ball guns worked fine at the ver short ranges that they hunted dangerous game, as ball stripped over the rifling at that time with the massive powder charges used. Forsythe to correct that, developed his style of rifling which was wide grooves, ver narrow lands and ver slow twist, say 1 in 110inches, just enough to stabiliize a ball over longer distances. Some of us here have rifles with such rifling and have found them to shoot well.
I suspect the paradox gun was a breech loading development. In the good old days I am sure hunters may have loaded their muzzle loading ball guns with both shot in one barrel and ball in the other, especially when hunting large moggys.