A favorite EDC gun from back in the days of the Old West was a modified Colt Navy or Army, for an ace up the sleeve when needed.
Cap and Ball, a Hungarian YouTube gun channel specializing in black powder smoke poles, tests just such a conversion for accuracy. The test subject is a .36-caliber Uberti 1861 Colt Navy repro that has been given a barrel reduction to just two-inches with an added brass front sight. Of course, with the loading lever cut away, loading the cylinder requires the use of a wooden block and plastic hammer, but hey.
As for the accuracy of the belly gun, watch the video.