This would also explain the comments about recent misfires, not so common with cartridges, but very common in black powder. It may explain how the gun was still loaded after a previous shooting session with live rounds, as unloading is not as easy, or obvious, as removing a cartridge.
During that period of the Old West there was a rapid development in firearm technology and brass self-contained cartridges were just coming out. Modern firearms could be a little hard-to-obtain out there so it was common for a smith to modify a Civil War Cap & Ball pistol to one that used the newer technology.
Think of Clint Eastwood’s revolvers in “The Outlaw Josey Wales”. That was a converted Cap & Ball piece, but considering he was a Confederate soldier on the run immediately after the cessation of hostilities the weapon probably wouldn’t have been converted. Yet I don’t recall Clint ever shown reloading in that movie. Maybe he had a “Dirty Harry” speed-loader cobbled together considering the volume of lead he was putting out?