Using a older style pistol was not all that uncommon in the old west. A gun was very expensive, especially the new fangled cartridge revolvers, not to mention the cartridges themselves. Any mining town would have had large stores of black powder and from what I've heard, even the local druggists carried percussion caps. The process of resize, remove and install a primer in a cartridge was well out of the means of most people.
I do know that when they finally got permission to dig out the ground where the original Spangenberg Gun Shop in Tombstone was at before the fire of March 1882, they found all kinds of revolvers....but the most common by a long way was the 58 Remmie. From that I'd say that there was a place for percussion revolvers well into the 1880's....and probably longer. Look how many originals are still popping up today. A pistol was a major investment and if it went bang....it most likely got used.