Just saw this Cap'n. Posted my Hollyweird in the wrong place! Another honorable mention in the modern western saga... a "B" rated western called " Good for Nuthin". The main character has a libido problem, but is a total badass despite! The reality is, its a mid 1870's era film and the main character wears an 1851 Navy on the strong side and a '75 Remmie on the left! Even shows him reloading the Navy after a shootout. May be a Hollyweird amalgamation, but for mid 1870's they may have got it right for a change! Use your tried and true Navy of which powder,caps, and ball are plentiful at the time, and use your cartridge revolver as your back up seeing how you may or may not find any ammo for it!
Actually reloading spent cartridge ammo wasn't too complicated back in the day. If you shot a cap and ball revolver, you had almost everything you needed to reload cartridges. A "tong tool" (and primers of course) is about all that was needed to go along with everything else to make reloading cartridges around the campfire not too darn difficult.
I'm surprised that western movies haven't included a bit about "in the field" reloading. Lead sheet was used to make containers for many things carried on a journey, which was then saved and melted down as needed. Black powder velocities needed nothing other than pure lead in bullets, but I'm sure some tin was added on occasion.
The Indians got quite inventive doing this, even modifying spent cartridges into pin fire. A spent brass cartridge was like gold to them.
I'll have to watch that movie for sure. I would imagine his choice was based on what gun he was most comfortable with. He could probably hit better with the '51, but when he had a cap jam his back up didn't have that issue.