The Remington is unique in that when you lower the loading lever, you can just pull the pin out and drop out the cylinder, quick and effective. Colt's required knocking out a pin and removing the barrel. Before the Smith and Wesson patent on metalic cartridge revolvers ran out in 1873, there were lots of cartridge converted Remingtons and Colts. They remained popular for quite a while after the '73 Colt came out because they worked and new 1873 Colts were quite expensive. Eastwoods gun, of course, was a cartridge conversion and he, of course, was firing hollywood blanks.
You can buy cartridge conversion cylinders for BP revolvers, Midway sells 'em. They run around $220, so I won't be buying four or five anytime soon. A Remmie with a couple of BP cylinders would be kinda cool to own, I reckon. Not sure why, but I think it'd be cool. I guess you could use it at a cowboy shoot or something, would strike up a few conversations.
Also, I have read that cavalry soldiers in the civil war would ride into combat with multiple loaded cylinders and Remington '58s. That was the definition of fire power back in those days. I think I'd rather have four or five walkers strapped to the horse, too. Actually, I would NOT have wanted to be anywhere near a civil war battlefield, chicken I guess.