I’ll see your 14-shot Glock and raise you an 1859 Walch 12-shot percussion revolver

“The Walch Navy 12 Shot Revolver Of 1859 is quite a strange cap and ball revolver. It has six cylinder chambers, two hammers, two triggers and fires twelve shots.

“How is that even possible? Well, each cylinder chamber is loaded with two loads. Yes, that is a ball and powder over another ball and powder. The ignition system is farther forward in the chamber for shot number one so that fires first. After that, the second charge is ready to shoot.

“This really rare cap and ball revolver had limited success and was quite a worry if the back charge fired before the front one did.”

http://www.wideopenspaces.com/take-a-look-at-the-rare-walch-navy-12-shot-revolver-of-1859/