David Dardick patented a rather interesting firearm back in the 1950's that combined the principles of a magazine pistol and a revolver, using an open chamber cylinder for which the top of the chamber to be fired was the lower part of the revolver top strap. The cartridges were rounded triangular in cross section, and referred to as "trounds." The venture failed because the pistol was unreliable and looked like a mutant soldering gun. Always a bad notion to neglect aesthetics, at least of some sort, in firearms design. Strictly speaking, not a bad idea, though, and I wonder what what could be done reliability-wise with modern CNC machinery. Also, what pressures could be achieved in the open chamber system with the polymer composites and carbon-fiber materials available now.
You hardly ever see a Dardick pistol, and even the ammunition is uncommon as all get out. I found this box and grabbed it just for the curio aspect.
Attachment 199675Attachment 199677