Automatic revolver

An automatic revolver (more correctly, a semi-automatic revolver) is a revolver that uses the energy of firing for cocking the hammer and revolving the cylinder, rather than using manual operations to perform these actions. Examples of genuine semi-automatic revolvers are rare, and the term is more often applied to break-open revolvers with automatic systems for ejecting spent casings on opening.

Description
A standard revolver is a manually operated weapon, using the action of cocking the hammer to advance the cylinder in a single-action, or the action of pulling the trigger to advance the cylinder and cock the hammer in a double action. The idea behind an automatic revolver is to automate both actions, removing the need to manually cock the hammer between shots while retaining the lighter trigger pull of the single-action.

This is accomplished by use of a reciprocating slide on the upper part of the frame, the motion of which is used to rotate the cylinder and cock the hammer in much the same way as is used in the majority of semi-automatic pistol designs.

Examples

 * The Webley-Fosbery Automatic Revolver was the first commercial example, introduced in 1901. It was recoil-operated, and the cylinder and barrel recoiled backwards to cock the hammer and revolve the cylinder. It was distinctive in that cam grooves were milled on the outside of the cylinder to provide a means of advancing to the next chamber—half a turn as the cylinder moved back, and half a turn as it moved forward. .38 caliber versions held 8 shots, .455 caliber versions 6. Around 4,750 were made in total.
 * The Union Automatic Revolver of French origin. An unpopular and unsuccessful weapon, with only around 65 examples made.
 * The Zulaica Automatic Revolver M. Zulaica y Cia., Eibar, Spain. began manufacturing 'Velo-Dog' type pocket revolvers in the early 1900s. In 1905, Zulaica patented an unusual .22LR automatic revolver design, but few were ever manufactured and even fewer have survived. Zulaica started manufacturing 'Eibar' type automatic pistols under French army contracts in 1915 and 1916, and continued to market them commercially up to the 1920s.
 * In 1997, the Mateba company developed a type of recoil-operated automatic revolver, the Mateba Unica auto-revolver, which uses recoil energy to auto-rotate a revolver cylinder holding 6 or 7 cartridges, depending on the model. The company has made several versions of its "autorevolver", including longer barreled and even rifle-like variations, usually chambered for .357 Magnum ammunition, but also available in larger calibers like .44 Magnum and .454 Casull.