A repeating firearm carries a supply of ammunition and provides a mechanical means to move the cartridges in and out of a single chamber. The goal is to achieve high firing rates while eliminating user handling of ammunition between shots.
Multi-shot wheel lock pistol
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Multishot wheel lock and flintlock firearms are examples of the earliest designs that called for loading one charge (powder and ball) atop another until several shots occupied the barrel. Multiple ignition devices (locks) lined up or a single moving lock would discharge the loads. The downfall of this system was that the front charge could accidentally ignite one or more of the others.
Later, multibarrel arms offered more shots in rapid succession, but the increased bulk and weight of more than two barrels was unacceptable. Attempts at multiple moving chamber blocks (each separately charged) was a good start but far too complex for the ignition systems and propellants of the time.
The first effective repeaters appeared in the percussion era. Percussion cap ignition reduced the bulk of the firing system, leaving room for a repeating mechanism that could move between a single barrel and the firing mechanism. Some looked like harmonicas, with a rectangular block bearing the chambers moving through a central frame. Each moved in turn behind the barrel for firing.
Others, like the Cochran revolver, had flat cylinders with chambers arranged around the circumference, resulting in a very bulky firearm that was too impractical to carry.