Moon clips

A moon clip is a ring-shaped or star-shaped piece of metal designed to hold multiple cartridges together as a unit, for simultaneous insertion and extraction from a revolver cylinder. Moonclips may either hold an entire cylinder's worth of cartridges together (full moon clip), half a cylinder (half-moon clip), or just two neighboring cartridges. The two-cartridge moon clips can be used for those revolvers that have an odd number of loading chambers such as five or seven and also for those revolvers that allow a shooter to mix both rimless and rimmed types of cartridges in one loading of the same cylinder (e.g., 2 adjacent rounds of .45 ACP, 2 rounds of .45 Colt, and 2 rounds of .410 in a single six-chamber S&W Governor cylinder).

Moon clips can be used either to chamber rimless cartridges in a double-action revolver (which would normally require rimmed cartridges), or to chamber multiple rimmed cartridges simultaneously. Moon clips are generally made from spring grade steel, although plastic versions have also been produced. Unlike a speedloader, a moon clip remains in place during firing, and after firing, is used to extract the empty cartridge cases.

The modern moon clip was devised shortly before World War I (circa 1908). The device then became widespread during the war, when the relatively new M1911 semi-automatic pistol could not be manufactured fast enough for the war effort. The U.S. War Department asked Smith & Wesson and Colt to devise ways to use the M1911's .45 ACP rimless cartridge in their revolvers. The result was the M1917 revolver, employing moon clips to chamber the military-issue .45 ACP ammunition. Smith & Wesson invented and patented the half-moon clip, but at the request of the Army allowed Colt to also use the design free of charge in their own version of the M1917 revolver.

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