The M1917 Revolvers were six-shot, .45 ACP, large frame revolvers adopted by the United States Military in 1917, to supplement the standard M1911 pistol during World War I. There were two variations of the M1917, one made by Colt and the other by Smith & Wesson. They used moon-clips to hold the cartridges in position, facilitate reloading, and to aid in extraction since revolvers had been designed to eject rimmed cartridges and .45 ACP rounds were rimless for use with the magazine-fed M1911. After World War I, they gained a strong following among civilian shooters. A commercial rimmed cartridge, the .45 Auto Rim, was also developed, so M1917 revolvers could eject cartridge cases without using moon-clips. Background During World War I, many U.S. civilian arms companies including Colt and Remington were producing M1911 pistols under contract for the U.S. Army, but even with the additional production there was a shortage of sidearms to issue. The interim solution was to ask Colt and Smith & Wesson, the two major American producers of revolvers at the time, to adapt their heavy-frame civilian revolvers to the standard .45 ACP pistol cartridge. Both companies' revolvers utilized half-moon clips to extract the rimless .45 ACP cartridges. Daniel B. Wesson's son Joseph Wesson invented and patented the half-moon clip, which was assigned to Smith & Wesson, 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. The Smith & Wesson model The Smith & Wesson Model 1917 is essentially an adaptation of the company's .44 Hand Ejector 2nd Model chambered instead in .45 ACP and employing a shortened cylinder and a lanyard ring on the butt of its frame. The S&W M1917 differs from the Colt M1917 in that the S&W cylinder has a shoulder machined into it to permit rimless .45 ACP cartridges to headspace on the case mouth (as they do in pistols). The S&W M1917 can thus be used without half-moon clips, though empty .45 ACP cases, being rimless, must be poked out manually through the cylinder face as the extractor star cannot engage them. The Colt model Colt had previously produced a version of their .45 Long Colt caliber New Service model, designated the M1909, to replace their .38 Long Colt caliber M1892 revolvers that had demonstrated inadequate stopping power during the Philippine–American War. The Colt M1917