Description
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. At the beginning of World War II, over 118,000 M1917 Revolvers were still in U.S. arsenals, and in 1940 these were parkerized, refurbished and issued to U.S. Military Police units, and also to artillerymen and tank crews overseas. They continued being in service in these roles during the Korean War, and during the Vietnam War they were used by support troops and tunnel rats.
The Colt M1917 Revolver was basically a modified Colt New Service (aka Colt M1909), modified to shoot .45 ACP instead of .45 Long Colt. The New Service revolver was in itself based on the Colt Model 1892, which was originally chambered for .38 Long Colt and had been proven inadequate in stopping power during the Philippine-American War (1899-1902).
Source: Wikipedia