The Story of the .45 ACP revolver.
During WW I, the British purchasing Commission approached Smith & Wesson with the porposition of producing Webley revolvers under license for the British Army. Smith & Wesson argued that tooling up would be too expensive and take too long. Instead, the offered to produce their New Century revolver chambered for .455 Eley. They made up a trial gun, and submitted it to the British. The British had two complaints: Eliminate the third lock at the yoke as being too expensive and unnecessary. And eliminate the under lug shrouding the ejector rod, as they feared this might get fouled with mud and not be able to close the cylinder. These changes were made and several thousand were sold to the British.
With America's entry into the war, there was a shortage of M1911 pistols. Smith & Wesson proposed to make the British revolver except chambered for the .45 ACP round. These Smiths had the shoulder in the cylinder and could fire the ACP cartridge, but the half moon clips were nedded for extraction. These became the S&W M1917 revolvers. Colt also produced thei New Service in the same chambering, but the earliest Colts required clips for firing, as they were bored straight through.
Both Colt and S&W produced these as commercial models after the War. Smith & Wesson continued a similar model known as the Army model with fixed sights, and the Target model with adjustable sights.
The Target model was updated in 1950 as the Model 1950 Target Model, while the M1917 became the Model 1950 Army Model. A further modification in the target model became the Model 1955 Target, all these aimed at NRA and USRA bullseye target matches.
With the acceptance of auto loaders in target shooting, revolver use has waned.