When the US was debating getting involved in WWI, S&W realized the military would need more pistols than Colt could supply. The engineers at S&W were tasked with modifying the N frame to handle the 45 ACP cartridge. Chambering and firing a rimless cartridge was not a problem. Getting the fired case out of the cylinder was the issue. S&W came up with two solutions, metal clips that held 3 or 6 cartridges in place and gave the ejector star something to eject. The military opted for the 1/2 moon clip as it was simpler and allowed for more compact storage of loaded ammunition.
The Model 1917 Hand Ejector
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After the war, S&W continued to build the same revolver and it differs from the Military very only by the inclusion of the S&W logo.
A Commercial 1917
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A few of the 1917s were altered to include target sights but there was no real “target model” in 45 ACP until 1950.
Prior to WWII, the Brazilian Government placed an order for the Model 1917 revolver. These were built with the commercial model.
A Brazilian 1917 with the barrel shortened to 4”.
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After WWII ended many gunsmiths offered conversion of the standard S&W “long action” to a shorter trigger pull. It was popular enough that S&W came out with their own version in 1950 and upgraded all of their lines.
Here is a Model 1950 Hand Ejector 45 ACP Army. The differences noticeable are hammer shape, no visible stud under the thumb piece and much better sights. The rear sight is a squared notch and the front sight is 1/8” wide. The front sight on this particular revolver has been modified by a previous owner who used the piece.
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Also in 1950, S&W introduced the first of the Target grade 45 ACP revolvers, the Model 1950. This included the short action, a reinforced ejector lug and target sights.
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In 1955, S&W “improved” the 1950 Target Model with the addition of a heavier barrel.
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In 1957, S&W started using numbers to designate the different models. The 1950 Army became the Model 22, the 1950 Target became the Model 26 and the 1955 Target became the Model 25. The Model 26 was discontinued in 1961. The Model 22 was discontinued in 1966 and the Model 25-2 was discontinued in 1991.
In 2005, S&W introduced the Model 22-4, Thunder Ranch Revolver. This is a 4” version of the 1950 Army Model but added a reinforced ejector lug.
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Two years later, 2007, a standard version was also included in the line up. The only difference was the Thunder Ranch Model used TRR to start the serial number and the standard version did not. The standard version was available blued, nickel plated or with a casehardened frame.
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Also available in 2007 was the “Classic Model of 1917” which in reality was just a reintroduction of the Model 1950 Army. It too could be blued, nickle plated, or case hardened.
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There were also various engineering changes (direction of threads, etc) but I tried to highlight the major differences.
S&W also introduced the 625 series of revolvers in stainless steel but the OP did not ask about those.
Kevin