Staff Writer (Updated: 5/5/2016):
The United States Army commissioned both Colt and Smith & Wesson to produce a revolver under the official "M1917" ("Model 1917") designation. The weapon would be a no-frills firearm chambered for the .45 ACP cartridge - the same cartridge as featured in the Colt M1911 - and be based on existing frames for expediency. Patriotic fervor aside, both concerns realized the war was a lucrative money-making venture and moved to produce guns to whatever military requirement. The two endeavors eventually produced slight variations in the M1917 revolver line as a whole - the Colt Model 1917 being based on the company's existing .45 caliber New Service Model with Smith & Wesson electing to use their "SW Second Model .44 Hand Ejector" for the Model 1917 requirement - a gun already in "hybrid" production in a .455 Webley form for the British military.
Overall design of the Smith & Wesson Model 1917 was conventional and followed the original .44 design closely (save for the required .45 ACP chambering). The firearm was developed with a solid frame - a bridge over the rotating cylinder - to provide a more robust body. The frame was of solid metal with the barrel naturally seated at the front of the rotating cylinder and an ejector rod fitted underneath. The ammunition cylinder was fluted and held six .45 cartridges that were inserted from the rear. The exposed hammer spur was easily visible from the rear of the frame and the pistol grip padded with smooth wood for some limited comfort. The curved trigger assembly sat within an oblong ring under the cylinder.
Due to the rimless .45 cartridge requirement, the Model 1917 was loaded through three-round "moon clips", a cartridge insertion method patented by Smith & Wesson. In this way, the weapon could be quickly reloaded as three cartridges were inserted at a time. The clip method also allowed the ejector rod to be operated in the normal fashion, the clip essentially acting as the cartridge's "rim" and holding it in place ahead of the firing pin. This aided in the extraction of the spent shell casings and sped up the reloading process as all six chambers could now be refilled at speed. Only a formal U.S. Army request allowed Colt to make use of this same moon clip feature. The cylinder of the SW Model 1917 was also shortened because of the rimless cartridge being used.
SW Model 1917 revolvers were put into play immediately during World War 1. It served as the sidearm of officers, infantryman and support personnel on multiple fronts of the conflict. The revolver proved a solid, durable and reliable system even in the harshest of conditions and gave a good account of itself in combat. The Smith & Wesson Model 1917 series - like the Colt Model 1917 - survived the war and saw use in the conflicts to follow, a testament to its strong design and engineering. After World War 1, Smith & Wesson continued to offer their Model 1917 to police and civilian markets sensing recent war-time performance as a tremendous selling point for the product. In 1920, a rimmed .45 cartridge - the ".45 Auto Rim" - was introduced by the Peters Cartridge Company which allowed moon clips to be disused. Smith & Wesson also manufactured all-new cylinders to handle the standard .45 ACP cartridge of the M1911 and offered these to M1917 owners.
As was the case with many successful World War 1-era firearms, the Smith & Wesson M1917 revolver line continued in service into World War 2 (1939-1945) alongside the competing Colt Model 1917 revolvers and the Colt M1911 semi-automatic pistols where it continued to provide good service. In the pre-war years, the Brazilian government placed an order for 25,000 SW M1917s and designated them as the "M1937" with slight alterations to suite Brazilian military requirements. M1917s then soldiered on in one form or another throughout the Korean War and into the Vietnam War to which the type gradually decreased in their available numbers, making them something of collector's items today. M1917s served in an official capacity until 1954 though private forms endured much longer.
In all, Smith & Wesson produced 153,000 M1917 revolvers to Colt's 150,000 M1917s.