The Great War was an interesting mixture of the old and the new, and it was the proving ground for new small arms such as the automatic pistol, but because so many men were being put into the field so rapidly, lots older military firearms were dragged out of storage in arsenals, and many civilian guns were being enlisted for the duration. A good case in point is the Colt Model 1917 New Service revolver.
The standard issue pistol for U.S. forces was the M1911 Colt automatic, but there were not enough of them, so Colt and Smith & Wesson were contracted to manufacture additional arms.
Smith & Wesson devised a method to allow that company's Second Model Hand Ejector and Colt's New Service revolvers to handle the rimless .45 ACP cartridge used in the 199 Government Model auto through the use of half-moon clips.
Colt's New Service revolver proved to be a particularly apt choice for this. The large-frame six-shooter was the company's most robust double-action design to date. Initially offered in 1898, the New Service featured a swing-out cylinder that was opened by means of a catch on the left side of the frame that was pulled to the rear to unlock it. The revolver, chambered in .45 Long Colt, saw U.S. military service as early as 1909 during the Philippine Campaign.
To turn the basic New Service into a Model 1917, the rubber grips were replaced with wood, a lanyard ring was added and the cylinder was modified to handle the half-moon clips.
The initial 50,000 1917s were made with straight chambers, but later guns had stepped chambers, so that in a pinch .45s could be loaded without their clips. In that instance, cases would have to be poked out one at a time with a stick or rod.
By the end of the war, more than 150,000 Model 1917 New Services had been manufactured. Eventually they were removed from service and put into storage, but with the start of the Second World War they were again issued to U.S. forces; the Army and Marines used them in both Europe and the Pacific.