The adoption of 45acp revolvers and half moon clips didn't have anything to do with speed of reloading. As the US was about to get into WW1 in 1917, they had no where near enough 1911's. Most of the arms manufacturers were busy making guns for other countries who had been fighting since 1914. Rifle production was more of a priority so not a lot of service pistols had been built up to 1917. As the US appraised their manufacturing capacity, they found that there was no way they would be able to tool up to produce the necessary 1911's for their entry into the war. The solution was to look at altering guns that were already in production. Colt had the New Service large frame revolvers and Smith had what would one day become the N frame revolver. It was simple enough to change their existing tooling to cut the proper barrels and chambers. The problem was that the Army was buying 45acp ammo and wanted their handguns chambered to fire it. Although it was simple enough to cut chambers and barrels, ejecting a rimless round from a swing open revolver was problematic. Enter Joseph Wesson, Daniel's son. He came up with and patented the half moon clip. Each clip holds 3 rounds and engages with the extractor star, which allows the rounds to be removed from the chamber using the ejector rod. The concept of the half moon clip, and later the 1/3 moon and full moon clips came about because of extraction, not loading. The Army wanted the gun to be usable without the clips in a emergency. Imagine being in a WW1 trench with a pocket full of loose 45's and no clips. To accommodate that, a shoulder is machined into the chambers so that a round without a clip will headspace high enough to be fired. Colt had a lot of New Service, 45 Colt cylinders on hand so to get a jump on production, they started with those. The early Colt's will not fire an individual 45 because they lack the ledge inside the chambers. Shortly after the war ended, the government declared all of the 1917 revolvers surplus. They were committed to the 1911 and had no interest in revolvers. Hundreds of thousands were sold off to the public. In 1925, the Peter's ammo company came up with the 45 Auto Rim so that the guns would function better without the clips. I do not believe that any company specifically chambered a revolver in 45AR. The full moon clip would come along later and I believe in response to the use of 45ACP revolvers in the action games that started to become popular in the 60's and 70's. So the main purpose of the clip was to provide a way to eject rounds. Although Smith's have the ledge inside the chambers to allow single loading and firing, when you drop in a clip full of ammo the clip is what keeps the base of the round against the recoil shield and sets the head space and the mouth of the case is a couple of thousands off the ridge so it has no role. That is why you can heavily roll crimp 45's that will be used in this manner.