I have had some friendly discussions as to whether the Model 1909 was actually adopted as the standard service pistol, or only purchased as a stop-gap until an automatic pistol was available.
FWIW, my arguments for adoption are that 1) it was given a model number, 2) holsters and other equipment were made for it, 3) special ammunition was made for it, 4) that no one in 1909 knew when or even if an auto pistol would be adopted, 5) it was used as the standard against which the Colt and Savage auto pistols were tested. On the latter, note that the revolver fired 6000 rounds, shot for shot with the auto pistols; it had two malfunctions, both due to dead primers, and no breakages.
The ammunition was not the .45 Colt (".45 Long Colt") as often written. The issue ammunition was the Revolver Ball Cartridge, Model 1909.
When the Model 1909 was first tested by the Army, they found that the small rim of the .45 Colt (which had been no problem in the rod ejection Model 1873), caused ejection problems in the Model 1909. So the Army made its own cartridges at Frankford, giving them a larger rim. There was no contract production and no cartridges were ever made for the civilian market. But the Army did not issue .45 Colt cartridges or the .45 Army cartridge (the round made for use in either the Model 1873 or the Schofield) with the Model 1909 revolver, only Model 1909 cartridges.
One note of interest is that except for the larger rim, the Model 1909 round is identical to the .45 Colt, but cannot be used in the SAA Colt unless loaded in only every other chamber, making the old "six shooter" into a "three shooter."
Here are some pics. The top is a comparison of the Model 1909 cartridge (R) with the regular .45 Colt (L). The other compares the .45 Colt (R) with the .45 Army Revolver cartridge; this one is Benet primed.
Jim