The practice seems to have started early in the Bullseye shooting game.
You would test each chamber individually to find the most accurate one. Sometimes you'll find an old revolver where numbers were stamped. Other times you might just find a center punch mark indicating the most accurate chamber.
For the 50 yd slow fire stage, where you have 10 minutes to shoot 10 shots, there was plenty of time to single load your revolver shot by shot. Later, after pistol matches went from being run by the United States Revolver Association and went over to the NRA, the practice was banned from matches. You had to load and fire 5 shots at a time. That's why the familiar range command is "with five rounds, load".
Anyhow, the practice might well have been the inspiration for the Colt "Camp Perry" model. At first casual glance it looked like a revolver but it was a single shot target pistol built on a revolver frame. Instead of having a cylinder, though, it had a single shot breech that swung out. The barrel was even attached to the breech, eliminating the barrel/cylinder gap and forcing cone, etc.
See attached from Julian Hatcher's "Textbook of Pistols & Revolvers" first printed in 1927.
