Well, you've got a point. The first mass-produced revolver was the Colt Paterson, produced from 1836 to 1849. Very early on, Samuel Colt did claim to be producing guns with mostly interchangeable parts, using machine tools with jigs, shaped cutters and fixtures. In this he was continuing something known as either Armory Practice or The American System, which would have made it possible for his guns to be made with the economies of scale found in places like the Springfield Armory, enough to equip an army. These guns- which included revolving rifles; shoulder arms- could also have fired faster than the standard issue 1855 or 1861 Springfield muzzle-loading rifles.

And there was a trial. The US Army had recognized quite early on that cavalry had a difficult time with muzzleloading arms. When you are on a horse, it's awkward to load with a ramrod, especially something long. Even the shorter cavalry carbines usually had swivels mounted on them , to be clipped to a shoulder strap so they couldn't be dropped and lost. Pistols had therefore often been used by cavalry. Alternative designs were tried to the standard horse-pistol with shoulder stock. Colt's was among them. When his Model 1855 revolving rifle was tried, it was adopted but didn't work that well. There were two large problems with it.

First, although they were simple compared to a modern Kalashnikov, they were complex compared to a normal musket. Black powder creates a corrosive fouling, which has to be cleaned off thoroughly or the gun will start to rust, and soldiers were accustomed to completely disassembling and re-assembling their guns to do this: soldiers had a great deal of trouble doing this with the Colt.

Second, and most importantly, the Colt was still a muzzle-loader in essence. The cylinder chambers were loaded from the front, with powder and then a bullet. When the gun was fired, sometimes gas from this would leak between the front of the cylinder and the rear of the barrel, get past one of the bullets in the adjoining chambers and set off the charge. This chain fire could damage the gun, damage the soldier, or both, and quickly became greatly feared by the troops. It's possible to avoid this by putting grease ahead of the bullet, to seal it off, but this step was difficult to ask of a man re-loading on horseback in the midst of a battle. So, although almost 5,000 were sold to the Army before the Civil War, during the War cavalry units were more often equipped with carbines by Spencer, Sharps , etc . And eventually, when metallic cartridges became standard, revolvers could be loaded more quickly and safely. And yes, when people today shoot a repro cap-and-ball revolver, they do put grease over the bullets in the cylinder.

Fuller: The Breechloader in the Service