When accuracy is lacking, volume of fire makes up for inaccuracy. Example: machine guns. Furthermore, not being forced to stand straight up, or at best kneeling, in order to reload means troops do not have to be standing or kneeling, and exposed, to fire.I'm sorry aggie, but this sounds like it contradicts what you've said elsewhere. If training marksmanship wasn't high on anyone's list of priorities, then what difference does it make if they had repeaters?
Also, which battles were these that you speak of where repeaters won the day?
Battles where faster firing weapons were decisive, I'll just describe Gettysburg, as its the most fitting. Buford's cavalry division, armed with Sharps, Burnside, Merrill, Ballard, and Maynard breech loading rifles, were able to dismount, fight from cover, and delivery exceptional firepower to the point they repelled numerous concerted attacks by an entire corps.
The Henry Repeating Rifle: The Weapon of Choice! Usage of the Henry Repeating Rifle In the Civil War 1861-1865
Too Little Too Late? The Introduction of the Spencer Rifle
The biggest limitation to mass issue of repeated rifles during the Civil War, at least to the North, was institutional malaise, legitimate logistical problems regarding ammunition consumption, and production problems. However, they were exponentially more effective than a muzzle loading percussion cap rifle, all other things being equal (though they never are).