Frank Forester wrote in The Complete Manual for Young Sportsmen, published in 1868 that...
"If the change render it more difficult to shoot well, it is a retrograde step, not an improvement. For example, the percussion system is now, in spite of all old-fashioned prejudice and opposition, an admitted improvement on the old flint-and-steel system; and one, not the least, of its advantages is, that it has so much simplified the art of shooting flying, that there are now ten good shots, where there was one, forty years ago.
Consequently, the person who had learned with much toil and labor to shoot excellently with the old flint lock, took up the new percussion piece, and found himself at once, with no farther trouble, twice as good a shot as he was before. It was to him as if his old gun had suddenly doubled its celerity and accuracy of aim. It is certain that no good shot, with flint and steel, ever found himself a bad one with percussion, even on the first trial. Equally certain it is, that, take twenty crack shots with the percussion, and give them the best and most perfectly finished Joe Manton flint-and-steel lock, and the first week they will not kill three fair shots out of ten; in any given time, not one will shoot as well as he did with his copper caps, and probably one half of them will never become respectable shots at all."
Having finished a Kibler Fowler in 16ga, and having shot nothing but percussion to this point, I missed 6 clays in a row. Switching to patterning paper and paying attention to each pull, I finally see what Mr. Forester meant. The timing delay and movement of that lock is akin to having someone bump the stock every shot. At 15 yards for a cylinder bore the patterns were even but high, then low, then right, then left. Putting 2 clays on log pile took 3 shots to break them.
I have a new found respect for those of you who can wing shoot with a flintlock. I have much to learn.