As the French did not use rifled weapons, I feel that accounts of their skirmishers `killing men at long distances` may be taken with several grains of salt.
There are a lot of such accounts. A friend of mine who uses period weapons was firing a French smoothbore fusil and at 80 yards could only put 4 out of 10 shots into a three by four target. Then he thought of wrapping the ball with the cartrige paper before setting it in. [Yes, I know that most ammo had the ball wrapped with the powder] He made sure the ball stayed wrapped. When he did this, he was able to put the ball in the target 7 out of 10 times at 150 yards. I would imagine that the Napoleonic soldiers knew of this procedure too.