Griffith also suggests that although troops did open fire at 400 yards and more on occasion, the more experienced they became the less likely they were to do this as it wasted ammunition.
Hess is very good and follows on from Griffith and Mark Grimsley’s Surviving Military Revolution: The U.S. Civil War,
Macgregor Knox and Williamson Murray, eds., The Dynamics of Military Revolution, 1300-2050 (Cambridge: Cambridge University Press, 2001)
Hess’ asssessment for the range for fire combat in the ACW is between 96 and 114 yards.
So whatever the theoretical performance of the rifled musket and the expectations of tacticians, the practical range seems to have been around 100 yards.