I think so too.
This video shows that the rifled musket is absolutely capable of consistently hitting a target at 300 yards when the trajectory of the bullet is considered. (
https://www.youtube.com/watch?v=DPN9N-58RIo&t=3s) The same author previously mentioned (Hess) states that MG Cheatham "recalled that on the battlefield of Franklin, where the Army of Tennessee attacked across a broad, open area, bodies of his men lay as far away from the Federals as 400 yards, but the great majority of dead and wounded lay within 50 yards of the defenders." This is from his book "Civil War Infantry Tactics: Training, Combat, and Small Arms-Unit Effectiveness" which I highly recommend for those interested in just how thousands of men got maneuvered around on a battlefield in both theory and practice.
The reason given for not using the weapon much at long range comes down to lack of training in both armies. It seems to me that military authorities just assumed that if the rifle 'could' hit targets at long range, it 'would' hit targets at long range.