Main Question or Discussion Point
Wikipedia's article on rifles in the American Civil War mentions this:
Is it true that smoothbore guns have a flatter trajectory than rifles? Can someone explain the physics of why that would happen?In Gettysburg, the Last Invasion, (Guelzo, Allen C. (2013). Gettysburg: The Last Invasion. Knopf. p. 656. ISBN 978-0-307-59408-2.) Guelzo also points out the technical difficulty of aiming a rifled musket. While rifling improved overall accuracy of muskets, the rifling also formed a trajectory that caused the bullet to quickly "drop" from where it was aimed (in contrast to the flat trajectory of smoothbore muskets). Thus to hit a target at distances beyond 40–50 yards, the rifleman would require knowledge of trajectory and distance, aiming the rifle at a precise angle above the target. In actual battlefield situations, such precise aiming was virtually impossible. Under the stress of battle, virtually every infantryman asked about aiming on the battlefield replied that in practice, the best one could do was "simply raise his rifle to the horizontal, and fire without aiming." (Guelzo p. 62).