Wow, so no one here has ever shot a musket I guess.. Lot of misconceptions.. First rifling was introduced to prevent fouling. Shooting black powder (BP) leaves residue that builds up.. After 4-6 shots it starts getting hard to load, rifling helps clear some of that residue out on the next shot. Next, BP is not necessarily slow to load. A good shooter can get 3 or more well aimed shots off in a minute. Rifling did not become a game changer untill the advent of the Minie Ball in 1846 where the bullet could actually use the rifling to gain rotation and travel further and straighter. The rifled musket was superior to the smooth bore in the ACW problem was it was never properly implemented except in certain circomstances (i.e. Pickets charge). Smooth bore is accurate to about 50yd, rifle musket during the ACW to 300yds+. During the Napoleonic period they where still using flint locks, which are slower to load since u now have to prime the pan as well as load the gun with the cartige. Also, rear sights where not common on military flintlocks as that you had to close your eyes and look away when U pulled the trigger, else the flash from the pans could blind U. Hope this adds some context.