Actually, the 69th New York is one of the few Federal Units I know some details on, as they got the closest to the sunken road during the Battle of Fredericksburg and they were up against a Confederate Irish Brigade (Cobb's).
http://historyarch.com/2017/12/12/an-american-tragedy-at-fredericksburg-clash-of-the-irish-brigades/
The Federal Irish Brigade was formed VERY early in the War when the North just did not yet have enough "New model" M1861 Rifle Muskets made to issue to the huge numbers of soldiers who needed arms. So like many, if not most "Non Regular U.S. Regiments" in the early War period, they got issued what was available and that usually was a M1840 Percussion Smoothbore at best to at worst, some hastily purchased out of date and often worn European percussion converted smoothbore muskets.
In the Pre War years and after the M1855 Rifle Musket was delivered to REGULAR U.S. Infantry units, they began the first real marksmanship training and actually used their Rifled Muskets as far as 700 yards in combat. This was "in the west" where they often used what was later called "Skirmisher Tactics," so there wasn't the blinding clouds of black powder smoke from huge formations, that didn't allow them to shoot much beyond 100 yards - as was often the norm in the UnCivil War. The thing people don't think about though,
is these were already well trained and disciplined Soldiers who were then given additional marksmanship training to properly use the much longer range Rifle Muskets and the Tactics that made them effective. They weren't starting as raw recruits who often didn't know their left foot from their right and a huge amount of available time was eaten up just in basic training of the early War Volunteers.
In the kind of combat in the East where large formations of soldiers were the norm, a single volley would often cloud the Unit firing to the point they could not see the enemy at all and for a time till the smoke dissipated. Add to the fact the same thing was happening with the "other side's" forces, once they fired, they were also sheathed in smoke clouds. A couple more quick volleys from each side and neither side could see individual targets to aim at. So even though the Rifled Muskets of the day could be used at much longer distances than 100 yards, the Black Powder used by both sides caused much of the combat to be 100 yards or less. At that distance, Buck and Ball from Smoothbores was very effective indeed.
Gus