One of the main guns used in The Younger Days is the Spencer Repeating Rifle. It was a revolutionary weapon for the Union Army in the Civil War. One of the most enjoyable and time consuming aspects of research for The Younger Days was on the weapons. Colt pistols, Sharp’s rifles, and even a hand sickle became integral parts of the book.
Here the link to a fine Wikipedia page for background and history of the Spencer Repeating Rifle.
And a recent video of firing and antique Spencer.