except military rifles weren't expected to be reloaded and fired as fast nor as frequently as a musket, i.e. they weren't used for volley fire.
Don't bet anything you do not desire to lose on that.
Volly Fire was still common during the Civil War.
An un-rifled musket was rare.
My guess is over 99% of the long arms issued on both sides were rifled muskets.
We were discussing military rifles such as the HF 1803, the 1807 Contract Rifle, the 1814 Contract Rifle, and the 1817 Contract Rifle, not the rifled musket. The military rifles I was referring to were shot with a patched round ball (the patch could be fabric or paper) and had smaller windage than the military musket. Therefore, it was slower to reload than the musket and more difficult to reload once fouling began to build up.
The rifled musket and its Minie ball is another animal altogether. The Minie ball is smaller than the bore of the rifled musket, and is therefore, easier to load. It does not require any patching material as the hollow base and skirt is designed to expand and fill the rifling in the bore. It could be loaded as fast as a smoothbore musket. And yes, it was still used in volley fire during the Civil War.
The Minie ball and rifled musket had devastating effects during the Civil War and changed battlefield tactics and the nature of warfare. After the Civil War, armies no longer lined up in long lines facing each other and fired volleys as they had for the previous couple hundred years.
Another impact of the rifled musket, along with the cap and ball pistol, was the change in terminology in regards to the size of the bullet and bore. In the day, guns that shot patched round balls were referred to by the size of the ball they shot. The term used was "balls to the pound", meaning the size of ball was determined by how many it took to weigh a pound. The bore ID of the gun was larger to allow for patching material and the buildup of fouling. The difference between the bore ID and ball OD was called windage. The windage in military muskets was usually on the order of .04" to .06" as compared to the windage in civilian rifles of .01" to .02".
Cap-and-ball pistols and the rifled musket with its Minie ball did not use a patch and there was no windage. With their development, the use of the term "caliber" became the norm, and it referred to the ID of the bore rather than the size of the ball or bullet. This convention was solidified with the development of cartridge arms.