By the 1850s, every serious military power had largely replaced its standard small arm with some form of muzzle loading rifle. These rifles were collectively called the Minie rifles, after the name of the round they fired (the Minie ball).

But thats problematic, not every weapon was always immediately adopted by every unit, even if the standard weapon was a rifle. For example, [The Irish Brigade](http://en.wikipedia.org/wiki/Irish_Brigade_(\U.S.)#American_Civil_War) during the American Civil War was issued muskets, because the commander wished to use buck-and-shot (a musket ball and several BBs, the standard combat loadout for a musket). He felt that the Buck-and-shot produced more damage up close, and the short range of the smooth bore encouraged aggressive tactics. I have even read (though I cannot currently find) articles which talked about Asian rebels who were still using smooth bore muskets against government forces. All that goes to show that, despite their obsolescence, those weapons are still in use today.