The American Civil War, like other wars both before and after, was responsible for a leap in technology regarding advances in weapons and military tactics in the space of a few years.
In the first years of the war, the generals used the same battlefield tactics as was used in the Revolutionary and Napoleonic Wars, when the smoothbore musket was the only weapon available. Fired at 100 yards, these muskets didn't inflict much damage on troops.
Early Civil War troops were massed together in a frontal attack just as in earlier times. The old smoothbore musket still in use necessitated such tactics. Unfortunately, as the war progressed, so did the deadliness of weapons. The . . . "Civil War musket was rifled . . . It completely changed the conditions under which soldiers fought." http://www.civilwarhome.com/civilwarweapons.htm
Troops in a Napoleonic style charge could now be killed at a distance of half a mile. The new technology made the military formations of the past out of date and greatly increased casualties. But it took Civil War generals a long time to change
tactics to match the advanced weaponry of the times.
Small arms carried by soldiers included muskets, rifles, carbines (short barrel rifles), and handguns, that included pistols and revolvers. The principal small arms of both sides were the .58 caliber Springfield musket and .69 caliber Harpers Ferry Rifle. They were muzzle loading arms that fired the minie ball.
Revolvers were used by both sides. The most common were the 1860 Colt Revolver and 1851 Navy. "The Remington New Model and the Starr Army Percussion revolvers were also purchased in large numbers by both sides." http://www.civilwarhome.com/civilwarweapons.htm
The development of the rifle bullet known as the minie ball revolutionized warfare. It caused high numbers of deaths making the American Civil War one of the bloodiest wars.
"In 1848 . . . French Army Captain Claude F. Minie created a smaller, hollow-based bullet that could far more quickly and easily be rammed into the bore, expanding when the weapon was fired to catch in the rifling and be shot spinning out of the barrel. That spin made the minie ball . . ." http://www.civilwarhome.com/civilwarweapons.htm
Artillery also went through a technological transformation, beginning in 1861 with pre-Mexican War smoothbores not much different than those used in the American Revolution and ending in 1865 with the Gatling Gun, a precurser to the modern machine gun. http://www.civilwarhome.com/artillery.htm
These weapons forever changed the tactics of Civil War armies, ending with trench warfare around Petersburg, Virginia in 1864-65. This also led to the foxholes of the early twentieth century wars.
The technology of the 19th century was fast moving, leading to many inventions we use today. And the American Civil War changed the weaponry and battle tactics for all future wars.