Before the development of the Minié ball, muzzle-loading rifles were not used in combat situations because of how difficult they were to load. Because the ammunition used had to engage the spiral grooves, or rifling, inside the rifle barrel, it had to be equal in diameter to the barrel, and shooters would have to jam the bullet into the rifle by force. In addition, the rifle tended to become even more difficult to load as gunpowder residue collected inside the barrel.

The French army officer Claude-Etienne Minié was not the first to come up with the design of a bullet that expanded when fired, but he simplified and improved on earlier designs–including those developed by Britain’s Captain John Norton (1818) and William Greener (1836)–to create his namesake bullet in 1849. Cylindrical in shape, with a conical point and a hollow base containing an iron plug, the Minié bullet was smaller than the diameter of a rifle barrel, and could be easily loaded, even when the rifle became dirty.

When a rifle containing a Minié bullet was fired, the bullet was rammed back on the charge, which exploded and sent the bullet hurtling down the barrel. On its way, the iron bullet expanded, gripping the spiral rifling and spinning so tightly along its course that its range and accuracy were greatly increased, with fewer misfires. The effective range of a Minié bullet was from 200 to 250 yards, a huge improvement on earlier ammunition.

The French army never adopted the Minié bullet, but the British did, paying Minié for his patent to use the ammunition in 1851. During the Crimean War of 1853-56, which pitted Britain, France and the Ottoman Empire against Russia, the bullet so improved the effectiveness of infantry troops that 150 soldiers using the minié could equal the firing power of more than 500 with a traditional musket and ammunition.

In the early 1850s, James Burton of the U.S. Armory at Harper’s Ferry, Virginia, improved further on the Minié bullet by eliminating the need for the iron plug and making it easier and cheaper to mass-produce. It was adapted for use by the U.S. military in 1855.

During the Civil War (1861-65), the basic firearm carried by both Union and Confederate troops was the rifle-musket and the Minié ball. The federal armory in Springfield, Massachusetts, produced a particularly effective rifle-musket that had a range of around 250 yards; some 2 million Springfield rifles were produced during the war.

The long-range accuracy of the Minié ball meant that the traditional model of warfare, when infantry and cavalry assaults could be successful, was over. Soldiers armed with a minié-loaded rifle could hide behind trees or blockades and take down approaching forces before they could get close enough to cause any damage. Weapons of an earlier age, such as the bayonet, became almost obsolete in this new kind of warfare, and the role of cavalry and field artillery was greatly reduced. Casualty figures for the American Civil War reached staggering proportions, with more than 200,000 soldiers killed and more than 400,000 wounded. The rifle-musket and the Minié bullet are thought to account for around 90 percent of these casualties.