Minié ball

[3] The development of the Minié ball was significant because it was the first projectile type that could be made with a loose enough fit to easily slide down the barrel of a rifled long gun, yet maintain good accuracy during firing due to obturation by expansion of the bullet's base when fired.

The Minié ball is a cylindro-conoidal bullet with grease-filled cannelures on its exterior and a cone-shaped hollow in its base.

[citation needed] A precursor to the Minié ball was created in the 1830s by French Army captains Montgomery and Henri-Gustave Delvigne.

[citation needed] Captain James H. Burton, an armorer at the Harpers Ferry Armory, developed a major improvement on Minié's design when he added a deep conical cavity at the base of the ball,[clarification needed] which more efficiently filled up with gas and expanded the bullet's skirt upon firing.

[2]: 314–315 The Minié ball could be quickly removed from the paper cartridge, with the gunpowder poured down the barrel and the unexpanded bullet pushed down after it passed the muzzle rifling and any carbon build up from prior shots.

[2]: 314–315 One of the more infamous documented cases involving Minié ball injuries concerned a Confederate soldier wounded during Jubal Early's raid on Washington, D.C. on July 12, 1864.

The soldier, a private in the 53rd North Carolina Infantry, was hit in the side of the head by a .58 caliber Minié ball, which shattered his skull and lodged in the right hemisphere of the brain.