The Minié ball, or Minni ball, is a type of muzzle-loading spin-stabilized rifle bullet named after its co-developer, Claude-Étienne Minié, inventor of the Minié rifle. It came to prominence in the Crimean War and American Civil War. The development of the Minié ball was significant because it was the first projectile which was small enough to be easily put down the barrel of a rifled long gun. Rifling – the addition of spiral grooves inside the gun barrel, which imparted a spin to the bullet – greatly increased the range and accuracy of the gun. Prior to the Minié ball, bullets had to be jammed down the rifle barrel, sometimes with a mallet, and after a relatively small number of shots, gunpowder residue built up in the spiral grooves, which then had to be cleaned out. Both the American Springfield and the British Enfield rifles – the most common rifles used during the American Civil War – used the minié ball.
The Minié ball was a conical bullet with three exterior grease-filled grooves and a conical hollow in its base. The bullet was designed by Minié with a small iron plug and a lead skirting. Its intended purpose was to expand under the pressure and obturate the barrel and increase muzzle velocity.
The precursor to the Minié ball was created in 1848 by the French Army captains Montgomery and Henri-Gustave Delvigne. Their design was made to allow rapid muzzle loading of rifles, an innovation that brought about the widespread use of the rifle rather than the smoothbore musket as a mass battlefield weapon. Delvigne had invented a ball that could expand upon ramming to fit the grooves of a rifle in 1826. The design of the ball had been proposed in 1832 as the cylindro-conoidal bullet by Captain John Norton, but had not been adopted.
Captain James H. Burton, who was an armorer at the Harper's Ferry Armory, developed an improvement on Minié's design when he added a deep cavity at the base of the ball, which filled up with gas and expanded the bullet's rim upon firing. The result was not only better range, but also a cheaper bullet, which was used in the Crimean War and then the American Civil War. Burton's version of the ball weighed two ounces.
The bullet could be quickly removed from the paper cartridge with the gunpowder poured down the barrel and the bullet pressed past the muzzle rifling and any detritus from prior shots. It was then rammed down the barrel with the ramrod, which ensured that the charge was packed and the hollow base was filled with powder. When the rifle was fired, the expanding gas pushed forcibly on the base of the bullet, deforming the skirt to engage the rifling. This provided spin for accuracy, a better seal for consistent velocity and longer range, and cleaning of barrel detritus.
Wounds inflicted by the conical Minié ball were different from those caused by the round balls from smoothbore muskets, since the conical ball had a higher muzzle velocity and greater mass, and easily penetrated the human body. Round balls tended to remain lodged in the flesh, and they were often observed to take a winding path through the body. Flexed muscles and tendons, as well as bone, could cause the round ball to deviate from a straight path. The Minié ball tended to cut a straight path and usually went all the way through the injured part; the ball seldom remained lodged in the body. If a Minié ball struck a bone, it usually caused the bone to shatter. The damage to bones and resulting compound fractures were usually severe enough to necessitate amputation. The entire point of the minie ball was to damage the bones, and have them do the damage themselves. A hit on a major blood vessel could also have serious consequences.
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