Claude-Étienne Minié in the context of "Musket ball"

A musket is a muzzle-loaded long gun that appeared as a smoothbore weapon in the early 16th century, at first as a heavier variant of the arquebus, capable of penetrating plate armour. By the mid-16th century, this type of musket gradually disappeared as the use of heavy armour declined, but musket continued as the generic term for smoothbore long guns until the mid-19th century. In turn, this style of musket was retired in the 19th century when rifled muskets (simply called rifles in modern terminology) using the Minié ball (invented by Claude-Étienne Minié in 1849) became common. The development of breech-loading firearms using self-contained cartridges, introduced by Casimir Lefaucheux in 1835, began to make muskets obsolete. The first reliable repeating rifles, the 1860 Henry rifle and its 1866 descendant the Winchester rifle, superseded muskets entirely. Repeating rifles quickly established themselves as the standard for rifle design, ending the era of the musket.

The Minié ball, or Minie ball, is a type of hollow-based bullet designed by Claude-Étienne Minié for muzzle-loaded, rifled muskets. Invented in 1846 shortly followed by the Minié rifle, the Minié ball came to prominence during the Crimean War and the American Civil War where it was found to inflict significantly more serious wounds than earlier round musket balls. Both the American Springfield Model 1861 and the British Pattern 1853 Enfield rifled muskets, the most common weapons found during the American Civil War, used the Minié ball.

Rifling, the addition of spiral grooves inside a gun barrel, imparts a stabilizing spin to a projectile for better external ballistics, greatly increasing the effective range and accuracy of the gun. Before the introduction of the Minié ball, which themselves needed greasing, balls had to be rammed down the barrel, sometimes with a mallet, because gunpowder residue would foul a rifled bore after a relatively small number of shots, requiring frequent cleaning of the gun. 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 cylindro-conoidal bullet is a type of muzzleloading firearm projectile with a convexly cone-like front end ("nose") and a cylindrical rear body, invented by Captain John Norton of the British 34th Regiment in 1832. It had a cavitied base, so when fired, the thin concavity wall ("skirt") would expand outwards and seal up the bore diameter. The origin of his idea is an interesting one: when in southern British India, he examined the blow pipe darts used by the natives and found that their base was formed of elastic lotus pith, which by its expansion against the inner surface of the blow pipe prevented the leakage of air past it.

In 1836, Mr. W. Greener, a London-based gunsmith, improved on Norton's bullet design by inserting a conoidal wooden plug into its base. Although both inventions were rejected by the British Ordnance Department, the idea was taken up in France, and in 1849 Claude-Étienne Minié adopted Greener's design and produced the "Minié ball".