Minié ball in the context of "Air rifle"

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 The first reliable repeating rifles, the 1860 Henry rifle and its 1866 descendant the Winchester rifle, superseded muskets entirely.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.

An air gun or airgun is a gun that uses compressed air or other pressurized gases to fire projectiles, reminiscent of the principle behind the ancient blowgun. This is in contrast to a firearm, which shoots projectiles using pressure generated via combustion of a chemical propellant, most often black powder in antique firearms and smokeless powder in modern firearms.

Air guns come in both long gun (air rifle) and handgun (air pistol) forms. Both types typically propel metallic projectiles that are either diabolo-shaped pellets or spherical shots called BBs, although in recent years Minié ball-shaped cylindro-conoidal projectiles called slugs are gaining more popularity. Certain types of air guns (usually air rifles) may also launch fin-stabilized projectile such as darts (e.g., tranquilizer guns) or hollow-shaft arrows (so-called "airbows").

Claude-Etienne Minié (13 February 1804 – 14 December 1879) was a French military instructor and inventor famous for solving the problem of designing a reliable muzzle-loading rifle by inventing the Minié ball in 1846, and the Minié rifle in 1849. He succeeded the pioneering work of Henri-Gustave Delvigne and Louis-Étienne de Thouvenin.

Minié served in a number of African campaigns with the Chasseurs, after which he was eventually promoted to captain. In 1846 he designed the Minié ball, a cylindrical bullet with a conical hollow in the base which expanded when fired. This projectile, combined with his rifle, resulted in a major improvement in firearm accuracy.

A shotgun slug is a heavy projectile (a slug) made of lead, copper, or other material and fired from a shotgun. Slugs are designed for hunting large game, and other uses, particularly in areas near human population where their short range and slow speed helps increase safety margin. The first effective modern shotgun slug was introduced by Wilhelm Brenneke in 1898, and his design remains in use today. Most shotgun slugs are designed to be fired through a cylinder bore, improved cylinder choke, rifled choke tubes, or fully rifled bores. Slugs differ from round ball lead projectiles in that they are stabilized in some manner.

In the early development of firearms for the year 1875, smooth-bored barrels were not differentiated to fire either single or multiple projectiles. Single projectiles were used for larger game and warfare, though shot could be loaded as needed for small game, birds, and activities such as trench clearing and hunting. As firearms became specialized and differentiated, shotguns were still able to fire round balls, though rifled muskets were far more accurate and effective. Modern slugs emerged as a way of improving on the accuracy of round balls. Early slugs were heavier in front than in the rear, similar to a Minié ball, to provide aerodynamic stabilization. Rifled barrels, rifled slugs and rifled choke tubes were developed later to provide gyroscopic spin stabilization in place of or in addition to aerodynamic stabilization. Some of these slugs are saboted sub-caliber projectiles, resulting in greatly improved external ballistics performance.

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".