Air gun

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").

The first air guns were developed as early as the 16th century, and have since been used in hunting, shooting sport and even in warfare. There are three different power sources for modern air guns, depending on the design: spring-piston, pneumatic or bottled compressed gas (most commonly carbon dioxide and recently nitrogen).

Air guns represent the oldest pneumatic technology. The oldest existing mechanical air gun dates back to about 1580, and is currently kept in the Livrustkammaren Museum in Stockholm. This is approximately what most historians recognize as the beginning of the modern air gun.

Throughout 17th to 19th century, air guns in .30 to .51 calibers were used to hunt big game, deer and wild boar. These air rifles were charged using a pump to fill an air reservoir and produced velocities from 650 to 1,000 ft/s (200 to 300 m/s). They were also used in warfare, the most recognized example being the Girandoni air rifle, a repeating rifle used by Austria in the 1788 war against Turkey.

At that time, they had compelling advantages over the primitive firearms of the day. For example, air guns could be discharged in wet weather and rain (unlike both matchlock and flintlock muskets), and discharged much faster than muzzle-loading guns. Moreover, they were quieter than a firearm of a similar caliber and produced no muzzle flash or smoke cloud when fired. Thus, they did not give away the shooter's position or obscure the shooter's view, unlike the black powder muskets of the 18th and 19th centuries.

In the hands of skilled soldiers, they gave the military a distinct advantage. France, Austria and other nations had special sniper detachments using air rifles, mostly Jäger (infantry). The Austrian 1779 model was named Windbüchse (literally "wind rifle" in German). The gun was developed in 1768 or 1769 by the Tyrolean Ladins watchmaker, mechanic and gunsmith Bartholomäus Girardoni (1744–1799) and is sometimes referred to as the Girandoni air rifle or Girardoni air gun in literature (the name is also spelled "Girandony", "Giradoni" or "Girardoni".). Adopted by the Austrian leadership in 1779, the Windbüchse was about 4 ft (1.2 m) long and weighed 10 pounds (4.5 kg), about the same size and mass as a conventional musket. The air reservoir was a removable, club-shaped, butt. The Windbüchse carried twenty-two .51 caliber (13 mm) lead balls in a tubular magazine. A skilled shooter could fire off one magazine in about thirty seconds. A shot from this air gun could penetrate a one-inch-thick (2.5 cm) wooden board at a hundred paces, an effect roughly equal to that of a modern 9×19mm or .45 ACP caliber pistol.

Circa 1820, the Japanese inventor Kunitomo Ikkansai developed various manufacturing methods for guns, and also created an air gun based on the study of Western knowledge ("rangaku") acquired from the Dutch in Dejima.