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 and handgun 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 may also launch fin-stabilized projectile such as darts or hollow-shaft arrows.
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.
History
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. 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, 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. The Austrian 1779 model was named Windbüchse. The gun was developed in 1768 or 1769 by the Tyrolean Ladins watchmaker, mechanic and gunsmith Bartholomäus Girardoni and is sometimes referred to as the Girandoni air rifle or Girardoni air gun in literature. Adopted by the Austrian leadership in 1779, the Windbüchse was about long and weighed, 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 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 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 acquired from the Dutch in Dejima.
Image:KunitomoAirGunMechanism.jpg|thumb|Kunitomo air gun trigger mechanism
The Lewis and Clark Expedition carried a reservoir air gun, very likely the Girardoni, as it held 22.46 caliber round balls in a tubular magazine mounted on the side of the barrel. The butt served as the air reservoir and had a working pressure of. The rifle was said to be capable of 22 aimed shots per minute and had a rifled bore of and a groove diameter.
One of the first commercially successful and mass-produced air guns was manufactured by the William F. Markham's Markham Air Rifle Company in Plymouth, Michigan, US. Their first model air gun was the wooden Challenger, marketed in 1886. In response, Clarence Hamilton from the neighboring Plymouth Air Rifle Company marketed their all-metal Daisy BB Gun in early 1888, which prompted Markham to respond with their Chicago model in 1888 followed by the King model in 1890. The Chicago model was sold by Sears, Roebuck for 73 cents in its catalog. In 1928, the name of the Markham company was changed to King Air Rifle Company after the company was purchased by Daisy in 1916 after decades of intense competition, and continued to manufacture the "King" model air rifle until 1935 before ceasing operation altogether in the 1940s.
From the 1890s onwards, air rifles were used in Birmingham, England for competitive target shooting. Matches were held in public houses and working men's clubs, which sponsored shooting teams. This often took the form of Bell Target shooting, where the competitor aims to ring a bell by shooting through a small hole in a steel plate. Prizes, such as a leg of mutton for the winning team, were paid for by the losing team. During this time, over 4,000 air rifle clubs and associations existed across Great Britain, with as many as 1,600 in Birmingham alone. During this time, the air gun was associated with poaching because it could deliver a shot without a significant muzzle report.
Use
Air guns are used for hunting, pest control, recreational shooting and competitive sports such as the Olympic 10 m air rifle and 10 m air pistol events. Field target is a competitive form of metallic silhouette shooting in which the targets are animal-shaped steel targets with a "kill zone" cut-out. Hunter field target is a variation, using identical equipment, but with differing rules. The distances FT and HFT competitions are shot at range between for HFT & for FT, with varying sizes of "reducers" being used to increase or decrease the size of the kill zone. In the UK, competition power limits are set at the legal maximum for an unlicensed air rifle, i.e.. Air rifle benchrest is an international shooting sport where the objective is to hit a bulls eye target at shooting distance. There are two divisions ARLV and ARHV.The increasing affordability of higher-power pre-charged pneumatic rifles has allowed large projectiles and further target distance for competition purposes. For instance, the Extreme Benchrest competition held annually in Green Valley, Arizona allows calibers up to at 75 yd while the Big Bore Benchrest arm of the same competition at other localities engages targets at.
Powerplant
The component of an airgun that provides the gas pressure needed to propel projectiles is called its powerplant, which uses internally stored pressurized gas; and compressed gas, which uses external sources of pressurized gas.Spring-piston
A spring-piston air gun operates by means of a spring-loaded piston pump assembly contained within a compression chamber separate from the gun barrel. Traditionally, a grease-lubricated steel coil spring is used as the powerplant main spring. Before shooting, the user needs to manually cock the gun by flexing a lever connected to the pump assembly, which pulls the pump piston rearwards and compresses the main spring until the rear of the piston engages the sear. When shooting, the trigger is pulled and disengages the sear, allowing the main spring to decompress and release its stored elastic potential energy, pushing the piston forward, thereby compressing the air in the pump cylinder. Because the pump outlet is directly behind the pellet seated in the barrel chamber, once the air pressure has risen enough to overcome the static friction and/or barrel restriction holding back the pellet, the pellet is propelled forward by an expanding column of pressurized air. All this takes place in a fraction of a second, during which the air undergoes adiabatic heating to several hundred degrees and then cools as the air expands. This can also cause a phenomenon referred as "dieseling", where flammable substances in the compression chamber can be ignited by the compression heat like in a diesel engine, and lead to an afterburner effect with additional thrusts. This often results in combustion smoke coming out of the muzzle and potential pressure damage to the rubber O-ring seals inside the gun. Dieseling can be made to occur intentionally to increase power, by coating the pellet with lubricant or petroleum jelly, although this may result in damage to the breech seal.Most spring-piston guns are single-shot breechloaders by nature, but multiple-shot repeaters with magazine feeders have been introduced in recent years by manufacturers such as Gamo, Umarex and Hatsan.
Spring-piston guns, especially the high-powered "magnum" guns, are able to achieve muzzle velocities exceeding the speed of sound. The effort required for the cocking stroke is proportional to the designed power of the gun, with higher muzzle velocities requiring a stiffer spring and hence a greater cocking effort. Spring-piston guns have a practical upper limit of for.177 cal pellets, as higher velocities cause unstable pellet flight and loss of accuracy. This is due to the extreme buffeting caused when the pellet reaches and surpasses transonic speed, then slows back down and goes through sound barrier again, which is more than enough to destabilize the pellet's flight. Shortly after leaving the barrel, the supersonic pellet falls back below the speed of sound and the shock wave overtakes the pellet, causing its flight stability to be disrupted. Drag increases disproportionately as pellet velocity increases, so it is generally better to increase pellet weight to keep velocities subsonic in high-powered guns. Many shooters find that velocities in the range offer an ideal balance between power and accuracy.
Spring guns are typically cocked by one of the following mechanisms:
- Break-barrel — like a break action firearm, the barrel is hinged at the junction with the receiver and is flexed downwards to expose the breech and serves as the cocking lever
- Fixed-barrel – the barrel is fixed to the receiver, and the cocking is done with a separate cocking lever
- * Underlever – the cocking lever is located underneath the barrel or the receiver and is flexed downwards during cocking
- * Sidelever – the cocking lever is located to the side of the receiver and is flexed sideways during cocking
- * Overlever – the cocking lever is located above the barrel and is flexed upwards during cocking, seen in some air pistols
- Motorized cocking powered by a rechargeable battery
The better quality spring guns can have very long service lives, being simple to maintain and repair. Because they deliver the same mechanical energy output on each shot, external ballistics are quite consistent. Most Olympic air gun competitions through the 1970s and into the 1980s were shot with spring-piston guns, often of the opposing-piston recoil-eliminating type. Beginning in the 1980s, guns powered by compressed/liquefied carbon dioxide began to dominate the competition. Today, the guns used at the highest levels of competition are powered by compressed air.