Editing Air gun (section)

=== Pneumatic ===
[[File:New Benelli Kite.jpg|thumb|An example of a [[Benelli Kite]] pre-charged pneumatic air pistol, as used in [[10 m Air Pistol|10 metre air pistol]] [[ISSF shooting events]]]]
Pneumatic airguns propel the projectiles by utilizing the [[compressed air energy storage|pneumatic potential energy]] within [[compressed air]], which is pressurized beforehand and stored inside the gun, and then released through valves during shooting. Single-stroke and multi-stroke pump guns utilize an on-board [[hand pump]] to pressurize air in an internal [[pressure vessel|reservoir tank]], while pre-charged pneumatic guns' reservoirs are filled from an external source using either a high-pressure [[bicycle pump#Stand pump|stand pump]] or by decanting air from a larger [[diving cylinder]].

====Pump pneumatic====
'''Pump pneumatic air gun'''s, or '''pump gun'''s, use a lever-operated onboard air pump to pressurize an internal reservoir, and then discharge the stored compressed air during shooting. Depending on the design, pump guns can be either single-stroke or multi-stroke.

* In ''single-stroke'' pneumatic air guns (also known as "single pump") a single motion of the cocking lever is all that is required to mechanically compress the air. The single-pump system has always dominated the casual plinking market, and is usually found in target rifles and pistols, where the higher muzzle energy of a multi-stroke pumping system is not required. Single-stroke pneumatic rifles dominated the national and international [[International Shooting Sport Federation|ISSF]] [[ISSF shooting events|10 metre air rifle shooting events]] from the 1970s to the 1990s, until being outperformed by the introduction of pre-charged pneumatic (PCP) guns (discussed [[#Pre-charged pneumatic|below]]).
* ''Multi-stroke'' pneumatic air guns (also known as "multi-pump") use multiple pumpings to achieve variable power levels in order to adapt for both long or short-range shooting. These air guns are usually single-shot, where each shot requires approximately 5 strokes. However, up to five shots are possible, usually requiring approximately 10 to 20 strokes, as long as the air reservoir is capable of storing higher pressure. For safety reasons, most multi-stroke guns are usually designed to have their pump lever jam when the reservoir has reached its maximum pressure limit, so the user can no longer pump the gun until it's discharged. The maximum pressure limit for the reservoir is approximately 20 to 30 strokes.

====Pre-charged pneumatic====
[[Image:20ozCO2Condor.JPG|thumb|Airforce Condor, one of the most powerful PCP air rifles on the market]] 
'''Pre-charged pneumatic air guns''' or '''PCP''' have their internal reservoir pre-filled from an external air source (such as a [[diving cylinder]] or [[air compressor]], or by manual charging with a high-pressure [[bicycle pump#Stand pump|stand pump]]), and remain pressurized until depleted after repeated shooting. During shooting, the hammer strikes the reservoir's release valve, allowing a set volume of the pressurized air to be discharged into the chamber and propel the projectile.  Depending on the release valve design, PCP air guns can be categorized into two types – ''unregulated'' and ''regulated'' (which has either a mechanical or electronic [[pressure regulator|regulator]] valve). In addition to [[compressed air]], custom PCP models using compressed pure [[nitrogen]] and even compressed [[helium]] have also been recently developed.

[[File:Walther LG400 FT England.jpg|thumb|[[Field Target]] variant of a [[Walther LG400]] PCP Air Rifle.]]
Because of the need for cylinders or charging systems, PCP guns have higher initial costs but much lower operating costs when compared to CO<sub>2</sub> rifles, and have superior performance over ordinary pump guns. Having no significant movement of heavy mechanical parts during the discharge cycle, PCP airgun designs produce lower [[recoil]], and can shoot as many as 100 shots per charge depending on the tank/reservoir size. The ready supply of air has allowed the development of semi- and fully automatic air guns.<ref>{{cite web|url=http://air-ordnance.com/smg-22-p-938.html|title=Air Ordnance Full Auto Pellet Gun|access-date=28 November 2014|archive-url=https://web.archive.org/web/20141203213004/http://air-ordnance.com/smg-22-p-938.html|archive-date=3 December 2014|url-status=dead}}</ref> PCP guns are very popular in [[Europe]] because of their accuracy and ease of use. They are widely utilized in [[ISSF shooting events|ISSF 10 meter air pistol and rifle shooting events]] and the sport of [[Field Target]] shooting,<ref>{{cite web|url=http://www.aafta.org|title=American Airgun Field Target Association|access-date=28 November 2014}}</ref> and are usually fitted with [[telescopic sight]]s.

Early stand pump designs encountered problems of fatigue (both human and mechanical), temperature warping, and condensation – none of which are beneficial to accurate shooting or the airguns' longevity. Modern stand pumps have multi-stage chambers and built-in air filtration systems and have overcome many of these problems. Using [[scuba set|scuba]]-quality air decanted from a diving cylinder provides consistently clean, dry, high-pressure air.

During the typical PCP's discharge cycle, the hammer of the rifle is released by the sear to strike the [[bash valve]]. The hammer may move rearwards or forwards, unlike firearms where the hammer almost always moves forward. The valve is held closed by a spring and the pressure of the air in the reservoir. The pressure of the spring is constant, and the pressure of the air released (which is also known as the ''working pressure'') decreases with each successive shot. As a result, when the reservoir pressure is high, the valve opens less fully and closes faster than when the reservoir pressure is lower, resulting in a similar total volume of air flowing past the valve with each shot. This results in a degree of partial self-regulation that gives a greater consistency of velocity from shot to shot, which corresponds to the middle "plateau" phase of the gun's shot-to-shot [[muzzle velocity]] profile (also known as the ''power curve'' ). Well-designed PCP will display good shot-to-shot consistency over a long period, as the air reservoir is being depleted.

Other PCP rifles and pistols are regulated, i.e. the firing valve operates within a secondary chamber separated from the main air reservoir by the regulator body. The regulator maintains the pressure within this secondary chamber at a set pressure (lower than the main reservoir's) until the main reservoir's pressure drops to the point where it can no longer do so.  As a result, shot-to-shot consistency is maintained for longer than in an unregulated rifle, and the gun can also output more shots due to reduced waste of reservoir pressure.<ref>[https://www.researchgate.net/publication/326191398_Internal_Ballistics_of_PCP_Airguns Internal Ballistics of PCP Airguns by Domingo Tavella, August 16, 2018]</ref>