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For the energy source used in reflection seismology, see Air Gun (seismic) . For air guns designed to fire spherical projectiles, see BB Gun . For the Olympic shooting events, see 10 M Air Rifle and 10 M Air Pistol . Xocet, a traditional break barrel, spring-piston air rifle]] An air gun is a Pneumatic Gun which fires projectiles using compressed air or other high pressure gas as a propellant. HISTORY Air guns represent the oldest pneumatic technology having existed since the 15th century. At that time, they presented compelling advantages over the more primitive firearms of the day. For example, air guns could be fired in wet weather (unlike Matchlock s) and with greater rapidity than the Muzzle-loading guns of the period. Moreover, they were quieter than a Firearm of similar Caliber , had no muzzle flash and were completely smokeless, not disclosing the shooter's position on firing. Black powder guns of the 18th and 19th century produced huge volumes of dense smoke on firing, giving air rifles an advantage over them. One might also assume that the sound of an air gun would have been inaudible against the noise of a pitched Battle . For general usage air guns were not a real challenge to the dominant position of powder weapons. They were expensive, delicate, air reservoirs could burst explosively and the valves were not well sealed and slowly leaked pressure. Historical accounts mention common soldiers were often unable to handle the complex guns , this seems logical in an age where the average peasant recruit had never encountered a machine more complex than a horse-drawn cart. People who had any experience with mechanical devices (millers or Clockmaker s) were few and far between. The guns of the period were crude and required little skill by the Infantryman . During this period, France , Austria and other nations had special sniper detachments using air rifles. The Austrian 1780 model was named " Windbüchse " (literally "wind rifle") in German. The guns were developed in 1778 or 1779 ''Arne Hoff, Airguns and Other Pneumatic Arms, Arms & Armour Series, London, 1972'' by the Tyrolese watchmaker, mechanic and gunsmith Bartholomäus Girandoni (1744-1799) and are occasionally referred to as " Girandoni Air Guns " in literature (the name is occasionally spelled "Girandony"; "Giradoni" ''L.Wesley, Air Guns and Air Pistols, London 1955'' or "Girardoni" ''H.L.Blackmore, Hunting Weapons, London 1971''. The Windbüchse (or the Girandoni Air Rifle) was about 4 ft (1.2 m) long and weighed 10 pounds (4.5 kg), which was about the same size and mass as a conventional Musket of the time. The air reservoir was a removable, club-shaped Butt . The Windbüchse carried twenty .51" (13 mm) lead balls in a tubular Magazine . A skilled shooter could unload one magazine in about thirty seconds, which was a fearsome rate of fire compared to the slower muzzle loaders of the period. A shot from this air gun could penetrate a one-inch wooden board at a hundred paces, an effect roughly equal to that of a modern 9 mm or .45" caliber Pistol . , circa 1820-1830.]] Around 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 . Air guns appear throughout other periods of history. The celebrated expedition headed by Lewis And Clark (1804) reportedly carried a .42" (10 mm) reservoir air gun, believed to be produced by Girandoni. It held 22 round balls in a tubular magazine mounted on the side of the Barrel . The butt stock served as the air reservoir and had a working pressure of 800 PSI . The rifle was said to be capable of 22 aimed shots in one minute. During the 1890s, air rifles were used in Birmingham , England for competitive Target Shooting . Competitions were held in, and between, Public House s. Prizes, such as a leg of Mutton for the winning team, were paid for by the losing team. The sport became so popular that just after the turn of the 19th century, a National Air Rifle Association was created. During this time over 4000 air rifle clubs and associations existed across Britain , many of them in Birmingham . During this time, the air gun was associated with Poaching because it could deliver a shot at a relatively quiet level. A modern reproduction of an air cane copied accurately from one in the Royal Armouries, Leeds, UK by Baker and Currie ''Geoffrey Baker & Colin Currie, The Construction and Operation of the Air Gun Vol 2 The Walking Stick Air Gun, privately printed, 2003'' gives a performance of around 480 feet per second (ft/s) for a 51.5 grain 32 calibre lead ball. The reproduction was charged to 600 pounds per square inch and the first shot registered only 272 ft/s, indicating this is a realistic maximum pressure given that the release valve failed to open properly against the high pressure of air in the reservoir. The velocities were reasonably constant for the next five shots, after which they progressively diminished by about 20 ft/s per shot, though this figure is not exact. In an experimental simple home-made large calibre air gun with a three metre barrel Middleton obtained a maximum velocity of 599 ft/s for a 50 calibre 140 grain lead ball, and 411 ft/s from a 2 metre barrel with a .527 calibre 220 grain lead ball, using a pressure of only 100 pounds per square inch pumped with a bicycle pump ''Richard Middleton, The Practical Guide to Man-Powered Bullets, Merlin Unwin Books (UK) and Stackpole Books (US) 2005''. Reilly, a London gunmaker specialising in air guns, writing around 1850 ''E.M.Reilly, Air Guns and other Air Weapons; a short pamphlet reprinted in 1995 by W.S.Curtis Publishers, Rhyl, Clwd'' states that he was able to produce a pressure of a little under 500 pounds per square inch using the direct stroke pump of the time. He does not give muzzle velocities. Wesley (op.cit., pp. 35-6) shot an antique air cane bullet of 3/4 inch diameter into the cast iron fireplace of his workroom, and demolished the fireplace, stripped the wallpaper off the walls, and blew all his oils and chemicals off the mantleshelf. Today's modern air guns are typically low-powered because of safety concerns and legal restrictions; however, high-powered designs are still used for Hunting . These air rifles can propel a Pellet beyond 1100 ft/s (330 m/s), approximately the Speed Of Sound and produce a noise similar to a .22 Caliber Rimfire Rifle . Using very light plastic or alloy pellets, many current spring powered .177 pellet guns can break the sound barrier, and one, the Gamo 1250, can reach 1600 fps with these new pellets. Most low-powered airguns can be safely fired in a backyard or garden, and even indoors, with the proper backstop. In some countries, air guns are still classified as Firearms , and as such it may be illegal to discharge them in residential areas. Air guns can be highly accurate and are used in Target Shooting Events at the Olympic Games , governed by the International Shooting Sport Federation (ISSF). LEGAL ISSUES The legal definition of an air gun differs from country to country; in the United Kingdom , for example, air pistols generating more than 6 Ft·lbf (8.1 J ) or air rifles generating more than 12 ft·lbf (16.2 J) of energy are considered Firearm s, as are air guns in Canada with a muzzle velocity of over 500 ft/s (150 m/s) ''and'' a muzzle energy in excess of 4.2 ft·lbf (5.7 J). In , New York ; Camden and Newark, New Jersey ; Michigan ; Chicago and Morton Grove , Illinois ; San Francisco , California ; and Philadelphia , Pennsylvania . However these states do allow air guns except in these specific cities. Air guns are not considered firearms and are not subject to regulation in most areas; They are slightly more powerful than airsoft guns, and because of their velocity, do not legally require an orange tip. Though they are more powerful, they are in the same class as airsoft, and paintball guns. There are minimum ages for possession, usually 16. Sales of both air guns and ammunition may be restricted in some areas. Some areas may require permits and background checks similar to those required for firearms possession. In the UK, Brocock Air Cartridge System air guns, which use a precharged, single shot air cartridge (similar in size to a .38 Special Cartridge ) were banned after some pistols recovered by the police, were found to have been converted by criminals making them capable of firing Rimfire ammunition or even .38 Special ammunition. BBC News Story In October 2007, a new law will take effect in the UK banning, among other things, the online or mail order sales of air guns. Sales must be made face-to-face. AIR GUN POWER SOURCES There are different methods of powering an air gun. These methods can be broadly divided into 3 groups - spring-piston, gas ram and pneumatic. These methods are used in air rifles and air pistols. Spring-piston Spring-piston air guns are able to achieve muzzle velocities near the Speed Of Sound from a single stroke of a cocking lever or the barrel itself. The difficulty of the cocking stroke is usually related to the power of the gun, with higher muzzle velocities requiring greater cocking effort. Spring-piston guns operate by means of a coiled steel Spring -loaded Piston contained within a compression chamber, and separate from the Barrel . Cocking the gun causes the piston assembly to compress the spring until a small hook on the rear of the piston engages the Sear ; pulling the trigger releases the sear and allows the spring to decompress, pushing the piston forward, thereby compressing the air in the chamber directly behind the pellet. Once the air pressure has risen enough to overcome any static friction and/or barrel restiction holding the pellet, the pellet moves forward, propelled by an expanding column of air. All this takes place in a fraction of a second, during which the air undergoes Adiabatic heating to several hundred degrees during compression, and then cools as the air expands once more. Modern air gun lubricants are generally a compounded mix of ingredients, such as silicone paste and Molybdenum Disulfide . These compounds are designed to not burn at the temperatures reached in airgun compression chambers. Before the availability of synthetic lubricants, when petroleum based products were used, some writers claimed that upwards of 30% of the energy of the shot may have come from the burning or " Diesel ing" of some of the lubricant ''The Airgun from Trigger to Target''. G.V. & G.M. Cardew 1995. 235 pp. Privately published. ISBN 0950510823 - ISBN-13 9780950510828 although this has been debated by others. The use of such combustible lubricants in modern guns, which are much more highly stressed, can severely damage the spring and piston seals. Spring-piston guns seem to have a practical upper limit of 1200 ft/s (370 m/s) for .177 cal (4.5 mm) pellets. Higher velocities cause unstable pellet flight and loss of accuracy. However, the longer lighter pellets can achieve good accuracy and surprising high speed (the Gamo 1250 can reach 1600 fps with their special pellets). Drag increases rapidly as pellets are pushed past the speed of sound, so it is generally better to increase pellet weight to keep velocities subsonic in high-powered guns. Many shooters have found that velocities in the 800 - 900 FPS range offer an ideal balance between power and pellet stability. Most spring piston guns are single-shot breech-loaders by nature (somewhat like a single or double barreled Shotgun ) but multiple-shot guns have been increasingly common in recent years. Spring guns are typically cocked by a mechanism requiring the gun to be hinged at the mid-point (called a break barrel), with the barrel serving as a cocking lever. Other systems that are used include side levers, under-barrel levers, and motorized cocking, powered by a rechargeable battery. Spring guns, especially high-powered ones, have a significant recoil resulting from the forward motion of the piston. Although this recoil is less than that of a cartridge firearm, it can make the gun difficult to shoot accurately as the recoil forces are well under way while the pellet is still traveling down the barrel. Most guns seem to respond well to a light, repeatable grip that allows the gun to vibrate the same way from shot to shot. Spring gun recoil also has a sharp forward component, caused by the piston as it hits the forward end of the chamber when the spring behind it reaches full expansion. This sudden forward acceleration helps to counteract the backward recoil, since the backward and forward recoil forces happen within milliseconds of each other, but it is infamous for knocking around and loosening the lenses and reticles found in low and medium priced Telescopic Sight s, even those which are designed to withstand the (backward-only) recoil from high-powered firearms. On any but the lowest power spring guns, any mounted telescope should be air gun rated. Spring guns can also suffer from spring vibrations that can upset accuracy. These vibrations can be controlled by adding features designed into the gun, like close-fitting spring guides, or by aftermarket tuning done by 'airgunsmiths' who specialize in air gun modifications. A common modification is the addition of viscous silicone grease to the spring, which both lubricates it and damps out vibration. The better quality spring air guns can have long service lives, often exceeding thirty years. Because they deliver the same energy on each shot, the trajectory is extremely consistent. This resulted in most Olympic air gun matches through the 1970s and into the 1980s being shot with spring-piston guns. Beginning in the 1980s, guns powered by compressed, liquefied carbon dioxide began to dominate competition. Today, the guns used at the highest levels of competition are powered by compressed air stored at very high pressures of 2000 to 3000 lbf/in&2 (14 to 21 MPa). The Chinese army uses spring-piston small arms to train more economically. These military-issue Chinese spring-piston air-guns are often available by mail-order, but the buyer should note that quality control on these guns tends to be somewhat variable. Similarly, the Romanian army formerly used spring-piston, single shot, 4.5 mm training rifles to train entry level recruits, prior to switching them to .22 LR training rifles. Some makes of air rifle (e.g. Weihrauch, Theoben) incorporate a gas-ram instead of a mechanical spring. Pressurized air or nitrogen is held in a special chamber built into the piston, and this air is further pressurized when the gun is cocked. It is, in effect, a gas spring more commonly referred to as a "gas-ram" or "gas strut". Gas-ram rifles require higher precision to build, since they require a low friction sliding seal that can withstand the high pressures when cocked. The advantages of the gas-ram include the facility to keep the rifle cocked and ready to fire for long periods of time without harming the mechanism. Also, since there is no spring (and therefore a reduction in moving mass during firing) there is less (although some say slightly sharper), recoil. There is also an elimination of the associated problems of long-term spring fatigue and a faster "lock time" (the time between pulling the trigger and the pellet being discharged). The improvement in lock time makes for better accuracy since there is less time for the gun to move off target. Pneumatic Pneumatic-type airguns require the pre-compression of air in a chamber prior to the gun being used. Single-stroke and multi-stroke guns utilize an on board pump, while PCP guns use either a high-pressure hand pump or air compressor to pressurize the air. When fired, the compressed air in the chamber is used to force the projectile out. Because of this design, the amount of recoil is almost zero as there is no significant movement of mechanical parts during the firing cycle. These air guns may also be powered by CO2 stored in capsules or cylinders, and filled via a hand pump or Dive Tank . Multi-stroke Multi-Stroke pneumatic air guns require 2-10 pumps of an on-board lever to store compressed air within the air gun. Variable power can be achieved through this process, as the user can adapt the power level for long, or short-range shooting. The design of higher quality and match-grade multi-stroke air rifles can propel a pellet to speeds in excess of 1000 feet per second. For beginners and intermediates, multi-stroke air rifles have been a cost-effective choice as they are generally the cheapest form of air gun available. Several manufacturers make multi-stroke air guns including, to name a few, Sheridan, Benjamin, Daisy , and Crosman . Modified multi-pump guns, with stronger pump linkages and improved valves, can produce muzzle energies in excess of 30 foot-pounds from inexpensive guns. Modification kits for Sheridan and Benjamin rifles are available from commercial suppliers. Single-stroke As the name implies, one motion of the cocking lever is all that is needed to compress the air for propulsion. The single-pump system is usually found in target rifles and pistols, where the higher muzzle energy of a multi-stroke pumping system is not required. Pre-charged Pneumatic | ||
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