Air guns are, as a general rule, guns which use some mechanism involving air or carbon dioxide to launch a projectile at a target. Air guns can be used for much the same purposes as firearms, but usually at shorter ranges. They tend to be popular in jurisdictions such as the United Kingdom and parts of Europe, where actual firearms are heavily restricted or banned outright.

Despite similarities in name, Air guns are not the same as [[https://tvtropes.org/pmwiki/pmwiki.php/UsefulNotes/Airsoft Airsoft]]. And despite similarities with firearms, Air guns have several distinct differences in use and engineering that seem counter-intuitive to people familiar with firearms. Spring powered air guns, for example, despite very light felt recoil to the shooter, will beat even top-end rifle scopes apart due to the piston slamming forward against the stop.

Within Air guns, there's a sharp difference between less expensive BB Guns and more expensive Air Rifles. BB Guns tend to be like the Red Ryder Carbine of ''Film/AChristmasStory'', and considered similar to a particularly dangerous toy. More serious air guns are capable of consistently taking small game, with higher-end, large bore air rifles being fully capable of taking medium to large game at short ranges. Furthermore, there is an active, if elderly, air gun competition shooting community.

!'''Ammunition'''
Air guns can use two different types of ammunition, BB's and pellets. BB's are named after a standard shot size, as used in shotguns, and are round balls typically made of steel approximately 4.5mm in diameter, or .177 caliber. Because they are made of steel, they are both incredibly cheap, and bad to be used in rifled barrels- the hard steel damages rifling grooves and does not deform to have spin imparted on it. This significantly limits the accuracy potential of a BB gun. Pellets are shaped somewhat like a small shuttlecock made of metal, usually made of lead, but also often an alloy. Alloy pellets may be used for ballistic reasons, or to comply with local hunting laws requiring non-toxic ammunition. The soft material of pellets and a hollow in the base or skirt of the pellet allow it to expand against the rifling in a barrel for increased accuracy and power retention compared to round steel BB's. Pellets are available in several calibers, with .177 and .22 being the most popular, with .25, .45 and .50 holding on to niche popularity.

!'''Types of air guns'''
* Spring-powered: Use a spring to compress the air. Almost always single-shot, but there are exceptions. Often referred to as recoiling for competitions.
** Break-Barrel: The barrel is swung downwards to load the round.
*** Gas Ram: Typically a Break-Barrel, these use a compressible gas in a sealed piston rather than a mechanical spring.
** Under-lever: A lever under the barrel cocks the spring and opens the chamber.
** Lever-action: Replicas of Winchester-type lever-action rifles.
* Pneumatic: Has an air reservoir that is manually pumped. Most commonly a BB gun.
* PCP (Pre-Charged Pnuematic): These air guns use a tank of compressed air to fire the pellet (and it is always a pellet with a PCP). Typically the most expensive, accurate, and powerful type of air gun.
* CO[[subscript:2]]: Similar to the above, but uses a canister of CO[[subscript:2]] instead. Generally intermediate in power. These are often used in gas-blowback mechanisms, which use the CO[[subscript:2]] to imitate a semi-automatic pistol or rifle.

!'''Air gun laws'''
* In the UK, where air guns are more popular than real firearms, they do not (usually – see below) require a license but can only be purchased from a registered firearms dealer by someone aged 18 or over and their use is subject to similar laws as real firearms: air rifles with a power above 12ft/lb or 16.3J require an FAC (Firearms Certificate) to own, and air pistols over 6ft/lb or 8.1J are banned outright. Plans to implement a license for air guns were proposed in Scotland.
* The US: Areas that have tight restrictions on firearms are likely to be more lenient when it comes to air guns. Just in case, however, ask the local police or your lawyer for advice, but beware: many states' definitions of firearms ''do'' include air guns, even if it's rarely enforced as such. Look for the words pneumatic and calibers down to .177/4.5mm. It probably will never be an issue if you're not doing anything stupid, but it's worth keeping in mind. New Jersey is a major exception to this, with some air rifles even fitting the state's definition of "assault weapon".
* In Brazil, power generally isn't a concern, but any air gun chambered for a caliber larger than 6mm (such as .25) needs a license to own.
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