An air gun can be defined in more than one way, either by standard definition or in legal terms. The standard definition is any gun that requires compressed gas or air to fire a projectile. In legal terms, the definition varies by location.
Many countries consider an air gun to be a firearm. There are different classes of firearms, but in many areas, it is illegal to own an air gun without going through the same processes required to own any other type of firearm. There are usually age restrictions as well. Where guns are prohibited entirely, air guns are generally also banned.
The regulations applied to an air gun usually correspond with the power of the gun. The more powerful it is the more likely it is to be restricted or banned, even though many of the guns available today are not as powerful as those used in the past for defense or hunting. While many people don’t consider an air gun a serious weapon, it can be. Pellet guns and BB guns can cause serious injury. An air gun, like any other gun, must be used responsibly.
There are three basic ways that firearms such as air pistols and air rifles obtain power. They use carbon dioxide, spring pistons, or pneumatics to propel ammunition. Some require cocking or pumping before pulling the trigger, others do not.
The carbon dioxide, or CO2, models do not need to be cocked before pulling the trigger. They do require containers of CO2, which means operating them is somewhat more costly. Because CO2 is sensitive to heat, the containers must be stored at an appropriate temperature, below 120 degrees Fahrenheit or 49 degrees Celsius, but preferably even less. While CO2 designs are not usually as powerful as the other types, they have a simpler construction and can be fired more quickly, storing power to allow repeat firing.
A spring piston air rifle must be cocked before firing. The spring is compressed during cocking and decompressed once the trigger is pulled. This action causes the air behind the projectile to become pressurized, which in turn forcefully ejects the ammunition.
There is more than one type of pneumatic air gun. There is the single stroke design and the multi-stroke. A single stroke air rifle need only be cocked. Multi-stroke styles must be pumped. Minimal pumping allows enough pressure for short-range shoots, while for longer ranges more pumping is required to create enough air pressure.