Air Pistol Basics
An air gun is a pneumatic gun that uses compressed air or other high pressure gas as a propellant to shoot projectiles.
The modern air gun is generally low powered due to safety regulations and legal restrictions. However, they can drive a pellet at a speed exceeding 330 m/s which is almost the speed of sound. While many of the low powered air guns can be securely fired in a garden, it is illegal in many countries to discharge them in residential areas. They are very accurate, though, and are used in the Olympic Games.
There are several different methods of powering an air gun. The methods used for powering an air gun can be broken down into thee general classifications: spring piston, pneumatic and Co2.
Spring Piston
You only need to cock the spring piston air gun once to achieve a muzzle velocity that is very near the speed of sound. With air guns you cock the gun to increase the power with higher velocities. Each cocking stroke increases the power; however, each stroke requires more effort than the previous stroke.
A spring piston gun operates with a piston that is, like its name implies, spring loaded. It is contained within a compression chamber. When you cock the gun, the spring is compressed further and further until a small hook engages the sear. When you pull the trigger, the hook releases the sear and a chain reaction follows where the spring is decompressed, pushing the piston forward, compressing the air. When the air pressure increases to the level that it is able to overcome friction, it propels the pellet forward.
The downside of a spring gun is that they have a rather large recoil and spring vibration. You can control the vibrations, though, if you have your gun tuned by an air gun smith, or you use a spring guide.
Pneumatic
The energy source of a pneumatic air gun is pre-compressed air. Guns that are single stroke and multi stroke use a pump to pressurize the air. A high pressure hand pump (reaching pressures of 300 bars) is used to fill the reservoirs. Transferring air from a diving cylinder is also an effective way to fill the reservoirs. This means that there are no significant movements of heavy parts so the recoil is a "true recoil."
Air guns that are multi stroke require as few as 2 or as many as 10 pumps to store the compressed air. It is through this method that variable power is possible, allowing you to modify the power for different shooting ranges. Higher quality air rifles have the ability to shoot at speeds of more than 1000 fps.
Alternatively, a single stroke gun requires just one motion of the cocking lever to sufficiently compress the air. Target rifles and pistols generally use the single pump system because the higher energy that comes from the multi stroke is not necessary.
A pre-charged pneumatic, or PCP, air gun can be used for hunting and for competition Due to the cylinders or the charging systems, PCP guns are a little more costly to purchase, but their operating costs are significantly lower than a Co2 gun
Co2
The majority of the Co2 guns employ the use of a cylinder that is disposable and pre filled with 12 grams of liquefied Co2 Some more expensive models feature larger Co2 reservoirs that are also refillable.
There are two key advantages to the Co2 air gun over the pre charged guns
1. There is only a small amount of liquid that converts to a large amount of pressurized gas.
2. There is no pressure regulator.