Airsoft Rifles can be split into groups. Battery powered or Automatic Electric Guns sometimes known as AEG. Gas Powered rifles. Spring Powered mostly sniper rifles.
Electric airsoft rifles or AEG have a piston which is powered by motors, gear box and batteries. The batteries are rechargeable types and mostly Lipo batteries. Most Airsoft rifles have different modes such as single fire or automatic and other combinations depending on model. These guns often fire the pellets or BB's at speeds up to around ( in UK) 350 feet per second with sniper rifles limited to 500 feet per second. On automatic they can fire 90 to 1000 rounds per minute and some models even higher rates. The AEGs first appeared in Japan by a company known as TOKIO MARUI in Japan and the Japanese company Tokyo Marui.
There are now many manufacturers on the market and most of the Electric Guns is by far the most sought after gun and it has good reason to be the most popular. It can be more expensive than the spring loaded if you do not count the sniper rifles. They are made by a vast range of manufacturers and are mostly run off a lipo battery. The battery powers an electric motor with a gear box that fires a piston to blast air through a small space and this in turn pushes out a pellet at speeds or around 300 ft per second and upwards. They can be fired on a fully automatic mode and bb's can be poured out at fantastic rates of fire. A single shot mode can also be selected if required. They are very realistic and this is why they are so popular.
Gas Blow Back.
An other type of airsoft rifle is the the gas powered guns. These are usually made for more advanced players and can still be expensive as some have realistic recoil systems and it gives a very realistic feel. This type is a gas blow back and use green gas for propulsion which fires the bb. The slide will recoil back giving the recoil. The gas can be stored in a magazine or have a special reservoir to hold the gas.. This is a great gun when they are working well but can be expensive to run on gas and prone to sticking in cold weather.
The third type of gun is the spring powered Airsoft gun.They work by cocking back the spring and firing and cocking again to fire a single shot. These guns are usually cheap but some expensive sniper rifles use the sprint system are usually trouble free and very cheap to run. See Airsoft pistols