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.
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
The electric guns were run on NiMH batteries but have become less important over the past few years with the improvement in LIPO batteries.Manufactures have improved the guns to take the extra power that these batteries generate. The modern replica is so realistic that from a short distance it would be difficult to tell the difference for a real one with metal bodies and strong plastics that make Airsoft guns look and feel very realistic. Some manufactures such as Tokio Marui, G&G and ARES have taken this to a new level and some have full metal bodies. Of course this adds greatly to the fun. 3 common AEGs are the AR-15 series like the M16 rifle, M4 etc or colt series and not forgetting the AK and G36 styles, Every year the range grows and grows with nearly all the real steel version now being made for the outdoor gaming industry Spare parts and upgrades available for these replicas. Modern guns are :-