Heres some History
The history of "airsoft" originated in Japan during the mid-1970s, mainly because it was illegal to own firearms by private individuals. The first airsoft guns available were spring-powered replicas of firearms that fired 6mm, plastic pellets or BBs. The gun then spread to China, Hong Kong, Korea, Taiwan and the Philippines and became very popular chiefly because of firearm restrictions in these countries.
The first airsoft guns were those air driven pellet guns, cap-type guns and spring driven pellet guns. The early Japanese air driven pellet guns were based on semi-automatic pistols. They were spring powered. The plastic pellet was propelled by air when the spring piston was released. In the cap-type guns, powerful an explosive cap was used to make the sound of gunfire and to eject the spent cartridge. In spring driven pellet guns, a spring was used to propel the pellet held between two small locks and released when the gun was fired.