There are legal issues in airsoft as well as several rules imposed in a game by game basis. Most indoor airsoft fields only allow up to 350 ft/s (110 m/s), and most outdoor fields begin capping near the 410 ft/s for rifles and 525 ft/s for long-range guns such as sniper rifles. Most outdoor fields also impose a minimum engagement distance for guns firing over a certain range, normally for squad support weapons and sniper rifles. In order for an airsoft gun to cause any serious injury, it would have to be well over these limits and in close proximity.
To even reach such speeds, the gun would have to be highly modified. So it is therefore unlikely to cause permanent or serious damage with any stock airsoft gun. The use of metallic BBs, or any foreign objects, is very dangerous for the user and other people and property in close vicinity, and may damage the airsoft gun as well. However, specially designed and built metallic 6 mm BBs for airsoft guns can be found on the market. These metallic BBs should not be used for airsoft play because they can break through goggles and other safety gear. How Ever Plastic bbs Can be a mixture of PLA and Plastic causing less damage to persons.