Originally Posted by xmms
I think an airsoft gun with 500+ FPS would be considered as a restricted firearm.
And you would be wrong.
It's not about velocity. It's about muzzle energy. Energy is the product of velocity and mass of the projectile.
In order for a 0.2g airsoft projectile to reach the energy required to turn it into a controlled / restricted / prohibited firearm, it has to shoot in the area of 770-ish fps (can't remember the exact velocity, but it's around there).
So as Drake said, please refrain from giving advice if you don't know what you're talking about. Noobs that don't know what they're talking about are the reason that misinformation spreads the way it does.