The strongest Airsoft Rifles that I know of are the following:
Spring Rifle: 500 fps - WELL MB05 AWM APS2 Airsoft Sniper Rifle
Electric Rifle: 550 fps - Systema Training Weapon M4A1 M4 PTW MAX 420 fps - G&G GR25 SPR
Airsoft Electric Gun Rifle
Gas Rifle: 500 - 550 fps - KJW M700 Police Airsoft Sniper Gas Rifle
I don't no about spring, but the Green Gas M700 Sniper Rifle Competition Professional Airsoft gun, has 720-FPS!!!! And the, Spring CSI L96 Bolt Action Airsoft Sniper Rifle, has 550-FPS. They are both from, Hobby Tron.com
About 1000 fps for a pre-charged pneumatic, such as the Evanix.
No such law
The answer to your question is up to 275 fps. ( Feet per sec. ) For more info on this airsoft pistol see related links.
That would most likely be the Hatsan AT P2 PCP Air Pistol at 870 FPS
The highest velocity of an airgun is that of Evanix AR6 pistol which is 1000 fps.
No. It's actually quite slow. Most high-end guns shoot about 400+ FPS
the best way to lower the fps on a sniper rifle would be to reduce the type of spring you are using. airsplat.com has a whole bunch to pick from to decide what type of FPS you're looking for.
The best airsoft spring pistol for young kids are guns that aren't extremely powerful, I'd suggest this gun which is at 235 fps, others will feel it but it won't hurt too bad. This gun may be purchased from Hobby Tron at hobbytron.com/AirsoftGuns.html, this is the title of the gun 'Sprind Tactical TMP Machine Pistol FPS-235 Electril Sight, Silencer, Flashlight Airsoft Gun' also, this guns runs around $15.95.
6 mm
280 fps
Gamo Hunter Extreme 1650 FPS - Air rifle .177 Cal Air Force TalonP 900 FPS air pistol .25 Cal Hatsan AT P1 Air Pistol .177 870 FPS The Air Force TalonP is faster in .25 Cal than the Hatsan .177 Cal