Paintball markers are proper weapons
None of your air-softy bullshit.
Legal restrictions on air rifles limit the maximum fps of a standard paintball to 300, and to be honest if you tried to fire one at a higher velocity they would mostly just explode in the barrel.
There are also electronic triggers out there that allow certain combinations of trigger-press to put them into full-auto mode (usually at a rate of around 15 balls per second).
All of which is limited by the fact that a paintball is very *soft*. They have the ability to fire other types of projectile, ones that wouldn't explode at higher than 300fps. Doing that would make them firearms, and since they wouldn't be recognised as such there is no chance of adding one to your licence, so very illegal whichever way you want to cut it.
However, the limits of the paintball markers themselves go way above 300fps.
I don't know what kind of energy a 0.68" nylon bearing fired at 500 fps would have*, but with 15 of them coming at you every second (and a hopper that holds 250 them) you can see that they have a lot more potential than air-soft.
*Turns out to be roughly 188 ft-lb/255 Joule