Originally Posted by Ricochet
Thanks hitman, I'll have to double check my facts. If that is indeed the case, then a person could go around 0.45g BB traveling at 525 FPS, for it to be considered a firearm. Approx: 5.7j. My understanding is it is one or the other due to the ability to get around it. Can you imagine the speed of a 1.5g BB it would take to hit 5.7j? So if a person brought a 1.5g BB up to 900 FPS, their Kinetic Energy would be 5.644j. That would be quite dangerous. And a 0.30g BB traveling at 625 FPS would be 5.444j. Both then would not technically be a firearm. I thought the idea was to cover on both ends, so someone couldn't do that. But I will double check.
You've got your maths wrong; or at least have a coma at the wrong place or something:
a 1.5g projectile at 900 fps would equate to 56.44 joules, which is about a 1/10 of a 9x19mm bullet. Pretty scary for playing :P
.3g at 625fps = 6.349 joules, still rated as a firearm
Here's a nice tool to do all these calculations: www.wolframalpha.com
(and much much much other useful things)