I suspect that your windsheild was popped with a pellet gun. Upgrading an AEG to the point of piercing glass isn't that easy. It takes a heck of a spring to push a pellet through automotive glass. I'm guessing the only easy ASG to use to bust windows is the KJW M700. On propane it can push just over 500fps w' 0.43g pellets without modification. Conversely pretty much any Crappy tire pellet gun can damage windows.
And registration on ASGs?! Wouldn't be practical with all the chop shopping going on. It's not hard enough to open up a mechbox and put in super torque up gears and a heavy spring. Sell your stock plastic body and upgrade to a metal one and your registration goes with someone else.
The 3.5j/cm^2 limitation is an interesting way to limit projectile energy. I initially thought that someone could obey the limitation and shoot larger projectiles and deliver a dangerous hit. Crank up the frontal area so you can deliver more energy but meet the energy/area limitation. On closer inspection it actually gets less harmless as you increase projectile size.
If you scale up a pellet, the frontal area increases by the square of the diameter, but the volume increases even further (by the cubic). That means if you double a pellet's size, you quadruple the frontal area and therefore quadruple how much energy you can impart to the pellet. Sounds bad, but you also octuple (8x) the pellets mass so the velocity of the pellet actually decreases by about 30% (1/sqrt2).
So if you were at the energy limit and were shooting 6mm 0.2g pellets you'd hit 333fps. If you shot 12mm 1.6g phat pellets, you have to be shooting 233fps to be at the energy/area limits which is actually not too far off from what is determined to be a safe paintball velocity.
It's a very complete specification really. It even anticapates shaft projectiles like arrows. Arrows have small frontal area so you're not allowed to pack much energy into them. Furthermore, they're heavy so that bit of energy doesn't result in very high flight velocities. Probably makes them completely useless actually. Japan has some love of ceremonial archery. I'm guessing they'll allow it because it's not too amenable to drive by arrowings. You'd need a convertible so you could stand up and clear the limbs. You also only get one shot.
The specification does not appear to limit total discharge energy so I guess moscarts and shotguns are ok as long as the individual projecticles don't exceed 1j each.
Want nearly free GBB gas?