What you guys are missing here is those projectiles are filled with Bismuth. The FN303 projectile weighs 8 grams and is fired at 300 fps. A standard PB weighs only 2 grams and is fired at 300 fps.
The 303 will shoot clear through 1/2 plywood. Before it was toned down to get to the "less lethal" power level, 2 or 3 sheets of 3/4 was not sufficient for a backstop.
As far as the military requirements go, it was destructively tested the same way an assault rifle is, and passed.
I'd tell you how I know, but then I'd have to kill you.
