The slower BB guns put out 3-5 ft-lbs of energy. You need to achieve 350fps/106m/s with a .177 BB in order for it to be considered dangerous. That's over 4J of energy, about 3-4x what most airsoft guns shoot. Considering this is for target BB guns, any BB/pellet gun meant for hunting needs considerably more energy to be lethal to small game. Consider that one of the highest velocities capable on an airsoft gun is 600 fps on the WA-2000 (an extremely rare GAS gun). Even at that, the energy output is only 3.3J. You see where I'm going with this? To acheive 3.3J with a spring is nigh on impossible and only high end sniper rifles are even capable of getting close, but you're looking to spend a ton of money even getting there. To acheive a lethal terminal velocity with that muzzle veolcity, you'd have to do a point blank shot. Why go to all this trouble when BB guns are readily obtainable and less of a hassle and already shooting hot enough? I just don't get why you're arguing the lethality of an airsoft gun since it's such a a rarity/improbability and not as simple as "some idiot loading copper BB's". If we're gonna talk sheer possibility here, it's probably more likely you'll get struck by lightning in the field or impale yourself on your gun. And real steel at an airsoft game is a completely unrelated issue since 99% of the time we chrono beforehand. If someone is so intent on harming people, airsoft is more of a hassle than its worth. Are you trying to argue how lethal airsoft is?