Foot lbs penetrate skin
My guess is most of the "toy" BB guns are designed to keep their power below what would penetrate skin. I'd say anything below fps or so.
28 Jul Is the measure of a bullet accurately depicted in foot-pounds of energy? because it lacked the energy to penetrate the skin a second time.
Description:Anybody who has tried an atlatl and dart knows that it's a powerful combination ancient people used it to hunt mammoth, after all. But nobody ever seems to know exactly HOW powerful it is -- on the internet, you will find pages that say it's anywhere from 3 times to times more powerful than a spear thrown by hand. That's a lot of difference, and nobody ever says or shows how they came by their figure.