I just "fired" a 3/8" steel ball at a piece of 1/2" sheet rock at 3 feet distance with a slingshot. The first went about half way through and bounced back. The second went half way through, and was embedded. Velocity would be about 200 plus FPS. Maybe my old wrist rocket would have penetrated, not sure, but now I have a wimpy old mans slingshot. I am as sure as I can be that the same projectile would not penetrate human skin, but my wife was not game to try! I know from prior experience that a target arrow shot out of a 25 lb bow will easily penetrate sheetrock. I don't think it would do much on a human target, other than hurt.

Best,
Rick