If you ever watch Mythbusters you know that ballistic gelatin is very close the same density as human files. Therefore, when you hit the gelatin with certain weapons you can see how much damage it would do to a person. Slingshot madman Joerg Sprave is back at it again and this time he has a bunch of marbles that he is using for ammo.
Sprave uses three different marble sizes for his test and finds that they penetrate the gelatin very impressively. He also uses a small lead ball as a comparison. That lead ball zips all the way though the gelatin. Just think of these things fired at some hapless zombie's tummy. The marbles are made from glass.
Naturally, Sprave fires the marbles at a rock and a wall just to see if the marbles will shatter. The marbles stay in one piece, but they do take chucks out of the rock. Check out the video to see the marble shooting action.