Crazy slingshot guy Joerg Sprave did it:
LOL this guy sure can whip up homebrew guns quick. Sure most of them are very rough looking, but they all seem to work well so who cares? It’s just a real shame he hasn’t moved to the US yet and made an actual business out of his talent yet.
Starting at 4:52 he uses a rubber band powered press thing he made to set off some blank ammunition.