I wonder if any of the artistes who wrote a note or made a drawing ever wondered about the odds of being injured or killed by an enemy picking up the 'bullet' he'd just flung and flinging it back.
We could be using "Struck by his own bullet" instead of "Hoist by his own petard"... I wonder how big Boner's petard is???
A sling (not slingshot) is serious missile launching apparatus. Modern Biblical "scholars" dismiss the story of David taking down Goliath, but as a mid-adolescent with lots of free time to practice in the pastures he was probably very accomplished. Ancient Samaritans used ranks of slingmen. Like Crucifixtion and so many deadly skills, the Romans adapted practices from all over their empire and perfected them.