Catapult, aka Slingshot or "Bean Shooter"

[CharlesHarris]

There is a YouTube video of the German fellow injuring hjmself when a large ballbearing rebounded off a champagne bottle and struck him.in the forehead. Fortunately the gentleman had the thick skull and sloped forehead of his Neanderthal ancestors, and while he was obviously in great pain and bled heavily, the glancing blow saved his life. Had it struck an inch or so lower he may have been killed.

The moral, fire test shots through a barricade and wear a riot helmet with full facial impact protection!