Many, many years ago, I worked my way through college as a machinist at a small job shop that made automotive manufacturing screw feeders. We received a job to make feeders for small rubber ball bearings. The rubber ball bearings came in two sizes, one about 3/8", and one about 1/4". To help us develop the feeders, the company we were making the feeders for sent us two, 5 gallon-sized boxes of each sized rubber ball bearings. It didn't take but a few days for someone to figure out that a tube, attached to an air hose, would shoot those bearings hard enough to give someone quite a welt, all the way across the shop. Other guys figured out that if you used 2 tubes connected at right angles, and filled one tube with the ball bearings while the other tube was connected to an air hose, that you would have a pretty good ball bearing machine gun. In a matter of a week, the foreman (who was also the lead "ball bearing machine gun maker") called the company we were making the feeders for, and requested two refrigerator-sized boxes of the ball bearings, for "further testing". It wasn't safe to walk around the job shop for months!