On 04/11/2020 10:09, The Natural Philosopher wrote:
My friend made a ball bearing cannon - steel tube on a block with a
banger contents inside it. A quite snug fitting ball bearing was tamped
on top and some Jetex fuse was inserted into a breech hole. We aimed it
at the cast metal sign on the side of a tennis court, that ended up with
a neat 1/4" hole in it. It was never fired again...

Or simply hit with a hammer at an incorrect angle the head of the pin of
a cable clip . Chances are it will break off and fly. It has a lot of
energy and will bury itself in the flesh of any unfortunate passer-by.
Always wear safety glasses.

Bill