As a kid I made one with a 4 foot length of copper plumbing pipe; made darts from nails that I hammered and filed into little 'arrowhead' type points and were fastened into little dowels, a wad of kleenex on the other end to seal the pipe.
Slid the first dart into the pipe and went to try it out. With a bit of practice it wasn't hard to be accurate up to about 25 feet or so, so I went 'hunting'. First shot at a starling and the dart went right through it
. I was pretty proud of myself
Then I found out it was an illegal weapon
Still don't know why. It would be fun and effective to use on grouse.