[RonF]

Many years ago, I observed an enterprising young man who had cut the tops and bottoms off of about 5 soda cans. He duct taped them togetehr end-to-end, and duct taped an empty but otherwise unmodfified can on the bottom. He punched a hole in the bottom, dropped a tennis ball into the top, shot lighter fluid into the bottom can and lit the hole.

The ball went about 50 yards. My across-the-street neighbor happened to be out in his front yard mowing the lawn on his rider mower, oblivious to all this. I didn't like him. I offered the young man $5.00 (this is back in ~1972) to see if he could get him.

The kid found the range in 3 shots. It was worth every penny.

[Gun142]

LOL
That's pretty good.

Best we did was shoot marker caps through EMT pipe [conduit] with 'lady fingers' (mini-firecrackers).

[Physicist]

Oh, yeah, I used to do that when I was in the Boy Scouts. What makes it work so well is that the cans are extremely smooth inside, and a tennis ball fits almost perfectly (the fuzz makes just the right seal). I'll bet it's hard to make these anymore, now that there's no seam to cut open at the bottom of the can.

[kitchen]

We used to do the tennis ball cannon thing, first with carbide, then switching to lighter fluid for a faster turn around. Then somebody discovered that a bunch of those tiny juice cans made one hell of a golf ball gun. Fortunately no one was ever hit in the noodle.