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.