http://www.liveleak.com/view?i=cf4_1414026047
I like that video!
We have a tradition at new year of shooting with calcium carbide in 6 gallon milk barrels (used until the seventies).
This tradition got a bit out of hand, so now the young guys build their own guns.
Normally they are fired with something glowing on the end of a stick.
I made an electric ignition form a motorcycle ignition coil for my son once (thought that was safer).
Here you can see why:
https://www.youtube.com/watch?v=IEnNv1RyYf8
About 1/2 as loud as the oxy/propane cannon. With the cutting torch and the bottom 1/2 of our engine hoist we fired soft baseballs up onto the side of a mountain and they would roll into a ravine and all the way back down where we would fire them again. Someone got bored waiting for the balls to come down and fired a large rock which started a bit of an avalanche so we stopped doing that.