The first cannon I built was machined from a 3" dia. 24" long hollow 4340 compressor stud 1" bore. First test fire was 1-3/4 oz. ffg and a wadded up dry brown paper shop towel rammed down tight with a broomstick. All this transpired in our welding shop, at the urging of our Cajun machinist, with no carriage, I just sat it in a short wooden box backed up against the wall and aimed at the opposite cinder block wall across the shop. Closing all the doors, with the boss gone to lunch, we touched that baby off, 20+ years of welding dust and cobwebs came raining down for a good five minutes, and 1-3/4 oz. of ffg BP smoke inundated the shop. We, having not thought ahead, immediately switched on all the exhaust fans and opened all doors to air out the shop. We had just opened the big bay door and were discussing the test results and aftermath when a police car came idling down the street. Seeing us all out front he stopped to make inquiries. Yes sir, we did hear a rather loud boom. No sir, we are not sure where it came from, we were inside with the doors shut when we heard it. We came out to see if there was any smoke coming from the refinery (main gate 5 blocks down the street). Yes sir, you have a good day, sir. Upon further inspection of the crime scene, a perfectly round 1" diameter 1/4" deep indentation was found in the target wall