I got involved on the build to bring in some safety, so I insisted it was fired from a safe distance via a remote control made from old toy radio controlled cars. The cannon was positioned straight up as we didnt want the bullet (Which was about the weight of an apple or orange) to stray too far. We also wanted to have our bullet back as we didnt want to keep making them!
We fired it from our safe distance. We heard the sound but didnt see the bullet leave the cannon. My brother was going to run to the cannon but I stopped him. I counted to ten slowly and then we walked over to it to see if the bullet was lodged in the cannon. We were there for about five seconds looking down the empty barrel and bang! The bullet came down right behind us less then two feet from us.
On each try the same happened. Took something like 15-20 seconds to return and despite the wind, it returned within the area of the cannon straying no further then at most 10 feet! We had a few close ones as we assumed it couldn't possibly take any longer then it did to return. It didnt have a parachute effect as it was made without this in mind.
I'm not going to give details on how it was made other then the radio controlled parts because a dare say one could do some damage if it didnt go to plan. I'm glad I got involved as though I tried to talk him out of it he was determined to try, so I was in between my mum who put pressure on me to ensure his safety and my brother who would do it anyway!
It was an experience. Not sure how high it went though except to say it went through the clouds, hence why we could not see it, apart from the speed it left the cannon.