Laws on black powder cannons?

A. Hello Keith. This is a metal finishing website, so you need to be talking to a lawyer, not to us.

But since your posting is here, an anecdote may help:
I was serving on the grand jury, and possession of a BB gun was a common felony charge. I spent every Monday in court for 16 weeks, and the prosecutor sought and got *felony* indictments on this charge several times every day.

Then one afternoon during this stint, my son & a friend are playing outside, and another kid shoots them with a BB gun. No real harm done, but the friend is whining that he was hit, so I confiscate the BB gun and call the police to get rid of it. The dispatcher says (paraphrasing): "If the kid misused it, keep it". I say I don't want it. He says "Okay, sir, put it in your garbage." I say no firearms in my garbage. So he tells me "You can drop it off at the station." I say I'm not driving with a BB gun in my car, please send an officer to pick it up: "It's a TOY, sir, it's NOT a GUN! It's just a TOY!".

The point being that in my state a BB gun is laughed off as a toy except if they want a cudgel to use to make you plead guilty to something (maybe a spouse called 911 about domestic abuse then refused to prosecute)? So they hold a FELONY indictment over you (penitentiary time) -- a situation that gives prosecutors outrageous power to force you to plead guilty to anything they wish.

I can't say that a cannon in your state is exactly analogous to a BB gun in mine, but a lawyer may be able to instantly do more for you than you can imagine. Call him/her immediately because your life is in the hands of someone who can ruin it on a whim so you don't want to tweak him/her. Good luck.