+1 Indy1919 - I used to be on a NSSA artillery team - both Parrott Rifle AND Mortor. Before we were even allowed to compete, we had to undergo a full inspection of the tube on a regular basis.
When you are talking artillery, you are talking much larger powder loads that rifles/smoothbore long guns. It's fine to make jokes about it and have some humor . . . but I have seen far too many "unsafe practices" being done by those who think they know everything about firing muzzleloading artillery. I'm a firm believer that anyone who shoots BP artillery should go through a certification course on it - not unlike what is required for hunting, etc. by many states. I shot artillery for many years - I have witnessed individuals walking in front of loaded pieces, failure to sponge a bore, failure to thumb a vent while sponging and loading, failure to make sure the limber chest is closed, etc. Yea, accidents never happen . . . but when they do, it's too late. In the 60's I was at an event where there was an artillery accident - it took two lives and caused injury to several others. The cause . . . carelessness and failure to follow rules.
Yes . . . you could have the same thing with "kit" or "custom" guns . . . but hopefully, those pieces have barrels on them that were made by manufacturers who are experienced in making barrels. There are far too many "home made" artillery pieces that are made by folks who have no idea of metallurgy and what is required. How many of them do a inspection of the piece . . . how many of them check for eroded vents and how many of them have taken training on muzzleloading artillery safety/practices?
I don't mean to be a "wet blanket" here and I know that the OP was poking fun with his post . . . but . . . the truth of the matter is . . . a range has the right to set their rules and limitations . . . . and there are reasons for it . . . liability.
If a pair of '51 Navies were good enough for Billy Hickok, then a single Navy on my right hip is good enough for me . . . besides . . . I'm probably only half as good as he was anyways. Hiram's Rangers Badge #63