It’s a real cannon barrel made to order, cast solid and machined out with precision, by those whose job it is to make such things.
And the term ”Proofed’ is used within the terminology of UK legal gun certification and such like. That footage was not of someone testing a homemade device, but of a legally required and recorded part of making a new gun. Being cannon they kinda demand more space than your average proofing house, thus the field J
It will have been thoroughly checked out before and after the ”Proofing shot’, which is normally twice the designed load and yet still within what the barrel should theoretically take. Yet if there was a flaw in the barrel the proofing shot is most likely to find it (BOOM) The guns are also monitored often through their life and in fact the old barrel was de-activated precisely because doubt was cast over its continued integrity.
The uk re-enactment scene do take the safety and regulation of the firearms used in their events very seriously and my Dad also being one of the inspectors of artillery for the Sealed Knot has to take it even more seriously.
But thank you (in all sincerity) for the concern.