Fluid steel or damascus can fail- the only accident I have seen was a 20 O/U that burt at the chamber of the top barrel- that was fluid steel.
My point is have a qualified person check wall thickness and shoot low pressure. That is all that is required by US standards on US guns. But the back yard method can cause damage and proves little.
I have run across far to many English and european guns that "someone" has opens the chambers to 70mm etc... I don't want to own such a piece much less shoot it. I know of one dealer selling a BP proof Grant and telling prespective buyers it is fine to shoot with modern ammo.
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