Thanks for your thanks, Terry, this stuff is fascinating to me and has always been that way. You may also be interested to read the 'Finding Out For Myself' articles in The Double Gun Journal about damascus barrels and their relative strength compared to fluid steel barrels.
I totally agree with your assessment of the oversize thread practice, and hope I never become guilty of that sort of thing. IMO the smith should be able to screw the barrel completely up to the shoulder by hand or at most with the weight of the wrench, if this isn't possible then something is wrong and one set of threads or the other needs chasing.
I see no difference between the various action generic types so far as thread engagement is concerned, the primary consideration in my mind would be the thickness & heat treatment of the barrel thread shank versus the thickness & heat treatment of the receiver ring.
All barrels will swell a certain amount when fired, the amount of movement depends upon the pressure applied to the chamber walls, the thickness of the shank and the steel's heat treatment. As long as the steel's yield point is not exceeded then the shank will return to its original dimension but in the meantime during the few milliseconds of peak pressure it may have swelled enough to crack the receiver ring if the fit is too tight or the ring is too brittle. Actually IMO this occurs far more frequently as a result of added expansion (due to heat buildup from continuous firing) than from the actual firing expansion alone.
I remember a few years ago a Sako blew with a factory load and the uproar was tremendous, as you can imagine when a respected maker's product has a catastrophic failure. The failure mode was similar to the subject high wall's in that an initial failure of the barrel wall then led to overexpansion of the receiver ring and the blowup. The pressure was normal for a factory load, the receiver was found to have no flaws and to be well within factory tensile strength parameters but yet the ring was blown off. How?
Because the normally-high-tensile-strength Sako barrel was found to have a longitudinal flaw that allowed it to expand beyond the hoop strength limit of the receiver ring, even though the chamber pressure was perfectly normal. Just as the low tensile strength of the high wall barrel allowed it to expand enough to actually split and then crack the receiver ring under the high pressure of the 32-40 overload. In both cases the beginning of the failure centered on the barrel's thread shank rather than any fault in the receiver itself, and if either barrel had been strong enough to resist splitting then their respective receivers would probably have survived undamaged. That's why I consider it so important to use modern high-pressure steel for any barrels chambered for high-pressure cartridges, especially in these old single shot actions that sometimes have smaller thread shanks.
Regards, Joe
