Dan: I should have linked the summary, without the extraneous verbiage, starting about 1/2 way down here
https://docs.google.com/document/d/1ZnptAPvQIlWG5n5UU2FmKcFpYtVmOSc4b7K7G9IBs4g/edit

My opinion was that the barrel failed because of the critical juncture of 3 factors:
An over-pressure (re)load.
A defective braze of the top rib extension wedge to barrel.
Inclusions (possibly a large inclusion) in the barrel wall.

The barrel did not fail because of low cycle metal fatigue.

A 2 3/4" shell in a 2 9/16" chamber may have been a contributing factor.