Observing the wound, I assume the puncture was done by a fragment and not gas. No burns can be seen.
From the picture, the wall thickness appears sufficient. The crimp probably opened correctly but when the barrels failed, the gasses went multi-directional, thus blowing the crimp backwards and melting it somewhat. If the powder charge was doubled, odds are that the case would have ruptured and burst closer to the head. My picture estimate would be metal failure. It must be remembered that barrel bursts can be caused by a conglomeration of problems. Too hot a primer, slightly more powder, loose base wad, heavier shot weight, etc.
I don't see a bulge that indicates a bore obstruction.
Just some thoughts.
I agree with the metal fatigue, and also commend the sharp set of eyes that noted the imprint of the Damascus pattern onto the exterior of the green plastic shell casing- I also concur with the oxidation pattern analysis presented- very true, more so with the amalgam of iron and mild steel used to make such tubes- it must also be remembered that the iron "skelp" admixture could consist of melted down horseshoes, nails, etc-- I am not a metallurgist, but when we worked for Townsend & Bottom on the West Olive (MI) plant years ago, for all those welders, myself included, who passed their coupon testing the first time, the company gave us a paid membership in the AWS- and I read and kept all my issues, and there is where I became interested in metallurgy, mainly ferrous such as we looking at here. How did the top and bottom ribs fare from this incident?? RWTF
