....The discussion as to the primer (viz. the primer bulge happening as the headspace failed) seems fair. But, it does not account for the extractor imprint. Logic tells me that, if there was to be an imprint from the extractor (as there is), then it would have to have happened before headspace failed and before the chamber wall blew out. First, the extractor is not in the region that failed. Second, on the chamber wall blowing out the pressure (necessary to force the shell head into the extractor to cause the imprint) would drop off rapidly.
I think this was a hot reload that met up with a chamber with a very weak spot.
I would consider a couple of things. First, I dont think a slight extractor imprint in the brass is more significant than the blown out brass on the opposite side, the shell looks to have distorted as the shape of the chamber was changing. And second, I do not believe the primer of the blown shell is flattened, to me meaning that at the point the shell was fired it was not over pressure or if over, not significantly.
Its a mess, but I dont see a flattened primer cup or other signs like flattened manufacturer stamping on the head of the shell. Apparently, the load fired out of the barrel and there doesnt appear to have excessive thrust against the breech. It appears to have failed radially, and the extractor happened to be opposite the force that it took to peel the shell open. Only thoughts.
