I had a partial case head separation using a 1.8oz buffer

[DeNinny]

At those pressure levels, far more damage would have happened.

I disagree because it could have easily dissipated. Remember that the pressure was also dissipating at the bullet end. And again, as soon as the blowout started. Pressure is going to drop like a rock.

There had to be some pressure relieved, but enough residual pressure to allow gas escaping from the case to participate in the partial case head separation and flow around the bolt.

Or, there was enough pressure to blow the case wall. And it started relieving there and also through it's normal path. With two escape routes, the mouth and the blowout, the pressure dissipated VERY quickly.

Earlier case failure isn’t supported by the way everything is presenting, the intact extractor being the biggest piece of evidence.

Earlier case failures (2) are supporting the failure model because their deformation shape and location of score line are indicative of the unsupported head area expanding to match that of the feed cone shape (to a degree). Unfortunately the third failure, the blowout one, expanded even further, to the point of blowing out.

Again, all the pictures are supporting this. To a "T". And the intact extractor is irrelevant here. It played no role in the model I'm explaining. And with the two cases NOT blowing out, of course it would stay intact!

If you have seen in-battery/over-pressure catastrophic failures, you would see the distinction.

I have seen them. This failure is just one that happened at a lower pressure than those others.