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

[DeNinny]

It is 100% impossible for that flap to be present while in-battery, even in a sloppy, out-of-spec chamber. Again, if you had a case failure in battery, where do the back-end gases go?

That flap occurred within the unsupported area. Within the feed cone itself. And it 100% has the room for it, according to my measurements. The feed cone is wide open space for it. And while in battery, it looks like the other half of the flap bent right into the bolt itself and right over the extractor.

At those pressure levels, they will destroy the extractor, usually split the carrier, bow-out the upper, bow-out the lower, send fragments from the carrier and bolt in different directions, with magazine blow-out being the least of your worries.

Sorry, but the pressure quickly dissipated as the bullet got farther away from the case mouth. And it dissipated at the blowout. As soon as the blowout started, all the pressure started releasing.

And as OP stated, the pressure at that end ended up blowing out his magazine.

I'm very sorry but the more we discuss this, the more likely I see the blowout model occurring instead of the extraction model.