I doubt it was the brass.
MM
Unless it was a range pickup of commercial federal brass, i.e. what you find in American Eagle ammo. That stuff is way to soft, so I could see that being the root cause.
By no means am I the senior hand loader here. But the only brass I’ve had issues with has been Federal; .270 Win and 7mm RM. Some of each, once fired, had primer pockets that wouldn’t hold a primer. On the other hand I’ve loaded Federal 9mm and .40 with no issues. But it’s be hard to get me too go with Federal on rifle ammo again.
Soft brass, such as to allow primer pockets to expand is sure as hell not going to cause a failure like that.
That is high pressure & the brass would have had to have had numerous firings on it to have weakened to that level.
If an AR bolt is even a little out of battery, the FP cannot reach the primer, so I really doubt that the gun fired out of battery either.
Too much powder is far & away the most likely culprit, but as in most post mortems like this, we'll never really know, so pick your theory & stick to it.
MM
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