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.
