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

[Zeneffect]

Yes, where the feed cone transitions to the supportive chamber walls is the area I'm thinking of. Rather than a hard angle, it should have a radius. If failure occurred there in battery, there should be evidence of the transitional radius on the upper half of the brass that was supported. The top half should have a slight flare to it where it failed, not a straight shear.