Same as military Lake City except that since it is new brass, not once fired mil brass, there is no primer crimp to remove.

You said that you were using BL-C2 powder, what was the outside temp? Had your rounds been sitting in the sun? The reason that I ask is that BL-C2 is known for being very temperature sensitive and doing almost exactly as you described when it gets warm.

Nothing that you described would be caused by the brass being range pickup or even cheap brass. You are describing signs of gross overpressure, not brass failure.