Referring back to BR's pic of the blown rifle.  That 30/40 case held.  The problem was how much it had to hold, as evidenced by the expanded primer pocket.  Yes, it was likely a little weaker with it's machined extractor groove, but it was strong enough to hold through all that primer pocket enlargement.  Someone didn't load it right, or created an SEE event shooting a thick jacketed bullet in a rough throat with a light charge.   My opinion anyway.