Partitions create high pressures in my experience. I tend to be more cautious with them. The big thing to me is being jammed though. Not surprised you had issues at only 1 grain over. Book max is certainly not for jamming a load. I am surprised you had no signs. Bolt was easy, no ejector marks, no flat primer? Good reminder for all of us.
I think adding chrono data to your situation may have helped to prevent.
