Woodsy you should have seen more than your share of broken bolts at the small lug.
I have a seen well known Kiwi action that was proofed for 144gn NATO that had all 3 lugs cracked from loading up 175gn projectiles just under max specs. Sorry if i am a little wary of the maths.
Oiled proof rounds increase rear thrust big time just ask the Indians about the 2A. Oiled and put away then not dried out with a proper chamber rod rag is more than likely a big factor in over pressure issues or water in the chamber.
Theory dose not always work and maths is not a perfect science. To many cases to say other wise.