There are certainly many nuance to calculating real world bolt thrust compared to the simplified calculation, but most of those nuances are second order at best, pressure times area is the first order factor.
When you look at the quick and dirty calculation (max chamber pressure times case-head or chamber area) for bolt thrust you end up with 450 BM being very similar to 556. I suspect this was a driving reason Bushmaster/Hornady set the SAAMI MAP to 38,500 psi when they created the new cartridge. This is much lower than its progenitor 450 Professional. I also suspect this is why the 30 RAR uses an AR-10 size bolt and barrel extension with its MAP of 55,000 psi. Now if you go and run your 450 BM up to 45,000 or 50,000 psi suddenly your putting loads on the bolt that are comparable to or greater than the thrust of 556 proof loads (125% or 62,366psi) put on that bolt. The lugs are at best equal to 556 lugs in strength and very likely weaker due to the larger case-head recess cut into the bolt.
It seems prudent to watch how much you over pressure 450 BM in an AR. In a bolt gun with a action that is designed to take bolt thrusts from other high pressure large case head cartridge I would think running 450 BM up to 50,000+ psi would be no problem. In an AR though the bolt is the weak link and must be considered.
I love the discussion; push, pull, and discuss this with me all you want, I don't mind. And yes my more conservative Barnes 275gr @1923fps are going to be joy to hunt deer with this year.