I work up until there is a change anywhere around the extractor groove diameter as measured with dial calipers. Then I back off 4% powder charge for temp stable powders, 6% for regular powders for my hunting load.
Vernon Speer suggested 6% in 1956, but he did not have temp compensated powders.
I have done this with 223, 243, 250 savage, 257 Roberts, 25-06, 260, 6.5-06, 280AI, 7mmRM, 308, 30-06, 300WM, 8x57mm, 338WM, and others.
This does not work in 6mmBR as the primer pocket is not the weak link. The primer pocket is too strong. The primer is the weak link. The best I can do is CCI 450 small magnum rifle primers. To get them to go higher, some guys have GreTan bush the firing pin, and some more performance can be had.
The good case heads:
A) 6mmBR and 30-30
B) 223
C) Belted magnum
D) Mauser case head large Boxer primer pocket.
The bad case heads:
X) 30 carbine
Y) 10 mm
Z ) 25acp
There was a guy on AR, A**CLOWN, 15 years ago that could calculate Von Mises stresses in a case head.
His threshold of case head yield pressure predictions matched my emperical threshold data fed into Quickload pressure predictions
https://en.wikipedia.org/wiki/Von_Mises_yield_criterion
