measuring case rim diameter...high pressure sign?

[lpreddick]

i saw this mentioned in recent issue of Varmint Hunter's mag. my impression is that high pressure produces enough bolt thrust to flatten the case head actually enlarging the diameter of the rim. i cull cases when primer pocket gets loose, so i measured them and the rims were indeed .002 more in diameter than new. is this worth following and does it happen early or late ?

 

[TonyR]

I have never measured the rims but the expansion of the bottom of the extractor groove on the first firing seems to be one way to detect excess pressure. I use a blade micrometer because you need the 0.0001 inch level of precision to use this method.