Reading pressure signs from cases and primers is somewhat of the black arts. If you load long enough you get a feel for high pressure. I personally feel if the bolt handle starts binding you are probably too hot. One of my tests using a bolt action is to point the muzzle straight up after firing and unlock the bolt. Without pulling back even the slightest amount I release the bolt handle and see if the bolt will extract the case fall from it's own weight.
Yes, I know there are variables even with this to include chamber dry or lubed, FL sized cases or neck only, etc. But my reasoning is:
The force to extract is pretty consistent compared to my subjective "feel".
If the case is binding enough to resist the bolt's weight then I should check things out.
If I am hunting I want the gun to work no matter what, etc.
I do not measure case head expansion because of the great variation of brass hardness between makers and, in some instances, differing lots from the same maker. That being said, too much head expansion across the web is bad ju ju. If I find it I back the load down.
I have always read primers because they have been the first thing to let go. A system fails at the weakest link and overloads have always hammered the primer first for me.
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In the photo above are two Federal #215 primers that are known to have hard and thick cups. If the #215 is showing pressure you got issues. The left is an unfired primer seated in a 375 Ruger case. Two things to notice:
1) The radius at the perimeter of the primer is pronounced. That is, it is a larger radius than the other fired primer.
2) you can make out the seating punch indent in the surface. Primer surface condition can tell you a lot, including how rough the machining is on the bolt face. These primers measure 0.210" to the nearest 0.0005".
The right primer is from a 300 WinMag load of 150gr TTSX/ 79gr RL 19/ Fed #215/ 3.500" COAL. Velocity = 3349fps, SD= 9fps.
If you click on the photo and look at the radius of the outer edge of the primer it has sharpened up a lot. The slight cratering is from a light firing pin spring because every load in this Rem 700 craters to that amount, even the light development loads. Note the imprint of the bolt face on the primer surface. This gun has a rough bolt face and it makes reading the primer easier because the imprint sharpens up very progressively with increasing pressure. The tool marks are very well defined.
Back to the primer edge radius. If your head space is pretty tight this only occurs with high pressure. It is progressive. When punched out carefully the primers show a mushroom shape with the diameter at the radius measuring 0.212". 0.002" increase is the max I will allow with the #215. But if the radius forms a sharp 90 degree edge I take that as a touch too much. Usually at that point the bolt will not extract freely when the muzzle is pointed straight up.
This rifle is equipped with a PT II strain gauge and that load tests to 62Kpsi. The primer appearance is consistent with the "feel" I have developed over a 40+ year reloading career.
Just my two cents and a picture.
KB