I have to take exception to the statement that primer appearances are of no value. Without having a pressure barrel or piezoelectric or stress tester, a loader has to use every indicator of pressure available. Relying on only one could lead to disaster. Its become very popular to dismiss primer appearances, but they are very useful if approached as a comparator to many other signs of normal pressures. Comparing gun to gun or factory load to hand load can reveal a lot. Things like sticking cases or hard extraction may well mean you're in the land of no return or KB land. Some cases like Ruger 375 or WSM cases are so stout that it takes a lot to expand or stick them. Or soft case heads expand a lot while strong cases like the two mentioned take an awful lot to expand.
Using primer appearance requires you compare low pressure loads to increasing pressure loads. Flattened primers usually mean you're getting to the upper levels of practical pressures, but deep primer pockets , or long headspace can produce them too. If lower pressure loads produce nice rounded primers and they eventually become flattened, you can safely surmise that pressures have increased. If they are completely flattened and totally fill the pocket to the edges, its time to evaluate.
Cratered primers tell you that pressure or design limits are in sight. But they can also indicate oversized firing pin holes or weak firing pin springs. All these factors are useful in establishing practical working pressures.
The decrease in recorded velocity as load limits are approached seems to be a common phenominum. This says you are in never never land and anything, any variant can cause a real pressure excursion. Your gun is trying to warn you! Just remember to use all the indicators available for a complete picture.
I could prattle on much further, but Ive probably made enough people agitated already.
Last edited by rogn; 03/08/14.
