Pressure signs.

[Unkl Chuck]

A very educational thread, a 'should read' for reloaders.
I've been loading for many years, my Speer #8 is on a shelf somewhere. A habit I would recommend for all reloaders and handloaders is a log book for loads with range notes from firing. Paying attention to standard safety protocols such as only 1 powder available at a time. Same with primers and projectiles as well. When finished with a specific load, complete the loading, box and label before moving to the next. Yes, you'll need more boxes sometimes, but you'll probably miss mkl's thriller in post #26.
Every little change can affect pressure, start working with an interior ballistics program like GRT to see how much a small change can make.
Pressure signs can vary in different firearms, I do a lot of Contender shooting and the Contender is 'notorious' for things like cratering and flattened primers particularly when fire-forming brass. Pay attention, keep notes, and learn your firearm.
Always start at a safe load and work up slowly.

 

[RC20]

My take is I look at all of the indicators and consider the gun (modern or military surplus) as well as the average of where I am at powder wise as to on the high end or medium area.

Primers can be misleading, but if you know your gun and suddenly you see Primer reflections as it were, pay attention.

 

[44 AMP]

Primers can be misleading,....

I think that could be better stated. No primer out there is trying to deceive anyone, about anything.

where people have been mislead is by other people, telling them what primer signs "mean", and particularly when linking them to certain pressure levels.

Where people mislead themselves (and others who listen to them and believe them) is making assumptions that a given "pressure sign" on a primer means a given pressure has created it, and while this is SOMETIMES the case, sometimes, its not.

Differences in the guns, the loads and the primers themselves mean there are no hard and fast rules, save one.

And that one is, when a primer shows something different from usual, SOMETHING has changed. That's all it tells you, and any "automatic" assumption expanding on that as to what, and why is speculation.

Maybe you got a cratered primer, because you increased the pressure of the load, or maybe you've got too large a firing pin hole, or maybe too long a firing pin, or maybe one lot of primers has a softer cup than the previous batch, or maybe some thing else....
Maybe its a problem, or maybe its not...

The Primer won't tell you.

All the primer can tell you is that something is different. Its up to you to determine what, and how much.