Thanks @Skinner Precision, LLC for all the info and wisdom. This is a valuable thread.

Here's an article on pressure signs with some good example pics. The comments about primer 'cratering' are consistent with with what Skinner has already said: many rifles will produce cratered primers under normal pressures. The concern is when something changes (never cratered before doing X).
https://rob.primalrights.com/library...nding-pressure