You HAD to ask that! But of course, it is a good question. And perhaps the most difficult question to get a definitive answer for.

Flattened primers CAN BE a sign of excessive pressures, but often aren't. Some usuallyreliable signs, however, consist of primer pockets that become noticeably LOOSE after the first shot, to where it is "too easy" to seat new primers; a boltthat is difficult to open after the shot; marks on the cartridge head from the bolt face, such as ejector hole or slot impressions on the brass, etc. Any of these indicate that a 5% reduction (at least) in the powder charge is needed. If a primer actually FALLS OUT (like happened with Ridge Runner's 6.5 Gibbs!) of the primer pocket when you open the bolt, cut that charge at least 10%!