RE: Pressure Signs
Two common signs are the flatness of the fired primers and growth of the case diameter just ahead of the extractor cut. The case can be measured with a precise blade micrometer and even .0005 growth is too much...back off!!!
Re: primer flatness:..look for loss of the radius in the corner of the primer. A newly installed primer had a generous radiun in the edge where it is in contact with the primer pocket.....if the pressure is high that radius disappears making the primer look very flat.
Another sign is a chronograph reading.....if you are shooting faster than factory loads you might want to rethink your load. Most factory loads are near maxed out and it can be unwise trying to improve on some of them unless you know that the factory loads are tamed......such as the 7MM Mauser and other cartridges.
After all this you still could be over max and not know it but these things will go a long way towards safe load development.
Read your loading manual carefully...some loads are specific for a particular gun and not to be used in other guns.....
This applies only to modern boltaction guns where the cartridge case is the weak link....It absolutely don't apply to leveraction guns such as the M94 winchester and Marlin 336 and a lot of other guns