Unless you're shooting the test rifle used to develop the load data, you wont get the same results. Your rifle could very well be producing lower pressure than the test rifle for any number of reasons. Thinner brass, larger chamber, more generous throat, different lot of powder, and countless other factors. If you're looking for a certain velocity and it's in the book, and you have a rifle that is a known strong design and is in good condition, I'd keep going (in small increments) until you run into something; either you reach the published velocity for that barrel length/bullet/powder or you get some issues with pressure.
Also remember that most pressure signs aren't a sign of a specific pressure universally. Federal brass can develop loose primer pockets and show ejector marks at safe pressures for many cartridges (happens with normal .308 loads easily). Other harder brass may not show signs until the pressure is dangerously high. I have a .308 with a fairly tight chamber that will have sticky extractions below the max published load. Every rifle is different.
Primers are next to useless for any sort of pressure sign unless you are familiar with that brand of primer and how it specifically reacts to different pressures. Federal primers will start to flatten with upper .30-30 loads (42k psi) and totally flatten with safe .308 loads (60k psi). CCI primers will just start to flatten in a .300WM (62k psi) and wont totally flatten until you're into suicidal pressures.
A cratered primer can be caused at low pressure by an oversized firing pin hole in the bolt face.
