Sorry to burst your bubble, but measuring case head expansion is meaningless in the real world, it's about as accurate as measuring primer appearance as an indicator of pressure.
Also, it sounds like you're not measuring correctly, the expansion line is even less accurate because no case has even wall thickness all the way round it's circumference and thinner brass expands easier than thicker brass and may give false measurements depending on where you measure the case. It's a futile exercise trying to determine pressure measuring case head expansion.
Sticky extraction, ejector marks and scuffing of the case head if none of the others are present, is a sure sign of excessive pressure.
I have discovered excessive pressure closely follows these signs as it is increased, ejector marks are first, then hard bolt lift, then hard bolt lift AND sticky extraction, then all the above plus blown primers, then swollen case head and rupture, mallet required to open bolt and rifle damage in most cases. The range of pressure this occurrs in can be as little as a spread of 20, 000psi over maximum SAAMI pressure.
Plenty of folk load to 70, 000psl without knowing it because modern brass is stronger due to better alloying and smelter techniques, but once you get past this point, things go downhill quickly.
Cheers.
gun)
