Originally Posted by pocketchange
Measure just above the case head recess (in the same location every time.. mark with a sharpie),
if you notice ANY growth in the diameter,
you are over pressure. As in .0001 plus.
This is the most pressure resistant area of a cartridge and if it starts to increase.. BEWARE.
Good advice from pocketchange.
Either the area just above the base is expanding, or your case is too long (shoulder needs to be pushed back.)
Is the bolt stiff to close on an unfired round?
You can take a magic marker and color the entire case then carefully chamber then eject it. You will probably see scuff marks at the pressure point. I suspect it will be at the case web junction in the base.
I doubt you have damaged your rifle, but you need to back off things and get this problem solved. Cases that are hard to extract can scratch your chamber, cause excessive wear, even galling of the locking lugs, or can break an extractor.