I saw the same thing in my 700 with SRP alpha brass/gmm primers and honestly I just ran it. From what I've seen a primer flattening happens before it flows so just go by the flattening of the primer. I've measured my brass for expansion around the case head/webbing too but I think primer shape is about the easiest and first sign you see.
I'm not a guru by any means but that's my two cents.