I knew about bullet push back, but thats not what happened, i checked the rounds, I swear.
As for the ring around the case head?
Well, the all seem like that, its mostly because reloading dies for 9mm cant really resize that very bottom part of the case. I am not aware of a die that does to be honest.
I cant verify every single round of 9mm i turn out has 5 grns of 231, I check every ~10-15 rounds or so with the scale, but i dont weigh every powder charge.
I will pull a few and look.