[Jtenkink]

I'm looking for a little bit of wisdom from some of you guys that know a lot more about this stuff than I do.

I've got a Sako A7 in 270WSM that I bought new last year. When it was new I noticed that every so often it would be a little stiff to chamber a round and get the bolt all the way closed and once it was difficult to get a cartridge removed after I fired it. That particular one I actually had to pull really hard to get it out but it only happened once so I figured it was either the brand of ammo or just a fluke. I've got probably 100 rounds through it now and the bolt is pretty consistantly stiff to close and open(compared to my old Savage 30-06). I've always just chalked it up to something like close tolerances or something like that but today I saw that some of my brass have small circle impressions on them where the "Fed 270 WSM" is stamped around the outside of the primer pocket. Forgive my lack of terminology here, I've been shooting for almost 10 years now but my brain is not coming up with the name for that part of the brass right now. Anyway, the impressions are bulges that match the small hole in the bolt face where the ejector (I think) sits and I would swear that it looks like an over pressure issue or something like that but these are Federal Premium Factory loads. Not every brass has it but I found 3 or 4 out of a box of 20 that I looked at that had pretty definite circle bulges. I'll see if I can get a picture to load so you can see what I mean.
So I'm thinking maybe the stiff bolt and these are related, maybe someone has a good idea as to how I can figure out what is going on with this gun or if its the ammo or if its anything I need to worry about. Thanks in advance!

(you can see the circles in the three cartridges at in the top left of the picture)