Sounds like your primer may be too high.
First lay a straight edge across the case head and see if there is any space between the top of the primer and the case head itself. The primer should be seated a few thousands below the case head into the primer pocket.
I can think of a couple of things that could cause your issue:
1. You are not really seating the primers all the way down.
2. There is a small burr on you bolt face.
Check around the firing pin hole on you bolt and verify that there is no burr that could be scratching the primers.
If bolt is okay, and the primers are too high it is possible that your primer pocket is too shallow (you said you cleaned the pockets, so I'm assuming residue build up at the bottom is not the issue).
A primer pocket uniformer may be required. This tool will make sure your pockets are in the correct depth and diameter. I once had a bag of 100 new unprimed cases from Winchester that had 25 percent bad pockets; a QC problem at the factory. If the pockets are too shallow you need something like this:
http://www.sinclairintl.com/reloadi...clair-primer-pocket-uniformers-prod34720.aspx
Other manufactures make a similar tool but this is the only one I have ever used. I don't use the handle but just chuck the uniformer in my drill press at around 500 rpm. The uniformer corrects for both depth and diameter assuming both are on the under spec size.