Something doesn't sound right about that, I'd be concerned too.

First thing I'd do is see where the case is contacting the chamber with the dies set for 2k bump. Smoke a case (or I use a black majic marker) from the shoulder to the neck and chamber it several times. I usually just draw 4 lines all the way from the extractor groove to the neck so I can se where I'm getting contact on the case body also. This should tell you where the "tight" spot is on the case - where the marking or smoke is disturbed.

It may be that with the thinner turned necks, the base of the neck that's not geting sized by the bushing gets expanded more upon firing and is causing the contact. If that's the case, when you set the shoulder back 7k it may create enough length clearance from the chamber to allow you to feel loose bolt throw. If the base of the case neck is contacting the chamber, I wouldn't worry about that - it should center up the cartridge nicely center bore every time, but may cause problems if you ever get significant carbon accumulation there (Carbon ring). If you feel the need eliminate contact there, you'll need to use standard type FL sizing die rather than bushing type.

Also, to cover all bases, check to see if you have any crud on the bolt face and that the ejector plunger moves freely down to below surface of the bolt face.....

You might get more responses if this goes into the reloading section...
ELkbane