Are you full length resizing. If you are, it is theoretically possible that your case is being shoved towards the ejection side of your chamber by the springloaded ejection plug causing the bullet to touch the right lands first??? Not sure if this makes sense, just brainstorming here ;). As Tyler said, you are still getting groups that arnt too bad here. I'm no gunsmith, but as I think about it, I don't think it is possible for the rifleing to be cut at different lengths. They are cut by a rotary tool and there would have to be some absolutely horrible things going on to get ther rifling cut to different lenghts. If you are fl sizing and you do have a spring loaded ejector, I would consider doing PFL resizing or neck sizing. Just another thought.
I used to re-load but now I "hand-load".
-- Well, at least I try