[wncchester]

Mike, I wonder how you are setting up the sizer. It needs to be down far enough to make shell holder contact while under the full pressure of resizing, not dry, with no case in the die. Failure to size down far enough is the most common cause of what you are experiencing.

No matter if a bottle neck case is rimmed, rimless or belted, a loader should to size his cases so they fit his chamber at the neck. Making ammo that actually fits our own rifles is one of the advantages of being a handloader!

Try pushing a case into your size die adjusted as you normally do. Raise the ram/case fully up take a look under the die mouth to see if there's any gap between the die and shell holder. If so, screw the die down enough to close it. IF that fixes your chambering problem you may want to back the die back out just far enough to allow cases to chamber easily and no further.

If you take a look at Larry Willis/Innovative Technologie's nice collet belted case resizer you will see that it won't do a thing about hard contact at the shoulder, it only affects the case body near the belt.