Just to get clarity here, you have sized the case and it won't chamber, is this because the case mouth is catching on the edge of the chamber and you can't push the case into the chamber, or you have sized the case, it goes into the chamber but you either have a very stiff bolt closure or unable to push the bolt handle down?

If it the former, it isn't a sizing issue, more likely the feed ramp.

If you can get a case in the chamber but can't drop the bolt handle it is a sizing issue.