No need to do a chamber cast to see if the neck of the chamber (or the combo of brass and chamber neck) might be too tight. Instead try to insert a bullet into the necks of fired cases. If the bullets won't slide in easily, then the necks are too tight for that chamber.
OR the neck of the chamber is a little shorter than standard. This results in the front end of the neck being lightly crimped around the bullet. If that's the case, trim the brass a little shorter.
