According to the drawings of your print the max length of your chamber is 2.025". If you are trimming to the stated 2.025" stated in the thread then your brass has no place to flow, thus causing your problem and the Nosler/Norma will only make this worse since it's so soft. Have you measured the chamber? What is the length of your fired brass? I always trim .007" shorter than my chamber measures to allow for growth. I think the older longer throated reamer was @ 2.045" if I'm not mistaken. Just my .02 and worth looking into and would be interested in your findings.
Sully
Sully