now i understand. By changing the case you got more internal volume. How do primer pocket loosen up with those Win cases ? I'm not used to those case.
He did not change the dimensions of the case, he uses a faster powder so uses less to achieve desired velocity, hence more room in the case.
Guessing if Varget was used he would not be able to get enough in there to make up for the lost velocity of the slippery bullet.




















































