Re: 270 WSM Norma Brass
I have considerable experience with .270 WSM cases. Both as the parent for 6.5 WSM and as native .270 WSM application. I notice little difference between Winchester and Norma brass in volume. I have bought 3 different runs of Norma and two of Winchester. I like Nosler brass best. They are Norma cases sorted for weight.
I have Norma cases that have been annealed twice and at least 20 firings.
I have had to discard cases because of loose primer pockets too. I think it is your pressures (have you calibrated your scale recently?). I am guilty of running the "ragged edge".
I like 140 gr .270 Berger and Nosler AB over MagPro with magnum primers. This combination is 80 fps faster than other powders I have tried. I have tried SuperPerformance, Retumbo, Alliant 4000MR, R-22, R-25, VV N-560, VV N-165, Ramshot Magnum, Win 780. I have not tried H-1000 or H-4831.