My three best shooting loads in a 20" 54cal and 300gr+ bullets all shoot best with 110gr to 120gr. The 2 best with 120gr. I really didnt want to try more. I dont know if it was burning it all but the groups did tighten up from 110-120gr on the 2 best loads.

In my 45s and 50s and longer barrels they usually topped out at 110gr or an occasional 115gr. I haven't tried BH209 in my Savage yet so that might change with a heavier bullet.

Ive also used almost nothing but Win209s and even shot some great groups with WinT7s with heavy loads. Im not so sure a mag primer is always needed depending on your breach plug and primer fit.