Hi Solrus,
I had my action bedded with Devcon (Aluminum) paste.
Fitted a Timney trigger and that was about it as far as customising went on that rifle.
Here is the load I created that would give me one hole groups with ammunition that fed through the standard magazine.
102 grains of RE25, C.O.a.L.3.710" base to bullet tip.
This load pushed a 30cal. Berger 210 grain VLD at 3250 fps, with a 7fps E.S.
I have since sold my 30-378 and am building a 300 RUM as its replacement.
Good luck and hope the load works as well for you as it did for me.
Cheer
RR