I have tried a whack of loads for this caliber - my gun liked 200 accubonds @ 2.88 col with both rl17 and 4007ssc - went up to 67 gr before press signs, both powders settled in around 64.8 - 65.5 grns, and depending on load they ran around 2940(min) -3050fts(hot). . It didnt like 4350 or rl19. I use regular win primers and win brass... both rl17 and 4007ssc grouped an inch or under at 200 once I found the sweet spot...the winner for my gun was 4007ssc by a small margin.
Key to my gun getting good groups was to fire 3 them let it cool right down... if I didnt do this, the shots would climb dramatically despite the bedding and such - i'm guessing too thin (and fluted) of a barrel.... barrel is 0.520 at the tip, or 13mm, bullet is 8mm, meaning there is a barrel wall thickness of only 2.5mm!
On another note my accuracy went real bad this past month - checked everything, tried tweaking loads again, then finally went to change scopes and then found the front screw on the front weaver base was sheared off and the rear one was oval shaped...... fixed that and back came the 200yd 1 inch groups!