I have a CZ 550 in 6.5 X 55 and use Hornady 129 grain Interlock with 45 grains of H4350, very accurate very effective, I also use H4350 for Hornady 140 grainers I can't remember how much off hand, but also very accurate. For the 140 grains I would start somewhere around the 41/42 grains of powder mark if I were you. With regard to the 129 grainers this load is safe in my rifle as always, work up a safe load in your own rifle.
Hope this helps
John