Is your Tikka at least a 1:8" twist? If it is 1:9 or slower, you probably should focus on 69 grain or lighter bullets. If it is 1:8 or faster, then you've got lots more to try with the 77tmk.
First, get 100 rounds down the tub before you judge anything about loads.
Second, I'll assume your cases are all the same lot and brand, uniformly annealed, sized, trimmed, and chamferred. You may be able to mix them up later and still have accuracy acceptable to you, but eliminate that variable until you have a known good load.
Third, not to slight Varget, but it is not a universally best powder. Try N140, which has almost exactly the same burn rate but smaller kernels, so it is easier to trickle to the tenth grain or less in such small charge weights.
In my gun, 77tmk generally shoots better with some speed (relative to the chosen powder's burn raye). But, my loads become really compressed trying to cram anything near max loads of Varget in a .223 case at a mag-length COL. N140 is only slightly better. With both powders my seating stem would badly deform 77tmks until I made a custom stem mated to the full 77tmk ogive (,except plastic tip).
I can get similar speed with less compression and deformation using a faster powder. I haven't finished working up 8208xbr, but it looks like I may be able to get better accuracy from it at ~50 fps below Varget and N140 loads. You can also look in reloading guides for any options with faster burn (lower fps) single-base powders like H322, H4895 or IMR4895, N135, etc. Hodgdon's data center will point you in the right direction, the Sierra guide has a number of options, and check VV's guide, as well.
Of course, you can get higher velocity from published loads of ball powders and double-base powders like CFE 223, AR Comp, and anything (of the right speed) from Ramshot or Alliant. But I prefer temp stability versus higher velocities.
Good luck!
