To bring this back to the question, I spent a couple of years attempting to build a long range rig with a Tikka with mixed results.

Mine was in 7 Mag and limited by the smaller OEM magazine size, shorter bbl and slower twist rate to throw the really heavy bullets that excel as long range shooters. It will shoot 140gr PTs in a .70MOA group on its worst day but is very erratic with anything heavier. My T3 was at the very end of the run prior to the T3x and was part of a group buy with co workers and those of us who got magnums have all found the same issues so it may have been a quality thing with that batch.

If I were to do another long range rig with a Tikka, I would definitely go the chassis route and see if I could find a longer GRS bbl on sale somewhere. People I have known to go that route are extremely pleased. For myself, I kind of got over the long range thing altogether.