I don't have any Tikka's in 6.5x55 but my Dad and I both have Sako 75's in 6.5x55. They both shoot really well. We both use Lapua brass and CCI BR-2's. With 139gr Scenars and N560 they will both shoot five shot groups under 0.3 inch @ 100 yrds. I have one five shot group from my rifle that's under 0.2 inches. Not bad for a walnut stocked hunting rifle w/ a 10x scope! For a hunting load we both shoot 130gr Swift Scirocco's w/ N560. Both guns will run under a half of an inch with that combo and it works great on game!
