Tom,
Believe it or not, I'm getting those groups with the first load that I ever tried in this gun. It's so simple, I'm almost embarrased to list it. But, here goes:
Hornady VMAX 55 grain
H380 - 38.0 grains
CCI magnum rifle primers
As to seating depth, I tried all that stuff about backing off from the lands in little increments, and the groups all opened up. My best groups occur when the bullets are seated so that they just barely fit into the magazine. These bullets have a considerable jump to the rifling.
All this with unsorted brass. Just trimmed per spec, flash hole uniformed, and primer pocket cleaned out. BTW, I'm neck sizing, too, but I don't know if that really matters or not.
I shot 10 groups (of 3) two weeks ago and averaged under 0.40". The best group was 0.18". Yeah, I know varmit guns should be shot with 5 shot groups, but, hey, it's my gun!
I hope you have the success that I have had with my Tikka. Before now, I've never shot any varmit calibers. Sure makes those big centerfires seem like bullies to my shoulder! Good luck. Please let me know how this recipe works for you.
The Blade