What did your mate do to his Tikka to load long range projectiles. Have heard you need to fit a new bolt stop and magazine due to the lack of room in the standard mag to fit long range projectiles.
Just finished posting Yogi then saw your comment to camo wsm, hope this helps?
C.O.A.L = 2.885 with the 168 Amax & 165 Interbonds, this fits a standard mag with about a 20 thou or half a mm jump.