So, I haven't found a diagram, but the Tikka manual states:
"Scope mounts will fasten to the 17mm rail on the top of the receiver. A circular hole on the front of the rail will act as a recoilstop, ensuring a positive lock between the scopemount base and the receiver."
There is a small circular hole and a bigger round, but it looks ovalish to me....
The sportsmatch rings have a steel recoil pin that is too small for one hole and too big for the other.... So, what's everyone doing?