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?

This helped explain it:

I use Sportsmatch on a Tikka and they fit like a glove.

Yep.... and tough as hell. I’ve accidentally “drop tested” mine a couple times... and they’ve always held zero.

Get some!

If any slop just push it to the forward till it stops. Just like any other recoil stop. The rear doesn't mean jack squat. Scope goes forward with recoil

The Sportsmatch rings for the Tikka T3x are out of stock everywhere I look. Must be good rings.