It will work fine, but likely be too short to load heavy bullets at the optimum length (if you’re reloading).
Tikka limit the length by the back of the magazine being thicker/thinner depending on caliber (bolt stops then set to this, easy to file to pick up on a longer magazine).
If you’re reloading, you’ll want the longest available, I’m using the Mountain Tactical LA magazines for my 7PRC which are about as long as you can get whilst staying standard T3 style.
300Win Mag is what you want the magazine to cater for.