The post I read about it said 2800 fps + with a 225 gr bullet which would be right there with the 338 WM. It uses a standard bolt face which would be a plus if you wanted a 6 lug Weatherby action or had a donor action with a standard bolt face.
The case length of the 6.5 RPM is 2.570” which is longer than a 280AI case. If the 338 is the same length and you were trying to seat bullets out to maximize powder capacity, I think you would wind up with OAL problems in a Tikka.With the RPM case, I keep trying with the idea of another Tikka barrel to go with my 30-06, 7-08, 25-06, 22br.
I haven't looked at 338__ numbers yet to see what comparisons can be made.