Don't go over 180 gr with your 300wsm, you will loose to much velocity and energy. The cartridge does not have the guts to push it fast.
180 gr seem to be the sweet spot for the 300 wsm. TSX, Partition, or A frame will drop it like a rock.
As the TSX carry huge energy through the game you can get away with a slightly lighter round such as the 168 or 165 gr.
I ran 165 gr TSX in my 300 WM last year and they were very devastating!
Good luck!