The latest version of the Barnes Reloading Manual does not have data for the Tipped TSX in the .257 Wby mag, but does have info for the standard TSX bullet. I am quite sure you will be safe using that data for the Tipped bullet. I have done this several times now with the new Tipped bullets and have found the loading data for the regular TSX to be quite safe.
For the .257 Wby Mag using the 100 grain TSX and IMR 7828SSC powder Barnes suggests a minimum load of 66 grains for 3314 fps and a maximum load of 71 grains for 3521 fps.
Even though Barnes tested the IMR 7828SSC powder, this data will work just fine with regular IMR 7828 powder.