I have two Barnes loading manuals and neither give any data for Magpro and any of their 300WSM bullets, but if you go to the Accurate Powder web site you will find loading data for three different weight bullets using Mapgro. I would look at the 165 Sierra data and use this as a guide to load the 168 gr TTSX. Start Low and work up! Accurate Powders
I have had very good success with RL-19, N550, IMR-7828, and RL-17 in my 300WSM. Two favorite loads are 168TTSX and 62.5 grains of N550, 168TTSX and 64.5 grains of RL-17. Both loads are a medium load with velocity around 3000/ft sec.