Loads for a 300 short mag suppressed

[WRO]

I am getting ready to build a short barrel 300 WSM, I'd like to shoot 208's and will be sizing the mag appropriately. My concern comes from an acquaintance that had a suppressor explore because it loaded up with unburnt powder. (20" 300 PRC). That being said, what should I be targeting for a starting load with a 20" pipe?