my vote is for the 7MM STW. Remington is the easiest brass to get at the moment and it has worked for me so far. Winchester is probably better but is hard to impossible to get. I am still looking for the right load for my gun but will have that narrowed down soon. I have a friend with the 300 RUM and either will do the job for you. It is all about being confident in the gun. I got the 7MM STW because it was different.
Founding member of the 7MM STW Club
Member Texas Cull Hunters Association