RE: 300.wsm vs. 300 rem ultra mag.
Ruddy, what do you think happens with a 270 and you add 10 gr of case capaicity to it? You get 100-200fps gain. Ok, stay with me. What would happen if you expanded the 308win case to hold 15 more grains of powder and actually added it. You would have WSM that gets about 200fps more velocity.
Ok, I know its difficult to wrap your hands around, but for any case you have to add more powder to get more velocity and stay under safe pressure limits. Understand? If you don't, I can help you more later.