From my experience, yes, a 338 offers more than the 300.
After seeing and witnessing elk killed with 243 to 375, being in Africa last year with 5 other guys with a 300 H&H, 330 Dakota, two 338's, two 375's and 30 some animals taken from steenbok to eland.
My subjective opinion is that bigger diameter bullets hit harder. All the other calibers worked just fine, but for visible impact, the bigger calibers have it. That line starts at 338 and bigger in my opinion. YMMV
For me this is the very grey area of performance. The 30-338 factor. I agree with the Weatherby philosophy of that shock oomph factor. For me it stops at the 30vs338 level. The punishment on the shoulder vs the crumpled game is up in the air. Once its kicked up to 375 levels I no longer go with the Weatherby philosophy of speed,hydrostatic shock etc... Guys, this is just me and my limited expierences. I've seen the 340 Weatherby absolutely crush game. Same as the 338 win. No difference except in the shoulder. I will say that I truly believe that the 300 Weatherby or for that matter the RUM are far superior to the 300 win and offer more than the 338 family.
