Just a check with 4 reloading manuals. The 340 is 187 fps faster, and with a 250 grain bullet that is a game changer
I can also add, l have owned 4 different 338 win mag, in Winchester, Sako, Ruger, and TC barrel. None would push a 225 grain much over 2700 fps much less a 250 grain
I did try a 270 grain ELD-X in 340, that was going 2700, but wouldn’t group well