Thanks xausa,
Subtle differences "discected",
My Loadbook32 lists the 300 H&H as 85.7 grains of water and the 7mm Rem Mag at 83.0 grains of water. That would be 2.7 more for the 300 H&H.
However, when you calculate volume "without the neck" (that is to the base of the bullet) for each case, the 300 H&H is 76.4 grains of water and the 7mm Rem Mag is 76.7 grains of water - actually 2 grains more than the 300 H&H. Another tiny reduction in necking down the 300 H&H from .308 to .288 results in the 300 H&H having 76.3 grains of water to the loaded base of the bullet.
When all is said and done, the 7mm Rem Mag actually has 4% more capacity because of its fatter case.
With the 280 Dubiel being listed as approx 3 grains less than the 300 H&H, I'd feel pretty comfortable using its loading data for my .280 OKH cartridge; if only I could find someone that has more data from experience loading the 280 Dubiel.
