The difference I see is the 7mm will hold more powder, and is capable of handling bigger bullets. Say, 160 to 175 gainers better than the 280. Rem. The 280 is more efficient on powder and you can achieve the same velocity with less powder, as opposed to a 7mm. I shoot a .280 hand loaded with 140 grain bullets. I like the 280. Always been an odd ball though.
As a point of clarification, the .280 can indeed �achieve the same velocity with less powder� as a 7mm RM, but only within the limits of the .280 Remington. Case in point, Hornady 7th lists 162g bullets at 2800fps with IMR 4831 for both � 51.7g for the .280 and 56.2g for the 7mm RM. The difference is that 2800fps is top end in the Hornady manual for the .280 while the 7mm RM has loads to 3000fps.
With lighter 120g bullets, Nosler #6 shows differences exceeding 300fps, with the advantage going to the 7mm RM.
Its really hard to beat case capacity when looking for velocity.
