The 7mm Rem Mag., as with many other ctgs., failed to achieve published ballistics. Something on the order of 2,860fps with 175gr., which is just about achieved by the .280 Rem. IMP.
On the other hand, my old 1970 Hodgdon manual has the 7 mag pushing 175's at a top vel. of 2,938fps with H570 (discontinued) and 2,918fps with H870.
There may be other powders today, like Magnum and H1000 that will push them to just over 3,000fps.
My newest Hodgdon Annual Manual lists only 2 loads over 2,800fps, one with IMR 7977 @ 2,822 and IMR 8133 @ 2,879fps.
So, yeah- I was never impressed by it, although I did try it twice. Back then, the best powder was H and IMR4831 for just over 2,800fps.
Today, those two powders are listed at 2,660fps and 2,710fps with maximum listed loads.