James B-I have chronographed several 7mm mags and a few 280's myself and my findings are just the opposite of your own.I have found that the 280 is underloaded due to it being chambered in some of the older remington pumps.The 7mm mag's do offer noticeable more velocity than the 280.As for the 7mm mag being the most over rated -this is not possible as the 30-06 has that title all locked up.