I have a load for my old 7mm RM that shoots a 140 gr. Nosler BTBT right at 3400 fps.. About 300 to 400 fps faster than the .280.. Not all 7;s will do this, but this one has a 26 inch barrel and a long Remington magazine..
I'm curious to your load, it seems warm and in 7mm STW or Weatherby territory. Most 280s are 22" barrel so you're probably gaining around 150 fps with your 26". The 7 RM is faster, but all things being equal, the 280 is not giving up much.
