The 280 is specified by SAAMI for 60 KPSI MAP, though I've read that commercial loads were a bit lighter, as previously mentioned.
Ackley did some experiments "back in the day" to see if the .277 bullet was capable of making full use of the case capacity of the 30-06. Since the 7mm bullet is only a little larger, .284", I think his results apply. His conclusion was that the 270 just about as well might have been made from the 308 case, with only 50 FPS loss.
The net result of all that is that the 7mm-08, 7x57, and 280 are all going to give very similar results.
The 280 is (unjustly) one of the least popular chamberings. You might be able to drive a very favorable bargain on that basis. (Set the barrel back a bit, rechamber to 7x57 and instantly become the coolest guy in your hunting group.
)