I think there are some differences in a 270 and a 280,but they are fairly subtle.
I have owned more than a dozen of each through the years,all factory rifles,and on the average the 280s have been more accurate with factory ammunition.This may be because the rifles and loads for a 280 have been manufactured in smaller lots,or it may have been luck of the draw,but it has been my experience.
I have only owned one 280 factory rifle that would not put three factory made bullets from a cold barrel into a one moa group at 100 yards. It was a boat paddle stock Ruger M77,and it shot a lousy 1.25 moa.
On the other hand I have run across more than one 270 that was hard pressed to shoot into less than 2 moa.
Not to say that wonderfully accurate 270s do not exist,I have a couple of them myself.
The other difference in my view relates to typical bullet construction in 270 vs. 7mm bullets. On the average 7mm bullets have been more likely to penetrate deep and exit on game animals. I think they are built a little tougher because most are intended to be used at 7mm mag velocities.
