For O'Connor, the .270 Winchester and the .280 Remington were essentially ballistic twins; the only real difference being that Remington loaded the .280 "with pressure low enough to function in an autoloader but to give an approximation of .270 ballistics".
Regarding the comparisons between the .270 and the .280 being made at the time, in his book The Hunting Rifle, O'Connor concluded, "...The .280, good cartridge as it is, has not set the world on fire as far as sales go, and as this is written (copyright 1970) Remington has stopped chambering any rifles for it. The answer, I believe, is that the .280 is too much like the .270. The magnum boys wanted something hotter and noisier and the .270 enthusiasts were happy with what they had...
" Of the (two) cartridges, the .270 is loaded to the highest pressure, as for years nothing but good strong bolt-action rifles were made in that caliber. S.A.A.M.I. specifications for the .270 call for a mean maximum pressure of 54,000 p.s.i. The .280, because it was designed to be used in an automatic and a pump-action rifle, is loaded to a maximum pressure of 50,000 p.s.i. DuPont owns Remington and the hottest loads given by DuPont for the .280 run 50,000 pounds. Anyone loading for the Model 742 autoloader or the Model 760 pump should stay at 50,000 pounds or below. A bolt-action .280 can be loaded just as hot as a .270 and will do about anything that the .270 will do."