There was a issue Remington did have some Remigton cartridges loaded to lower pressure involving ones loaded in the 740/760 guns.. Myth or not they are loaded lower to this day.
Actual history: Remington brought out the .280 Rem in the 740 auto to compete with the .270 Win at lower pressure. Until the Weatherbys were standardized, .270 was the hottest factory load in the country. So they specified the .280 at the same chamber pressure as .30-06, which the 740 was designed for. As far as I can tell, that was the only cartridge that was tailored to the 740.
When they temporarily renamed the .280 as 7mm Express, the advertising gave the impression that it was more heavily loaded but it was not. Worse, store clerks and once a year hunters had trouble telling 7mm Express from 7mm Magnum and there some wrong ammo complaints. So they went back to the .280 label.
By the time they jazzed up the 742 to become the 7400, they figured it would hold up to .270 pressure and built them side by side with 7mm Express/.280s. When the auto was upgraded to the model 750, they dropped the .280 altogether.
They offered the 760 pump in .280 just to round out the line, it had been available in .270 from the start.
As I said, the .257 Roberts +P has the same maximum pressure as the .30-06 and .280; a bit less than .270 or .308 and is not something to be worried about in a factory gun of any make.
Every gunzine writer in the country will tell you that the original .257 Roberts was lightly loaded because Remington was worried about factory loads finding their way into wildcats built on Spanish Mausers and low number Springfields. I doubt this because the .257 Remington Roberts
never was a wildcat. The wildcat .25 Roberts (two different versions) were not the same as and not interchangeable with the final production cartridge.