Yes, the .270 eventually resulted from the .30-03, but there was a stop along the way. After the Springfield became the U.S. military rifle, Winchester could see the coming importance of the bolt action. They developed their own bolt rifle and planned to first introduce it in Europe, for some reason (they always did have something of a presence in Europe, partly die to John Browning).
The rifle was in the works around 1912, and very much resembled the eventual Model 54, with a European-style Schnabel-tipped stock. The cartridge was essentially the .30-03 necked to take a .288 (not .284) bullet.
But during the plans to start commercial production something eventually called World War One broke out, and the project was scrapped until after the war. Europe was so messed up by then that the rifle became the Model 54 Winchester and appeared here. The new cartridge's bore-size was changed to .277, reportedly to keep people from rechambering the many pre-'98 Mausers in 7x57 then becoming common in the U.S., due to so many coming across the Mexican border. Their actions weren't considered strong enough for the new Winchester cartridge.
