Am I the only one who thinks the .276 Pedersen or .276 Enfield should have been adopted a century ago? Or the .280 British at the end of WWII? I think it would have saved us a lot of trouble, switching from .30-06 to 7.62x51mm, to 5.56x45mm, almost to 6.8 Remington SPC (.277x43mm), to .277 Fury or 6.8×51mm Common Cartridge.
The .276 Enfield (7×60mm), designed in 1912, with a 165 gr. bullet at 2,785 ft/s developed 2,842 ft⋅lbs of energy at the muzzle. That's more powerful than the 7.62x51mm with a 147 gr. bullet at 2,800 ft/s developing 2,559 ft⋅lbs at the muzzle. A heavier bullet with better sectional density, at nearly identical speed and a good 11% more power, all 42 years before the 7.62x51mm was invented. They could have improved the cartridge without changing bullet diameter again and again, and still been using it today.