If that were the case, wouldn’t we have the FAL in .280 British?
If we adopted the .280 British (7mm NATO) after WWII, maybe we would
still have it, instead of going from .30-06 to 7.62mm NATO, then all the way down to 5.56mm, then back up to 6.8mm. Oh look,
the U.S. military's shiny new, latest and greatest cartridge is 0.007" smaller than the .280 British and
it's performance is absolutely magical if you listen to what they're saying about it. Too bad the .280 British itself just wasn't good enough, but somehow the 5.56mm poodle shooter was good enough for over half a century - until it wasn't and they needed something closer to .280 caliber.