Nathaniel Fitch blogs about the wisdom (or lack thereof) for having a single general purpose cartridge that can satisfy the needs of riflemen, machine gunners and sharpshooters to replace both the 5.56mm NATO and 7.62mm NATO …

The first group of cartridges all greatly resemble (though none improve upon) the .276 Pedersen. These include the7x46mm UIAC, the .270 Sidewinder, the .280 British, and others. The second-most mature group, many have examples have actually been loaded and fired, and the .280 British was even officially adopted, briefly. Because their performance has been verified, it cannot be said that these cartridges are unfeasible, but is it worth the cost and effort to field one, in light of the widespread adoption of 7.62mm weapons? In a word, no. Even the literature for 7x46mm UIAC shows it’s not greatly more efficient than 7.62 NATO, and it doesn’t provide any additional capability, so why would military procurement spend millions re-arming with entirely new weapons and ammunition when they have almost-as-good-and-already-in-the-inventory 7.62 NATO machine guns and rifles? Since these cartridges are also almost as heavy as 7.62, they offer little practical benefit and will be largely passed over.

Many thanks to Sven (Defence and Freedom) for emailing me the info.