Interesting post by mattcw in the comments section of this article. I assume it's true even thought he spelled Enfield wrong.
16 March, 2023
"It’s funny how history repeats itself! After WWI, the British were developing a new round designed to be the perfect balance of soldier friendly and lethal to humans. They designed a round called the .276 Endfield, (.276”= 6.8mm) but decided to stick with the .303 round used since the 1890’s, as they had so much on hand and retooling costs. The #1, MK 4 rifle was the result.
In America, around the same time, John Garand devised a new weapon to replace the 1903 bolt action, a semi-automatic and designed it around the .276 Pederson round (.276”= 6.8mm) and it held 10 rounds. General staff decided it would be chambered in the already used .30-06 round… because we had so much on hand and retooling costs. This resulted in the M1 rifle which had an 8 round capacity.
After WWII, both militaries started looking for a lighter, still lethal round. The 7.62mm (still .30”) was used, but provided no better results. A few years later, the 5.56mm was adopted and used ever since. It has worked, but not carried the energy or lethality of harder hitting rounds. Back to the drawing board everyone went!
We are now back to what balisticians decided in the 1920’s… the 6.8mm/.276” bullet is the best solution! "
