What the USA should have built was a “miniature” M1 rifle that would accept a 20-round magazine & in a cartridge of the size/power of the .250 Savage.
(By 1947, BERETTA was converting M1 Rifles to 7.62x51mm, which is VERY similar to the “old-school” .300 Savage cartridge).
Yours, ex-cadet
I think.300 Savage was more equivalent to the 30-30.