The M14/M1A is, functionally, a Garand action for a shorter cartridge and a removable box magazine. It’s the result of John Garand himself telling the DOD (formerly the War Department, back when we used to flat-out win wars) that there was no way to achieve a full-auto rifle with a full-powered rifle cartridge with a .30-06 in a 10lb rifle. There’s just no way. If you review the historical accounts of the M14 project, you find that Garand was no dummy – he told the Army brass that we needed an “intermediate” power cartridge like the 8mm Kurtz or something similar to achieve full-auto fire in a 10lb rifle. But the Army brass . . .
…Not to be deterred from their damp dreams of a full-auto rifle in a full-powered “gravel belly” cartridge, barely listened to Mr. Garand and conceded to lower the power to what we now know as the .308. Which is really just a functional equivalent of the .300 Savage… but no further. We’re talking of only about a 200fps reduction in muzzle velocities from a .30-06 in 150gr bulllets. Where the cartridge really needed to go was to something like .260 or 7mm08 at 2600 to 2800 fps and a 120 to 130 grain bullet and I think .260 Rem would have been vastly superior to anything we got in the .308… and even more vastly superior than the 5.56 poodle-popping cartridge.