The Garand was designed to be a ten-shot 6.5mm, I believe.
This was changed to 30-06 and eight shots due among other reasons to massive stores of that ammo.
We missed a golden opportunity switch to the “just right” caliber.
(Wiki)
Twenty gas-operated .276 T3E2 Garands were made and competed with T1 Pedersen rifles in early 1931. The .276 Garand was the clear winner of these trials. The .30 caliber Garand was also tested, in the form of a single T1E1, but was withdrawn with a cracked bolt on 9 October 1931. A 4 January 1932 meeting recommended adoption of the .276 caliber and production of approximately 125 T3E2s. Meanwhile, Garand redesigned his bolt and his improved T1E2 rifle was retested. The day after the successful conclusion of this test, Army Chief of Staff General Douglas MacArthur personally disapproved any caliber change, in part because there were extensive existing stocks of .30 M1 ball ammunition.[14] On 25 February 1932, Adjutant General John B. Shuman, speaking for the secretary of war, ordered work on the rifles and ammunition in .276 caliber cease immediately and completely and all resources be directed toward identification and correction of deficiencies in the Garand .30 caliber.[12]:111
The British went through a similar process prior to WWI. They designed a Mauser type action with a .276 caliber cartridge.
They cancelled it due to the same reason, a huge supply of .303 ammo plus the rifles to shoot it in.
It did result in the pattern 14 Enfield which eventually became our 1917 Enfield. One of the strongest actions ever.