"...if pressures too high..." There's no laboratory documentation of any M1 Rifle being damaged by the ammo alone. Only second or third hand anecdotal evidence. And that did not appear, anywhere, until the Internet came along.
What
is documented is JC himself testing the rifle with ammo he loaded that went up to 125,000 PSI. No damage to the op rod at all. At 125,000 PSI, the left locking lug cracked. The same rifle, with no repairs, fired another 5,000 rounds of service ammo with no further damage of any kind.
There's also the one about how using a heavier than 180 grain bullet will cause damage. John R. Clarke wrote a reloading for the M1 article in the March 1986 issue of American Rifleman magazine. Wherein there is load data for 190 and 200 grain bullets. Nice Matchkings too.
https://www.scribd.com/document/4085...Rifle-J-Clarke