Jimro, none of the USN modified and rebarreled M1 receivers, bolts, op rods or other parts suffered in any way from thousands of rounds of Mexican match or stiff 190 loads at or very close to proof load pressures. Both of the ones I had rebarreled were checked for headspace as a safety thing after about 2000 rounds of 190's and Mexican Match and another 3000 rounds of M118 match ammo. Headspace didn't open up at all and no op rod problems. Some of the USN receivers were magnafluxed after going through 3 barrels firing such loads in each; no cracks at all. That's one things that'd amazed me about Garands.
US Navy Distinguished Marksman Badge 153
Former US Navy & Palma Team Member
NRA High Power Master & Long Range High Master
NRA Smallbore Prone Master