Good to know. The question was SA, who built the rifle, said 150 factory loads will not harm the rifle.
If the gas-port pressure is too high, the op-rod/bolt assembly is essentially a miniature pile-driver pounding on the back of the receiver.
So you disagree with SA about factory 150gr loads?
The actual bullet weight is less important than the burn-rate of the powder.
It’s my understanding M2 Ball ammo is loaded with IMR4895 powder. IMR4064 was actually preferred ballistically, but its grain size/shape made it impractical for machine measuring/loading. My Garand seems to be a little more accurate using 4064, but I measure my powder charges by hand.
If factory ammo with 150-grain bullets has powder that burns at least as fast as IMR4895/4064, it’s suitable for use in a Garand with a standard non-venting gas-cylinder plug.
My suggestion would be to either use mil-surplus ammo or load your own.