Well there's one way to find out......do you have a range around close by. Please keep this in mind if and when you shoot it. These Garands should not be hot rodded. You will need to find some tame loads for it. Everyone all of a sudden wants to get the latest hot loads for their deer rifle and I can add, the dead deer doesn't know the difference between 2750 and 2950'/sec but that old Garanddoes. Hot loads are a no no.
Added. No reason to over tighten the gas plug. I have a big phillips I use on mine. You can snug it down pretty tight if you clean it after shooting.