That is a good observation, There are three kinds of M1's. The new ones made by Springfield Armory. The old ones from WW2 you can buy. And match M1 Garands made for competition.
The match grade M1's are fine with 180gr. This would be a rifle that set you back thousands or more. The new Springfield Armory M1 Garand you will not harm with a few boxes of 180gr ammo. These rifles have been optomized for 150 to 168 grain ammo and a few grains are not going to matter safety wise. The old WW2 models if you use the heavier hotter loads it is something I would not recommend. Considering you have no clue what the previous owners did with your parts it is always better to err on the side of caution. If you really want to shoot the newer loads in the older gun you can get the gas block modified for modern ammunition, or look around see if you can get an adjustable gas port.
Remi
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Oscar, Mike, Golf...the Italian walnut M14. Resolve is gone. All hope is lost. Take my money...