The Navy made M1 Garands in 7.62x51 in the 60’s instead of buying new M14’s. Only thing that changes is the barrel. I have 3 garands in 308 or 7.62x51. The real advantage is cheaper ammo and slightly less recoil. No one has made surplus 30-06 since the early 80’s so that has pretty much dried up. The CMP offers both 30-06 and 308 garands and barrels for both.