I'm also new here and new to the long range game.
I've been thinking of getting a .308 and topping it with a Nikon m-308 scope. It is made for the ar platform, but the recitle is more specific to the caliber than the platform. If i were to recomend a scope to you it would be the m-223 4-16 bdc 600. It will have the recitle matched to you caliber, and you can verify it by using the spot on software.
Here is the link for the scope:
M-223 4-16x42 BDC 600 from Nikon
Also, this one has the turrets you can set, if you prefer to make the adjustments for long distance. Personally, I think that 600 is about the limit for this particular caliber, and you should do just fine with the bdc 600.