308 isn't a great long range cartrige anyway. Fucking rainbows man. Sure, it has good barrel life and the design of the cartridge lends itslef to accuracy etc, but lots of trajectory and time for the wind to get at it. Someday, get a bolt gun in 243, 270, 7mm mag, etc if you develop the skillset for it.
Only the best of the best SOCOM types can get 1rst round hits at >500 yards most of the time, w/ 308 anyway. I am talking about the best of the best of the best who happen to have mad talent at dealing w/ wind and have been able to develop it. Usually, a body has to shoot, observe impact and then make adjustment, artillery style. Helluv a lot easer and faster to do this w/ a semi auto. The guy who wins is the guy who gets rounds on target fastest.
If you want a rifle to make hits at ranges >500, get an a r15. Less recoil, lets you observe impact and adjust more quickly, the gun will be of managable weight w/ a scope etc. After you walk rounds into the guy's COM at 500 yds, even if it takes him a little longer to die, he is not going to get to you. Yes 308 bucks the iwnd better, but w/ 556, once you miss ans see where your POI is relative to the POA, just adjust and make a connection. This process is faster w/ a 5.56 than a 308, especially a 308 bolt gun.
308 is great for CQB, particualry where you are defending from a more or less fixed fortified position and you don't need to be light and have lots of ammo for suppressive fire so that you can manuever in assault or retreat. The 308 is great b/c w/ certain bullets, it really drops a motherfucker DRT, which is more important the closer he is to you.
Run a scoped AR15 for longer ranges and for assault and for dismounted ops, run the 308 w/ a T1 optic for CQB when you are either defending, ambushing, or attacking w/ surprise.