Although you said you were thinking about a 308, since you didn't sound 100% sure, I'll throw this out there: instead of a 30 cal, you might check into one of the 6mm or 6.5mm calibers, like a 6 or 6.5 Creedmore, 6x47 or 6.5x47 Lapua, or a 260 Remington. I believe that some of these are offered in AR type weapons, if you want to go the semiauto route. Some, if not all, of these calibers offer better ballistics and less recoil than a 308. Just my $.02.