IMO, you'll have a hard time beating a 308. 308 is a good all-around performer, it'll handle anything from elk to prairie dogs. I prefer 7mm, but you said no 7mm/,284" bulets. 6.5mm just don't do it for me. Call me old school, I prefer heavier bullets. Years ago I had a 6.5-06. It shot as flat as a string but just didn't give me the warm fuzzies, I've always been a 7mm guy. And before somebody starts in with blah blah high BC, blah blah more energy at 1200 yds, etc, you can get high BC 7mm and 30 caliber bullets too. And the great majority of shooters have no business shooting animals way out there where the BC makes a difference. So IMO, go with a 308.