The 6.5 with good optics will get you out to 1000 yard and probably a little beyond. The 308 is a little better at 50y to about 200y in terms of precision accuracy. 300-400 yards, almost identical. Out past 500-600 yards the ballistics on the 6.5 take over and I think gives you a 15% better hit probability. Now with heavy winds, I would go for the 308 175-190 grain for the longer shots. Where I shoot the wind swirls when there is wind, so all bets are off. As far as optics, I see a lot of my buddies with that Vortex Razor HD gen II 4.5-27 x 56, You could go Nightforce for 3x the price, but the Vortex will do the job. I find my 20x Leupold is pushing it at the 1000 yard range. Long range shooting is a great hobby, a tad expensive, but cheeper that a Ferrari.