Not trying to stir the pot here...but I would use it out to 300 yards no problem. I have used a 300 BO and .223 in my ARs to kill whitetail with no issues. Full disclosure they were all around 100 yards give or take. But I would use them out to 300 no problem. Now with the 6.5 you get the best of both worlds. You get a heavier hitting cartridge than the .223 but a flatter trajectory than the .300 BO. Use the 1000lb KE guideline and you should be good. In my ballistic calculator I used a 120 grain TSX BT at 2,300 FPS and at 300 yards your looking at 1,049 Foot lbs of energy. I wouldn’t go past 300 yards though.