Some people here won't agree with what I'm going to say, but I don't want to see you lose deer or have to trail one for half a mile or more. I've already had to trail antelope on more than one occasion with the 6.5, with a perfect hit at under 200 yards(not from my rifle). Nearly all of the softer (cup and core) bullets lose the ability to mushroom effectively below about 1500fps. That's true for .243 cal up to 30 cal. The larger calibers have even heavier jackets, and will pencil through a Whitetail deer at speeds below around 1800fps(exceptions being some of the 180 and 200 grain .338 bullets and the Sierra 225 grain .358 bullet). But they start with larger entrance wounds and still make exit wounds that exceed .35cal just due to their original diameters. A .264 cal bullet at 400 yards won't create a large temporary or permanent wound channel because it has lost velocity and impact. Impact and broad wound channels are the result of hydrolic and Hydrostatic shock, and below around 2200fps, the smaller, lower massed bullets have lost most of their ability to create the shock wave in tissue needed to create this effect. A 30-06 at 300 yards with a 180 grain high-BC bullet launched at 2750 fps will have you blood-trailing a big Whitetail about 30% of the time, and it has much better penetration, impact and wounding capacity than any of the medium velocity 6.5mm cartridges. Bullet construction has a big effect on killing capacity, too. A bonded bullet is great if you're launching it at 2850 or above, and expect to have it hold together through heavy bone at around 40 to 150 yards. At 600 yards, nearly all bonded bullets and mono bullets will fail to open up due to their heavier construction. However, a standard bullet launched at around 2750fps will hold together at close range and at a distance, even through a Whitetail's shoulder if it is heavy enough. It will also mushroom at a lower velocity than any of the 'premium' bullets. I would limit my shots with the Creedmoor to around 400-450 yards, and use either Speer, Sierra GKs or Nosler Ballistic Tip bullets in their heaviest offerings. They all offer a 140 grain hunting bullet, and their BCs are all bove .5 or better. If you want to go farther, either up the bullet diameter or go with a higher velocity offering, or both. Killing doesn't come from speed only. It comes from a combination of speed, actual mass, diameter of the bullet, and matching the bullet construction to the game. Also, keep in mind that foot-pounds per Sq. in. is a little deceptive. for instance, and 22-250 launching a 50 grain bullet at standard velicities and a 45-70 launching a 405 grain factory round have about the same ftlb rating. No-one is going to argue that the 22-250 is going to be an effective bear round, while the 45-70 is decidedly so.