The 308 or 30-06 will work on any North American game animal, from as far away as you can hit them. The problem is not the cartridge, but rather the shooter. In my opinion, 400 yards is strecthing it just a tad. I personally limit myself to 300 yards or less. I can confidently hit a grapfruit out to the range, from a field position....so, I figure I can cleanly harvest a elk, deer, or whatever. Of course, the 300 Winchester Magnum is flatter shooting and has more power. The problem is shooting it well. Not that the 300 is inaccurate, it is in fact very accurate. I have trouble enjoying shooting anything much bigger than the 30-06. This causes me to not want to practice with it. When I say practice, I mean burning several hundreds rounds...not just zeroing your scope. The further you wish to shoot, the more you need to practice. My rifle rarely goes more than a week without being fired.

One of my biggest fears regarding long shot is not that I can not hit, but rather the time it takes the bullet to reach said target. How far can a deer move when you shoot at him from 400 yards away? Also, one must consider wind. Wind causes me more frustration than bullet drop ever has.