I think the 6.5 would definately have enough punch for the game animals that you mentioned. Given his criteria, the 6.5 fits the bill pretty well. Personally, I am fully confident with mine. One question is, what kind of gun is your friend looking for. Are these 600 -800 yard shots going to be routine in matter, or just the hypothetical max? Plus, what is a lot of powder/recoil. This quesion sort of ties in with the "what kind of gun" does he want. Objectively, the 6.5 does not burn a terrible amount of powder less than some of the short mags. Heck, my 7 Rem eats 61 or 2 grains of powder, compared to my 6.5 which takes 50 grains. Granted, a 20% increase in powder is significant, but if your plopping down the money to build a 6.5-284, it should'nt be too burdening. Now on recoil (and this ties into range), if one were to build a heavy enough rig, then a magnum wouldn't kick all that bad, and it would definately have the legs for an 800 yard shot(plus added stability etc). So, before getting set on the cartridge, I would tell your friend to evalute a little more on how he is going to use this rifle. 800 yard shots are a good start, but is this going to be 800 yards after hiking 6 miles, or from a rest close to the road? I would weigh those factors just as heavily as I would the cartridge. That being said, I like my 6.5.