So many variables- Is the deer standing in good light, does the shooter have good eyesight, does the scope have a lot of parallax... A good shot with iron sights on a day with good light can keep all his shots in a six inch circle at six hundred yards- Theoretically, a six power scope should double or triple that range, but it doesn't because so many other variables come into play. I don't think it's too far off to say that a six power scope will take almost all people past the capabilities of both them and their rifles. On deer especially, once you get past 400 yards or so, there is such a likelihood of that deer taking a step between the time you send the bullet and the time it gets there that it makes those shots pretty iffy. I say that knowing there is a handful of hunters here with the experience and discipline and animal knowledge to wait until everything is perfect before they drop the hammer. This is a pretty vague reply, but the question doesn't lend itself to a precise answer.
