The problem with long distance shooting is that when someone makes a 300 yard shot on a animal by the time that he tells the story it turn into a 900 yard one with a 60mph cross wind. I have a friend that claims that his 7mm Remington mag will shoot out to 600 yards with only a 6" hold above where he wants to hit. He doesn't believe the ballistic charts and says that they were made up so many years ago that they are no longer valid.
My two longest shots that I have ever tried were at 749 yards and 787 yards and both were checked with a range finder. The 749 yard one was on a deer on the last day of the season. He was feeding in a field with no possible way to get any closer and with me knowing where my rifle was sighted in at I took the shot with a one shot kill. The other was on a elk, same type of situation. After I took the first shot he turned 180 degrees. I asked my "spotter" if I had hit him but he didn't say a thing so I took the second shot. Both shots hit the elk right where I planned on it hitting, the first shot would of done the job but like all elk he just didn't know that he was dead.
Now with both rifles that I was using I do a lot of shooting with them at 600 yards and one of my favorite things to do with either of them was to hunt ground squirrels at a long range. I knew where both of the rifles would shoot the load that I was shooting and felt comfortable with all the shots. Now after saying that I don't think that the average hunter that goes out once or twice a year to shoot his rifle should try anything over 400 yards. Once you start to shoot where you have to use Kentucky windage to aim at you should put the rifle down and find another animal
Also as for what the military is now using for long range sniping take a look at the .50 BMG round and the .338 mags. Both are becoming more and more common in the sniping game and have fantastic long range performance. But snipers work in two man teams, one shooting and the other is the spotter and will tell the shooter what he needs to do to correct his point of aim for a hit. Even the British or Canaidan sniper that took out a target at 1 1/2 miles needed 3 shots to hit his target.