Greg, I do shoot a 6mm (.243) it is in 6mmbr and I limit it to 700 yards on game with 107 SMK's. It has taken antelope and yotes at this distance on several occations. I feel your rifle with proper drops and wind dope would be a consistant killer at this distance and even to 800 with your added velocity on deer sized game. Would it take a deer at 1000? You bet, but I prefer a much heavier bullet at that distance. Game past 1000 yards I will be using my .338 with 300 gr bullets. That is my personal choice.
Greg, I am not in a class alone here nor do I feel I am. I have shot with many shooters on this site and many are great LR shooters. Let me tell you that BignGreen is no ameture. And neither is his wife. A few weeks ago at a long range shoot. I looked through my scope at the 12" round steel target hanging at 880 yards. There were hits all over it. I said " Man, some one has been wearing that 12" steel out" BnG said, yeah, my wife..
My point is, it is real, and it can be very consistant. The trick to not wounding game is this. and I quote Shawn Carlock from his advanced class. "If I do not feel I will be amazed if miss this shot, I will not take the shot at game"
Below is a target from one of our shoots. In fiels conditions where every shooter got one shot. The point of aim was the white corner of hair. The target was at 757 yards. As you can see all of the hits were in an area to kill the goat. Two shooters missed completely. Pretty good odds for some guys from this site just having fun. I was the lucky guy with a .338 LM in the hero pic.
If you stick to LR shooting and aquire good equipment that works for you, you will soon see how effective you too will be at 1000 yards.
But you are correct, it does take pratice, and lots of it.