I will be building my first longrange hunting rifle. I have been researching calibers for about 5 months now. I still cant decide. I am looking at shooting whitetail maybe up to 800 yards. (I prabably wont be shooting that far but want to be able to for some day) The think that is making the choice selecting this round is barrel life. I would love to get a 300 rum or a 7 stw but I know that barrel wont last too long. I was thinking the .243 AI and shoot 105 amax's or 117 dtac's or some other high bc bullet. I just wasnt sure if this would have the knockdown power needed to cleanly kill a whitetail at that range. I was thinking 6.5-.284 but this goes back to barrel life. I was thinking .308 but this doesnt give me the tragectory I want. So I was thinking maybe a .300 win mag. The barrel life isnt horrible on this. I could shoot heavy high bc bullets out of this better than a .300 wsm. The only think I am not liking is the belt. I was thinking about making the chamber tight fit and neck turn so that resizing wouldnt even be necessary. I dont know if this is possible with the belted magnums is it? Also what about a 7 rem mag. I know this has pretty good balistics but it is also a belted mag. Also how is the barrel life on a 7 rem mag? Any other recamendations? Thanks alot