if you would like more insight into using the .308 as a long range round, check out Longrangehunting.com and do some searching. Ian McMurchy (outdoor writer) posts quite a bit on there and he has used this round for years in culling deer at extended ranges out west.
Accuracy (the ability to put the first shot right where you want it) every time is the key. If you shoot a 150g bullet through an animals vitals, it doesn't matter if it's 50yds or 550yds, it's still dead.
Good luck and keep us filled in on your adventures.
And welcome to Hunt Chat.