Even if I was able to shoot at 1000yards I would pick a 338 Lapua over 50cal.
Yup. And at "only" 1000, I'd probably take the .300 Win Mag over the .338.
Plenty for that range...and cheaper to shoot.
But since the OP has his mind made up on the .50...
Do a search over at S.H. on this topic...a ton of information- and opinions....