RE: Second Gun - big game hunting
There aint no magic laser beam thats gonna make a 600 yard kill easy in any caliber. The only way to be proficient at that range is an absolutely anal amount of practice. It isnt something you can get decent at and quit practicing at. You will have to continuously practice at that range. You are dealing with a lot of variables at that range. Theres some on here that like shooting those ranges and I guarantee you they shoot very very often.
How much are you willing to practice irregardless of caliber to consistently make good shots at that range? My advice is to take the 30-06 you have and shoot it till you are sick of shooting it and then shoot some more.
On another note Im glad to see we have some people that have never picked a 338 Win Mag up downing it. Going from what? 1 gun last year at this time to owning at least one rifle of every cartridge and makethis year?