Hi Vapo,

Of the actions mentioned, and if he doesn't mind the money...get the Remington 40-X. For 600 yards with regularity on targets that small suggest to him look "real hard" at the 6.5/284. Even with 6.5's the wind will be a major player at those ranges.....and any caliber less than that ?????. There are quite a number of shooters meeting with great success at 1000 yard matches with the 6.5/284. And in a heavy barreled 40-X the recoil will not be significant!

Best of luck!