I'd take a serious look at Remington Model 700 Sendero chambered for the .300 Remington Ultra Mag. They have rounds loaded for the .300 RUM at three different performance levels The mild loads equate to a .30-06 level of performance. The mid-range rounds approximate the.300 Win Mag. And, the full power.300 RUM loads surpass the .300 Win Mag by a healthy margin. Pretty neat concept.

If you really want to shoot out to 600 yards then you need at a minimum a powerful 30 caliber or larger. You will also need a good quality factory rifle-Then you will have to take it to a gunsmith for some custom work. You will also need a high quality scope with a first class mounting system. You will also need to start reloading to customize your ammo. IMO you are looking at a minimum investment of around $3,000(and that is the low end)to be able to be consistent enough at 600 yards to ethically shoot at a game animal. Tom.

Ok, I'd say .30 caliber.

Do a google search on Best of the West and look at the website. I am thinking he uses something along the lines of a 7 RUM or that effect. Used to be a pretty informative show until the host changed. I think the original host John Burns used to post here.

I agree with EKM. In addition, I don't have much use for someone who shoots at a bull elk at 600 yards or more, regardless of the cartridge in use....

I would say make it a 30 cal. if your hunting
with it.The bullets selection is really about the
best you can get..If your thinking in the lines
of target only then the 6.5x284 is a great choice.

600 isn't that far. A 7mm Rem Mag, 7mm STW, or 7mm RUM would easily take care of it. Just make sure to load them up with some good high BC bullets, either Bergers, Wildcats, or Accubonds. If you want something that will pretty much outshoot ANY factory chambering look into the 7mm Allen Magnum. I see nothing a .30 cal will do over a good 7mm, if you need something that big look into the .338 RUM or .338 Edge.

Whatever you decide on, please practice and know your limitations. Remember you don't just want to hit the animal, you want to kill it. Shooting steel plates at 600, 700, or even 1000 yards is one thing - but an animal is something different. They deserve more respect. I'd much prefer recommending getting within 300 and certainly 400 yds before even thinking about taking a shot.
I've hunted in several western states in a variety of terrain. It is tempting to attempt 600 + yd shots and alot of places it can be done. I passed up a few shots this year on an elk hunt because I couldn't get close enough for a shot due to running out of daylight or couldn't get close enough because of the terrain. I went home empty handed but satisfied. Sure I spent a few thousand $ on the hunt and maybe I could have HIT one of those elk with my 325WSM out there at 500 or so yds but I wasn't about to try. Hell I'd much rather have one 'in my face' after a 2 - 3 hour stock than blast away at him 'way out there'. But that's just my opinion.

.50 BMG should handle it

I've been eyeball'n a Rem Sendero in 264 Win Mag. The 142 gr Sierra bullet has a great BC. With the right glass, I think it would be a great rig.