I have a Ruger American Predator in 6.5 Creedmoor with a SWFA SS 12x42 scope mounted low.  
_{When I have the money, I'll upgrade to the best scope I can afford around $600 since I'm kinda doubting 12X will be enough for me to see much further than 500-600 yards (I know they say 1X per 100 yards, but I'm 46 with glasses due to an astigmatism). I'll likely also get a magpul chassis for the gun and a range finder (I know the barrel is only a mid-size 22", but I like that it's fairly light and handy for the few hunting trips I tag along on).
I've seen youtube people make 1000 yard shots with worse equipment, but I'm a newbie to bolt guns (I've been shooting ARs from 50-300 yards for 21 years); I'm still reading up on the ammo (mine will be Hornady 140gr ELD Match), the scope with mil/mils, and all the other details (20MOA mounts vs 0MOA mounts, etc.).}  

** What I want to know is, factoring in VERY LITTLE wind (<5mph), if I zero the gun at 100Y (or 200Y), and figure out how many mils I need to dial (or hold-over), can I pretty easily make hits on a 18" gong or IPSC torso at 500Y if the gun is steady on sandbags and I'm good on the trigger (without having to walk it in)?  How about 800 yards?  I assume 5mph wind could throw the round left or right by 5-6" at 500, and more like 12-15" at 800.
At what point does 6.5CM become tricky for people who aren't great at reading the wind?  For instance, the AR with a 50Y zero and a Leupy 1-6X CMR-2 reticle, is easy to shoot out to about 300 yards for me using a BDC, BUT I'm sure bullet drop and the wind acting on a 77gr bullet would make it VERY difficult if I tried to go to 500 or 600 yards even though it's done every weekend by guys at matches (though I'm sure I could "walk" it in after a few shots).  NOTE:  I haven't had access to a range past 300, but am planning on going to some land where a guy has 1200Y to see what the 6.5CM can do.

damn less than 5mph wind? Here it is at least 10-15mph and not a breeze till it hits 20mph. Granted doesn't effect much at 100 yards like it would 200-600. Although range here does have 600 yard range I just do not have anything that I would shoot at that range. I have talked to a few here that like to shoot at that range and they all say really just depends on which way the wind is blowing for how you are shooting. They range faces east/west which is typically where our end comes out of for the most part. They said north/south then really have to factor in the hold for the wind.

Yeah, I was going with best case scenario (or hoping that crosswinds might help cancel each other out).
That said, certain times of the year it seems like there's very little wind--the insane Florida heat and humidity probably makes the air not want to move. It sure makes me not want to move (certainly no faster than 1-2mph).   :)

I've shot mine out to 1800 yards many time. The range your talking will be a walk in the park. Wind is the great skill that separates the men from the boys. If you cant call wind your going to struggle tell you do.