My opinion - - -> While you can get an AR "almost" as accurate as a bolt gun,the accuracy attained will cost you a lot more money. Same bolt guns come with a great trigger and that is one of the weak points of accuracy in an AR.
Do not allow yourself to get "tunnel vision " for the 6.5Creedmoor. It is a "fad chambering" that will soon pass to another answer to a question that has been asked and answered quite a few years ago now. How to hit targets at 1000yds can be done by quite a few chamberings nowadays.
If you do not reload,some chamberings will be quite a bit more expensive to shoot than others. Case in point . . . 6.5C.
Where will you shoot the extreme distances ?? For hunting or target ?? IMO for hunting,350yds is a fairly long shot. Of the hunters that I know,or have guided,only about 3% of them have ever taken an animal at some extreme,fairy tale distance. Most of the time,while hunting,the distance can be closed if the hunter wants to take the time to do so.
Soooooooo . . . all in all,think 308Win or 223/5.56. Both are true 600yd guns and tons of critters (2 and four legged) have been killed at even greater distances with both. --- SAWMAN