Unless you're in a DMR position, the AR-10 type rifles are going to cost you ALOT of money to feed, especially if you use good components, or good quality factory ammo...And that's for the cheaper caliber options. Price out some good .260 Rem or 7mm-08 ammo... You're looking at $35+ per box of 20. That's one magazine.
For true precision, go for the bolt-gun. And this is coming from a guy who owns an LWRC M6. Not that it's not accurate, because it is surgically accurate, but it is too expensive to shoot for fun these days, and it's only a 5.56. I haven't shot it in over a year, and that was only once, in the last 2.5 years. When I bought it brand new, Fed Lake City XM193F was only $3.79 a box (20)... That means it cost $5.69 to load a 30 round mag... But now that it costs almost $8.00 a box (20), it costs you $12.00 per 30-round mag. And that's just for 5.56....Imagine loading a whole box of .260 Rem, 6.5 Creed, 7mm-08, .308 Win, or 6mmBR ammo into it would cost for a drawn-out mag dump that lasts less than 2 minutes...
Bolt guns are also inherently more accurate due to less moving parts, tighter tolerances (because it has less moving parts), and it only single-feeds.