Re: Which is most accurate out-of-box?
The caliber doesn't have the 'wow' factor but the FN SPR A3G is unbelievably accurate. They have a 1/2 MOA guarantee for 10,000 rounds. I've not heard of any that shoot 1/2 MOA, they're in more cases than not much more accurate. Out of the box for under 3k. Bedded by GAP, ops inc rail, chrome lined barrel. Mine came with a .210" test target but often does better than that. Many groups are in the 1s. Most are in the 2s and 3s. My best ever was .24 at 300 yards.
Long range shooting is a process that ends with a result. Once you start to focus on the result (how bad your last shot was, how big the group is going to be, what your buck will score, what your match score is, what place you are in...) then you loose the capacity to focus on the process.