I've been working with a custom AR-15 upper in 6.5mmBR. So far, the sweet spot load has been avoiding me, at a max load of Varget the best I can do is maybe a 3/4" group at 100 yards. I've tried the 123gr SMK, A-max and Scenars. I'm going to start loading down in stages to see if I can find the accuracy node. Then I'll have to open up the gas port a bit, it has a standard mid-length port and it barely cycles. This thing is a lot more work than a bolt gun to get it to shoot. If I ever get it figured out its going to be a lot of fun. I've been tempted to call GA Precision and LaRue Tactical to see if they will build one of their AR-10s in 6.5x47, GAP builds them in 260 already.