Re: 6.5 X 284 to one mile
Ashland, the 6.5 x 284 will romp it in with 139 Scenars. Even my 260Rem shoots well to 1 mile with the Scenars. Though subsonic at that range, the Scenars are still stable and smack the steel point first. I'll be trying the 140 A-Max and Berger VLDs next to see if they also remain stable.
Inputting accurate data into a good ballistic program (with G7 BCs) will have you on target within a couple of shots but it will definitely help to have a large back board too, especially if there is much wind to contend with.
After firing the shot at that range you have time to settle the rifle, watch the trace, spot the hit, call the "hit" to your buddy, then listen for that satisfying "CLANG" that seems to take forever.
Have fun.