First, I'll admit I haven't read this whole thread.
I have shot out two barrels on a 6.5/280 Ackley, and love it. M700, 27" #5 fluted, about 3300 fps with 120 nosler BT. I can and have killed everthing from digger squirrels to elk with this rifle. One spike bull at 528 yards, blackies at over 600, many blacktailed deer from 45- 613. It's a fun gun, big for yotes, but nice in the wind of eastern Oregon.
I will admit though, since I bought my 7 RUM and got it shooting, the 6.5 has been parked.