I'd consider the .308 minimal for beyond 1000yd (I do like mine). I am not sure the 7-08 would be that much better. I got the 6BR because of recoil. Didn't care for the kick from the heavier .308 bullets, but, I don't care about terminal ballistics either.

What about a .30-06. Gives that bit extra for heavier bullets with better BC but not as 'harsh' as the .300WM.

But, I'd probably lead toward something like the .284 (again, less recoil and better BC). If you want sniper type terminal performance then you'd want heavier bullets and higher speeds at range. The .284 is kinda middle ground between the 7-08 and 7RM. And then there is the 6.5-284.

As someone kindly reminded me, a barrel is a disposable item. If serious about it, buy two or three so you have back ups. :) Even a .308 gets worn out.