I buildt a 20" AR10 in 6.5 creed, but it was so heavy and awkward that I ended up swapping barrels to a 16" fluted lightweight 308 (wilson combat ranger barrel).
Honestly I'd not bother with any AR10 in a barrel longer than 16 inches
For hunting big game, Sierra 165 grain game changers will expand out to about 450 yards with a 16, and I can't really see needing more than that for my purposes.
If it's your first time around on a large frame, sticking with aero m5 parts will save you lots of headaches.
Last edited by CaptArab; 01/12/20. Reason: Spelling
