Id look for a hammer forged barrel with a 1-7 twist thats at least 16 inches.
Which reminds me, I have been meaning to get the OB's thoughts on the pros and cons of hammer forging process vis-a-vis button rifling. I notice that many don't care to spend the extra coin for a bfh.
Any of yall have experience with CCMG Uppers?
May have an oppotunity to get one at a decent price but know nothing about them