I'm a big fan of Wilson Combat and their match grade barrels (fluted, or unfluted, it doesn't matter). Last year I had them build me a 16" upper chambered in 300 AAC Blackout for taking pig and Axis deer and what I received is a sub-moa tack driver. Their custom shop is great - they installed my Geissele rail and barrel nut and still certified it as a complete Wilson upper covered by their warranty. Sure it was a bit pricy, but I couldn't be happier.