White Oak Armament.
They have a background shooting at the national matches and make some great barrels, at good prices. I have used 20+ of their barrels for builds for other people, as well as myself, and have yet to have one that will not shoot .5 moa with proper handloads. A good number of the guys I built them for were running standard MK262 77 grain smk, and the barrels shot the 262 very well.
This was a test target from an SPR using MK262 :
I am quite sure if you handloaded you could really tighten this up, but considering that is roughly .5 moa from military match stuff, it is likely sufficient for most applications.
I think I still have 3 of their barrels sitting under my bench right now from a big order I did a while ago. WOA is good stuff.