I built mine with an Alexander Arms barrel and bolt. 20" barrel, rifle is extremely accurate. More accurate than I am for sure. It is also a great hunting caliber. Apparently Alexander Arms is no longer selling barrels, if you want one of theirs you have to buy a complete upper. Here is a pic of mine.
I don't know anything about this company, but this barrel looks saaweeet! I just found it from a quick google search.
http://www.undergroundtactical.com/products/6-5-grendel-barrel-spiral-fluted-w-bolt.html
And here is a cheaper option from the same company.
http://www.undergroundtactical.com/products/6-5-grendel-barrel-ultralight-w-bolt.html
If you decide to build your own I would be glad to help if you need it.
What suppressor are you using?