6.5 Grendel SBR build - questions/comments?

I am curious as to experience with this cartridge for a 10.5 - 12" SBR build…

14.5" ballistics seem quite impressive and I would appreciate feedback - according to AA .pdfhttp://alexanderarms.com/grendel_ballistics.pdf

Anybody have experience with any decent 6.5G flash-hider/muzzlebreaks?