This is a Grey Ghost Precision Upper known as the Forged Upper chambered in 556NATO, model GGPCUR.
Finally you can grab what Gray Ghost Precision considers the best forged upper in the biz" and it is a perfect companion for your GGP Cornerstone Lower receiver. After all" accuracy comes from tight" precise tolerances that minimize all variables from the moment the hammer strikes the firing pin until the round leaves the muzzle. By perfecting the critical tooling dimensions to the smallest degree" a forged receiver can punch the same hole down range.
Features:
Machined to tighter than Mil-Spec tolerances, the critical tooling dimensions are held to within +/ - .001";Machined from forged 7075-T6 Aluminum;Black Hard anodized with a surface hardness of 60 Rockwell