CMMG Varmint Upper is 5.56x45 NATO chamberd and the bore has a 1:9" rate of twist. Upper is built with a standard forged A3 receiver with M4 feed ramps. 24" stainless steel bull barrel. Each barrel is head spaced and test fired before shipping. Includes a low-profile gas block, free float tube, bolt carrier group, and mil-spec charging handle. Made in USA.