The new 6mm ARC complete and operational upper kit is here at Apache. This version uses the black Nitride coated Hex Twisted barrel version of or popular stainless steel barrel. Our pro shooter reports flat-shooting, no turret adjustments needed to at least 700 yards; just simple holdovers.
The complete upper kit is a built, operational upper receiver that instantly mounts atop your already owned AR15 lower receiver. Complete upper means it also includes the necessary 6mm bolt-carrying-group and charging handle.
Apache hex barrel in stainless plus black nitride coating, 20" barrel in the 7.5 twist is the sweet spot in Hornady's new 6mm ARC round. Designed to be effective to well farther than the 5.56 round. It's range is jaw-dropping in the AR15 platform. 

This version uses a lighter weight 15" handguard with Mlok on sides and bottom with picatinny rails on top. 

All Apache branded uppers and Apache branded functional parts are guaranteed for life within normal use, and have beed test fired for function before shipping. See warranty detailed info on website for full description.