Compatible with any milspec AR-15 lower receiver.
Assembled by our gunsmiths at Angle of Attack Arms, this complete upper utilizes CMMG's bcg/barrel combo.  The dedicated 5.7x28mm 16.1" barrel made from 4140CM steel has a 1:9 twist and a 1/2x28 threaded muzzle. The blow back operated bolt uses CMMG's patented Radial Delayed Blowblack operating system. Giving this upper reduced recoil and enhanced safety. 
 
We added a stadard birdcage flash hider, an ambidextrous charging handle, and a 15" free float MLOK handguard. 
 
Ships with 1 32 round 5.7x28mm converted magazine that fits any stardard AR-15 magwell.