Aero Precision APAR700725M53: Upgrade the performance of your AR15 build with this 6.5 Grendel Complete Upper Receiver. Designed to be a low recoil/high accuracy cartridge, the 6.5 Grendel is ideal for those looking to stretch the legs of their AR15 rifle, with proven results at 1000+ yards. This complete upper includes Aero Precision\'s new ATLAS R-ONE Handguard! The R-ONE handguards are designed with size and weight in mind, while still providing plenty of real-estate to accommodate any attachment needs the end user may have. Aero Precision\'s proprietary ATLAS attachment system is a durable and dependable mounting platform, maintaining a slim profile while still providing the strength and stability customers have grown to love from Aero Precision handguards. This upper assembly DOES NOT include a BCG or Charging Handle. Includes: M4E1 Threaded Assembled Upper Receiver 15\" ATLAS R-ONE Handguard 6.5 Grendel 20\" Stainless Steel, Rifle Length Barrel .750 Low Profile Gas Block and Rifle Length Gas Tube A2-style Flash Hider Product comes assembled The 6.5 Grendel is designed on the AR15 platform. You will need to purchase a 6.5 Grendel specific bolt and magazine. All other components are standard to the AR15 platform. M4E1 Threaded Upper Receiver Features: New enhanced forging that gives the upper receiver a \"billet look\" New picatinny profile that blends seamlessly with our Enhanced Series Handguards M4 Feedramps .250 takedown pin holes Laser engraved T-marks Includes port door and forward assist installed ATLAS R-ONE Handguard Features: Full top picatinny rail for optional attachments Quick disconnect sling socket at the 3, 6 and 9 o\'clock positions Compatible with low profile gas blocks 1.3" Inside diameter 1.5" Outside diameter Compatible with mil-spec AR15 upper receivers and barrels 6.5 Grendel 20\" Stainless Steel, Rifle Length Barrel Features: 6.5 Grendel 20\" Rifle Length Barrel 416R Stainless Steel finish 1/8 twist 5/8x24 Threaded Pitch DMR Profile .750 gas block journal Rifle length gas system M4 Feed Ramp Extension HP and MPI tested