Aero Precision M4E1 Threaded Barreled AR-15 Upper Receiver .300 BLK Pistol – ATLAS R-ONE – 10″


  • M4E1 threaded upper receiver
  • Forged 7075-T6 aluminum
  • Assembled forward assist and dust cover
  • 9” ATLAS R-ONE M-LOK handguard
  • Hardcoat anodized
  • 10” .300 Blackout barrel
  • Machined from Chrome Moly Vanadium
  • Pistol length gas system
  • 1:7 twist rate
  • Threaded 5/8×24
  • A2 flash hider
  • Salt Bath Nitride finished
  • Does not include BCG or charging handle


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SKUAPAR700702M4 Category

Note: This barreled upper receiver assembly has a barrel length under 16” and is therefore subject to all NFA rules and regulations. Know your local laws before purchasing.

This upper receiver assembly comes complete with a 10” .300 Blackout barrel and a pistol length gas system. The forged 7075-T6 aluminum receiver features a billet design and looks great when paired with the M4E1 lower receiver. The ATLAS R-ONE free float handguard is made from the same material with the same hardcoat anodized finish and features a lightened profile with M-LOK slots for accessories. This .300 BLK AR-15 barreled upper receiver assembly does not include a BCG or charging handle but does include the forward assist and dust cover. Build a high quality .300 BLK AR pistol today with the M4E1 upper receiver assembly.


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