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Rainier Arms Mountain - Stripped Upper Receiver Group CHF Barrel

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Rainier Arms Mountain - Stripped Upper Receiver Group CHF Barrel

As low as $299.99 Regular Price $499.99

Our Rainier Arms Mountain Series upper receiver group was designed for the enthusiast that's looking for a solid foundation for their next upper build using our 1:7 twist Mountain series barrel, our Mil-Spec upper receiver group and Lo Profile gas block. The rest is entirely up to the customer and can be easily built out.

Barrel Specs:

  • Barrel Material: Chrome Moly Vanadium Steel
  • Made of Mil Spec M249 Machine Gun barrel steel, with heavy M249 Chrome Lining, (appx. 2 times as thick as an M4 or M16)
  • Barrel Type: Cold Hammer Forged
  • Barrel Caliber: 5.56mm NATO Barrel
  • Barrel Length: 14.5 Mid Gas, 16 Mid Gas, or 18 Rifle Gas
  • Barrel Profile: Modified Mid Weight Government Profile
  • Twist Rate: 1:7
  • Muzzle Thread: 1/2A~—28 TPI (Threads Per Inch)
  • Diameter At Gas Block: .750
  • Bore: Chrome Lined
  • Chamber: 5.56mm NATO


Does NOT come with a BCG, Muzzle device, Charging handle or handguard.

Component List:

  • Rainier Arms Mountain Mid Weight Series 1:7 Twist
  • Rainier Arms Match Lo Pro gas block
  • Rainier Arms Forged Mil-spec Upper Receiver with UPK
  • Rainier Arms Barrel nut
  • Gas tube
  • Weight: 18" - 2lbs 8.7 oz
  • Weight: 16" - 2lbs 6  oz
More Information
Manufacturer Rainier Arms, LLC
Finish No
Barrel Length No
Caliber No
Configuration No
Option AR15
Gas Length No
Height No
Rail Length No
Mount No
Profile No
Reticle No
Co Witness No
Size No