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Rainier Arms Mountain - Stripped Upper Receiver Group CHF Barrel

Out of stock

Rainier Arms Mountain - Stripped Upper Receiver Group CHF Barrel

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
Option AR15