Rainier Arms Precision Match Grade BCG - Nickel Boron


The Rainier Arms Precision Match Grade Nickel Boron BCG - 5.56 is machined and finished to a higher standard to meet and exceed all Mil Spec. It is machined using the most precise equipment in the industry. The bolts are MPI tested & Marked to give you ultimate confidence in your weapon system.


  • Full Auto Carrier
  • SAE 8620
  • Heat Treated
  • Nickel Boron Plated



  • 5.56/.223
  • Carpenter A-158
  • Shot Peened
  • Heat Treated
  • Nickel Boron Plated



  • Machined from bar
  • Shot Peened
  • Heat Treated
  • Nickel Boron Plated


Extractor Spring:

  • Chrome Silicone for Longer Life
  • Black Insert as per current Mil-Spec
  • "O" Ring is high temp resistant dark brown


Extractor Retaining Pin:

  • Precision Machined
  • Precision ground to diameter
  • Precision ground to length
  • Heat Treated


Firing Pin:

  • Machined and then precision ground for accuracy
  • Heat Treated


Gas Key Bolt:

  • Precision manufactured in house with extra deep knurling
  • Grade 8
  • 1200 degree locking patch is factory applied to threads to help insure long lasting tightness


Gas key:

  • Hard Chrome lined gas tube as per Mil-Spec
  • Bolts installed to proper torque
  • Staking on both sides of both bolts


Cam Pin:

  • Precision machined
  • Heat Treated
  • Nickel Boron Plated


Firing Pin Retaining Pin:

  • Precision bent
  • Precision cut to length
  • Heat Treated


Gas Rings:

  • Stainless Steel per Mil-Spec



  • Precision machined
  • Heat Treated


Ejector Spring:

  • Chrome Silicone
  • Precision ground ends


Ejector Retaining Pin:

  • Precision cut to length
  • Hard Chrome Plated



Limited Lifetime Warranty
We are so confident in our Rainier Arms NiB BCG we offer them with a limited lifetime warranty. So if at anytime your Rainier Arms NiB BCG breaks on your during normal use(Intentional abuse & Gas Key wear not included) we will replace it.

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