Bolt Carrier Assembly, 5.56 NATO, Polished Nickel Boron

Bolt Carrier Assembly, 5.56 NATO, Polished Nickel Boron
Item Number: TR-BCA-PNIB
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Detailed Description


Manufactured by our finest domestic Mil-Spec contractors these are among the best 5.56 AR rifle bolts on the market and the same bolts we use as the basis of our renowned custom rifles!

Our bolt is precision machined from Carpenter No. 158 steel, shot peened for increased strength and a includes a tool steel extractor and ejector, appropriate extractor spring, and is MPI (Magnetic Particle Inspected and randomly batch HPT (High Pressure Tested). 
The extractor is 4140 gun quality, annealed, cold drawn steel per the Mil-Spec

The 8620 steel carrier includes a properly machined Mil-Spec gas key that is completely Nickel Boron plated for the ultimate in smooth operation and easy cleanup. It is secured to the carrier via Grade 8 fasteners and properly staked in our shop during final inspection.

These precisely machined, finished and hardened parts will ensure long term proper gas system functioning and reliability.

All experienced AR shooters know that the best spare parts kit for an AR-15 rifle is a spare complete bolt carrier assembly!

NOTE- The only difference between “semi-auto” and “full-auto” carriers are the carrier weight and external profile.  The “full-auto” carrier is slightly heavier to provide more mass and lower cyclic rate that can benefit carbine length and shorter gas systems, short barreled/suppressed rifles and machineguns. The “semi-auto” carrier is slightly lighter to provide the least amount of recoil impulse for rifle length gas systems and its design makes reinstalling the firing pin easier after cleaning.

Both carrier types are considered completely interchangeable and there are no restrictions on the ownership of a “full auto” carrier group in a semi-automatic rifle.

  • Nickel Boron Plated for easy cleanup and less lubrication
  • Mil-spec parts ensure a long service life
  • Machined ejector and extractor per mil specs
  • Full Auto carrier (see note)
  • Drop in fit for any quality 5.56 case head based AR rifle (.223/5.56 NATO, .300 Blackout, .204 Ruger, 300 HAM’R or 7.62X40 WT)

Why Nickel Boron is a Superior Choice for AR Bolt Carrier Groups

  • Outperforms hard chrome and nickel-phosphorous (hardness/wear resistance)
  • Withstands high temperatures and is easy to clean
  • High hardness (Rockwell 70 C +)
  • Greater abrasion and wear resistance over time
  • Low coefficient of friction requires less lubrication
  • No hydrogen embrittlement