FailZero EXO Coated .223 Rem/5.56 NATO/300 BLK Complete Bolt Assembly

Manufactured by Fail Zero
SKU: FZ-Bolt-Assembly-01
Manufactured by Fail Zero
4 Reviews

Out of Stock

NOTE: Limit 5 per household. Quantities exceeding 5 will not allow checkout.



Not all Nickel Boron is created equal and FailZero is the undisputed pioneer of Nickel Boron technology. When failure is not an option, you can depend on FailZero.

Th .223 Rem/5.56 NATO/300 BLK Bolt Assembly is compatible with most MIL-SPEC AR-15/M4 carriers. All critical parts are coated with EXO Nickel Boron technology providing permanent dry lubricity, extreme durability and increased wear and corrosion resistance. This patented Nickel Boron coating will reduce friction and improve the overall performance of your rifle.

  • .223 Remington, 5.56 NATO, and 300 AAC Blackout compatible
  • Case hardened bolt
  • Shot peened
  • Magnetic particle inspected
  • MIL-SPEC components 
  • Nickel Boron treated parts include:
  • Bolt, extractor

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Bolt FinishNickel Boron
Bolt MaterialCarpenter 158 Steel
BrandFail Zero
Caliber Gauge5.56 NATO
Magnetic Particle InspectMagnetic Particle Inspected

WARNING: This Product can expose you to chemicals which is known to state of California to cause Cancer and Reproductive Harm. For more information, see

Ratings & Reviews

4 reviews

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Bought 4


I thought, and it proved correct, that this bolt matched with an Eis BCG, would give the best nag for the buck. Came out to a little over $200each and I am most pleased with the fit.The bolt, itself, was really tight and the extractor did not need a spring upgrade. I will wait until it has 500 rounds and then upgrade.Great stuff from a great company.

Replacement bolt


Primary arms shipping was very fast. I used this bolt to replace a damaged bolt in my suppressed rifle. So far it has worked 100% and operates more smoothly than the standard bolt.

Nice Bolt! Great Service


This bolt came with a perfect, even finish, and slightly radiused locking lugs. I am confident that this bolt will give me a long service life.

Fits well on my colt LE 6920


tried it on my colt LE 6920 and worked great. Kicked the shells in the same spot actually better than the colt stock bolt. Great product