Fail Zero EXO Nickel Boron 5.56/.223 Bolt Assembly

The Fail Zero EXO Bolt Assembly (brand part number EXO-BOLTASSEMBLY01) is a fully assembled 5.56/.223 bolt built to fit most mil-spec AR15, M16, and M4 carriers, and it is finished in Fail Zero’s EXO Nickel Boron coating for anyone replacing just the bolt rather than a full carrier group. The nickel boron finish gives the bolt a permanently lubricious surface that keeps it running smoothly and sheds carbon fouling far more easily than a bare phosphate bolt. Reduced friction from the coating also translates into a small but real bump in reliability and felt performance. It is a direct swap for builders standardizing on Fail Zero’s coated internals.

Key Specifications

• 5.56/.223 chambering matches standard AR15/M16/M4 bolt specifications.
• Fits most mil-spec AR15, M16, and M4 carriers for broad compatibility.
• Fully assembled bolt ready to install without additional fitting.
• EXO Nickel Boron coating for a permanently lubricious surface.
• Reduced friction for easier cleanup and smoother cycling.

Frequently Asked Questions

What carriers does this bolt fit? Most mil-spec AR15, M16, and M4 carriers chambered in 5.56/.223.

Why choose a nickel boron-coated bolt? The coating reduces friction, sheds fouling faster, and improves both cleanup and cycling reliability.

Buy the Fail Zero EXO 5.56/.223 Bolt Assembly

Upgrade just the bolt with a coated part built to run smoother and clean up faster. Order it from our Lubbock, Texas gun shop as soon as it’s available to ship, and browse more AR15 bolts for your build.