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AR-15/M16/M4 Full Auto Bolt Carrier Group – NiB-X Nickel Boron POLISHED

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A nickel boron coating imparts hardness, lubricity and protection against corrosion — where better to put it than the heart of your AR-15? This polished nickel BCG is treated with WMD Guns’ proprietary NiB-X® coating to give it a surface 40% harder than chrome and virtually impervious to fouling. 

Every piece of this assembly is produced to military specifications and subjected to top-tier testing and metal treatment protocols to deliver a premium component that fits the AR-15, M16 and M4. The full auto design provides additional weight to support reliable cycling when used in a semi-automatic firearm.


Nickel Boron Full-Auto Bolt Group for the AR-15/M16/M4

WMD Guns is an industry leader in creating and applying firearm coatings, and this polished nickel boron bolt group is one of our top examples. We treat every critical surface with our proprietary NiB-X® finish for a glossy silver bolt group that looks as impressive as it performs. 

And since this assembly comes from WMD, you know that every piece underneath that performance coating is made using top-grade materials and meets exacting military specifications. If you need a bolt group made for extreme reliability in a suppressed build, SBR or other high-performance setup, our full-auto units will deliver. 

The Advantages of a Nickel Boron Bolt Carrier Group

The AR-15’s direct gas impingement system requires a lot of moving parts. Specifically, the bolt carrier group (BCG) — comprising the bolt, extractor, ejector, cam pin, firing pin, gas key and carrier — must move back and forth under pressure from either gas or the buffer spring to complete firing operations. Since every cycle exposes this assembly to carbon-laden gas, your BCG has the potential to accumulate a lot of carbon buildup.

On an untreated carbon steel BCG, that buildup worsens with continued shooting, slowing reciprocation and eventually resulting in cycling issues. Removing that carbon to restore your AR’s function often requires aggressive scrubbing and heavy solvent application. 

With a nickel boron coating for your bolt group, that difficulty is virtually eliminated. Nickel boron offers a high degree of lubricity, meaning your BCG will continue to cycle reliably long after uncoated models have bound up. Better yet, that same lubricity keeps carbon from sticking to your BCG’s surfaces. When it’s time to clean your AR-15, a high-polish nickel BCG simply wipes clean — no solvents, wire brushes or elbow grease required. 

What Does It Mean for a BCG to Be Full Auto?

A full-auto M16 bolt group will not make an AR-15 fully automatic on its own — accomplishing that requires a few other parts, some paperwork and a chunk of money. 

Semi- and full-auto BCGs differ in the design of their back end, with the latter having extra material that enables a fully automatic trigger to function as intended. This rear lug adds a slight mass increase to the assembly.

Though the weightier back end is necessary to make a full-auto trigger work, it will not inhibit the function of a firearm built solely for semi-automatic operation. In fact, many shooters purposefully choose a full-auto BCG for their AR-15s because the extra mass helps with cycle timing, reduces wear and tear, and lowers recoil on lighter builds.

Order Full-Auto Nickel Bolt Carrier Groups Online

WMD Guns’ polished nickel 5.56 BCGs combine an industry-best coating with premium parts and manufacturing from Defense Industrial Base suppliers. Every essential component is treated with NiB-X® to give you performance that easily survived a 30,000-round government endurance test without wearing, chipping or flaking. 

This .223/5.56 BCG’s specifications are as follows:

  • Bolt: Case-hardened 9310 steel with Mil-Spec NiB-X® extractor, gas rings and ejector, plus specialized O-ring buffer. Shot peened and magnetic particle inspected for quality assurance.
  • Firing pin: Produced to government specifications, hardened, heat-treated and chromed.
  • Carrier: 8620 material with full-auto design for function in M16s, M4s and AR-15s. Produced, case-hardened and coated under stringent quality control protocols. 
  • Gas key: Hardened per USGI specs and secured with grade 8 fasteners, Permatex Sealing Compound and military-recommended staking procedure.
  • Cam pin: Manufactured and hardened per government drawings, then coated with NiB-X® for smooth function.

Buying a full-auto nickel BCG requires no special paperwork, and our NiB-X® coating is guaranteed for life. Order online today to give your AR-15 the upgrade it deserves, or reach out to our team to learn more about our products or coatings.



.223/5.56, .224 Valkyrie, 450BM, .458 SOCOM, 6.5 Grendel Type II, 6.8 SPC, 7.62x39mm

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