Component AnalysisReliabilityQC Critical

Advanced Coatings & BCG Guide

Not all shiny coatings are created equal. We break down the metallurgy and hype behind Diamond-Like Carbon (DLC), Nitride, Nickel Boron, Hard Chrome, and classic Phosphate. Understand why some "upgrades" might actually reduce your reliability, and which coatings are worth the premium price tag for a smoother, easier-to-clean rifle.

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Before You Read

This guide assumes familiarity with these topics:

How to Build Your First AR-15->AR-15 Lower Parts Quality->

The Contenders: Coating Profiles

Detailed analysis of the most common finishes on the market today.

Hard Chrome

Process: Electrolytic PlatingVerdict: Premium

The original choice for the M16. Chrome is making a huge comeback because it is incredibly easy to clean, forgiving of neglect, and has a proven 50+ year track record. It is arguably the most practical finish for a duty rifle.

Pros

• Easiest to clean (carbon wipes off effortlessly).
• Extremely durable bond to the steel.
• High natural lubricity.
• Bright finish makes inspecting for fouling easy.
• Impervious to rust if done correctly.

Cons

• Can have hydrogen embrittlement if not properly stress-relieved (rare in modern quality parts).
• Flashier (silver) than black coatings.

Hardness

Very High (65-70 HRC)

Lubricity

High

Best For

Duty rifles, suppressed builds, and anyone who wants maximum reliability with minimal maintenance.

DLC (Diamond-Like Carbon)

Process: PVD (Physical Vapor Deposition) / PACVDVerdict: Premium

$$$

The gold standard for modern BCGs. DLC is an incredibly hard, thin coating that provides extreme scratch resistance and natural lubricity without adding meaningful thickness.

Pros

• Extremely hard and virtually scratch-proof.
• Very low coefficient of friction (slick).
• Chemical and corrosion resistant.
• Doesn't flake or chip like NiB can.
• Thin application preserves dimensional tolerances.

Cons

• Expensive compared to Nitride.
• Requires proper surface prep for best adhesion.

Hardness

Extreme (90+ HRC)

Lubricity

Exceptional (0.1 CoF)

Best For

High-end duty builds, suppressed rifles, and users who hate cleaning.

Black Nitride (QPQ / Melonite)

Process: Thermochemical Case HardeningVerdict: Standard

The best value for money. Nitride is a surface treatment, not a coating, meaning it won't chip or flake. It case-hardens the steel and adds corrosion resistance.

Pros

• Zero dimensional change (it treats the metal itself).
• Extremely durable and corrosion resistant.
• Cost-effective.
• Slicker than phosphate.

Cons

• Not as slick as DLC or NiB.
• Can result in brittle parts if heat treat is done poorly (avoid cheap brands).

Hardness

High (60-70 HRC)

Lubricity

Good

Best For

General purpose builds, budget-conscious duty rifles, and high-volume training.

Nickel Boron (NiB)

Process: Electroless PlatingVerdict: Avoid

Once the top upgrade, NiB has fallen out of favor due to quality control issues. While very slick initially, it can flake, tarnish, and cause tolerance stacking issues.

Pros

• Extremely slick to the touch.
• Easy to identify fouling (silver color).
• High initial lubricity.

Cons

• Prone to flaking and shipping over time.
• Can cause hydrogen embrittlement in the steel.
• Added thickness can cause tight tolerance issues.
• Stains and tarnishes permanently with use.

Hardness

High (70+ HRC)

Lubricity

Very High

Best For

Those who prioritize initial slickness over long-term reliability (Not Recommended).

Phosphate (Mil-Spec)

Process: Conversion CoatingVerdict: Legacy

The military standard. It absorbs oil like a sponge, keeping the BCG lubricated even when dirty. Ideally paired with a Chrome-lined bore and gas key.

Pros

• Holds oil exceptionally well (porous).
• Standard and proven for decades.
• Cheap and readily available.

Cons

• High friction if run dry.
• Hardest to clean (fouling sticks).
• Technically less advanced than Nitride/DLC.

Hardness

Standard

Lubricity

Low (Requires Oil)

Best For

Clone builds, strict mil-spec requirements, and 'if it ain't broke' purists.

Titanium Nitride (TiN)

Process: PVDVerdict: Standard

$$$

Recognizable by its gold color. TiN is hard and slick but often chosen for aesthetics. It is a PVD coating but typically softer than DLC.

Pros

• Very hard and wear resistant.
• Good lubricity and corrosion resistance.
• Distinctive gold aesthetic.

Cons

• Costly.
• Can be flashy for duty use.
• Not as hard as DLC.

Hardness

High (80+ HRC)

Lubricity

Good

Best For

Competition guns and showpiece builds.

Head-to-Head Comparison

Quick reference for how these finishes stack up in key performance areas.

Hardness (Wear Resistance)

DLC

DLC offers the highest surface hardness, resisting scratches and wear better than any other option.

Lubricity (Slickness)

DLC / NiB

NiB feels slickest to the touch, but DLC offers comparable low friction without the risk of flaking.

Corrosion Resistance

Nitride / DLC

Both offer exceptional protection against rust and elements.

Ease of Cleaning

Chrome / DLC

Carbon wipes right off Chrome and DLC. Phosphate requires scrubbing.

Value

Nitride

Nitride offers 90% of the performance of DLC for 50% of the price.

The "Just as Good" Trap

Avoid unbranded "Nitrided" BCGs from budget bin websites. Nitriding is a precise heat treatment. If done poorly, it makes the steel brittle, leading to bolt lugs snapping off at low round counts.

Rule of thumb: Only buy Nitride or DLC BCGs from reputable manufacturers (Toolcraft, Microbest, BCM, Sons of Liberty, etc.) who use Carpenter 158 or 9310 steel with proper heat treat protocols.

Trusted BCGs by Coating Type

Don't gamble on no-name parts. These are verified reliable options for each coating type.

Reviewer's Choice (DLC)

Toolcraft DLC 5.56 BCG

The gold standard for value and performance. Toolcraft is an OEM for many top brands. Their DLC coating is extremely slick and durable.

✓Carpenter 158 Bolt
✓Extreme hardness
✓Easy cleaning

Verified Retailer

Check Price at OpticsPlanet

Duty Grade (DLC)

BCM Bolt Carrier Group (IonBond/DLC)

BCM's legendary QC applied to a DLC (IonBond) finish. If you need a bolt that will run forever suppressed, this is it.

✓HP/MPI Tested
✓Properly staked gas key
✓Industry leader

Verified Retailer

Check Price at OpticsPlanet

The New Standard (Chrome)

Microbest Hard Chrome BCG

Microbest is the OEM for many premium brands. Their full-chrome BCGs are arguably the most durable, easy-to-clean option on the market today.

✓Extreme durability
✓Wipes clean instantly
✓Mil-spec reliability

Verified Retailer

Check Price at OpticsPlanet

Premium Pick (NP3)

SIONICS NP3 BCG

If you can find one, buy it. NP3 is widely considered the slickest, most durable coating available, surpassing even NiB in longevity.

✓Unmatched lubricity
✓Impervious to corrosion
✓Rare but worth it

Verified Retailer

Check Price at OpticsPlanet

Legacy Pick (NiB)

FailZero Nickel Boron BCG

While we generally recommend DLC over NiB now, FailZero is the original and most reputable source if you must have the silver look.

✓EXO Nickel Boron technology
✓High initial slickness

Verified Retailer

Check Price at OpticsPlanet

Next Step

Ready to continue? Here's the recommended next guide:

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AR-15 Brand Comparison 2025->

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