Understanding Metals, Finishes, and Coatings on the AR

When building or selecting an AR-15, understanding the materials and finishes of its components is crucial. The choice of metals for each component directly impacts the weapon’s strength, weight, and durability. Equally important are the surface treatments and coatings applied to these metals. Finishes like hardcoat anodizing, phosphate coatings, and Cerakote not only enhance corrosion resistance but also affect the firearm’s longevity and maintenance requirements.

This guide delves into the various metals used in AR-15 construction and the finishes that protect them, providing insights to help you make informed decisions for a reliable and enduring build.

Base Metals

Aluminum

Aluminum alloys are very important in the AR platform. The light weight, machinability, and affordability of aluminum make it the primary metal for larger metal components, like the lower receiver, upper receiver, handguard, and receiver extension.

Aluminum alloys come in different compositions and tempering. The most important of these is 7075 T6. This alloy is used as the primary material for receivers, receiver extensions (except commercial spec; see our What the Spec article for more information), and some lightweight bolt carriers. Any of these components forged or milled from 6061 aluminum should be avoided; 7075 is denser, stronger, stiffer, and harder than 6061, which is needed in these important components.

Less critical components use a variety of alloys, including 6061. This is not a bad thing; as long as it is not one of the components listed above, the alloy used is not as important.

Aluminum can be found in the following AR components:

Lower Receiver
Upper Receiver
Free Float Handguard
Dust Cover
Charging Handle
Receiver Extension
Lightweight Bolt Carrier
Lightweight Pivot/Takedown Pins

Alloy Steel

Alloy steel is one of the most important metals in your AR. It’s hardness, stiffness, and durability makes it the default for many high-pressure, high-impact, and high-friction components.

Steel is an alloy of iron and carbon. Alloy steel is steel alloyed with a variety of other elements, typically comprising between 1% and 50% by weight.

The elements used will influence the physical and chemical properties of the alloy, including machinability, hardness, corrosion resistance, and strength.

The alloy elements used will vary by the designation. The following alloys are commonly used in the AR platform:

41xx (e.g. 4130, 4140, 4150): barrel, gas key, gas key screws, extractor
43xx (e.g. 4130): cam pin, extractor
86xx (e.g. 8620): bolt carrier
93xx (e.g. 9310): bolt*
C158: bolt*

* Be wary of bolts that are not made from 9310 or C158 steel. 4140 is an inferior alloy in this application. The hardness of 9310 steel is between 58 and 62 HRc; the hardness of 4140 is 28 to 32 HRc. The decreased hardness is not a good thing for the high-stress and high-pressure environment of the bolt. And if the difference in physical attributes are not convincing enough, a 4140 bolt DOES NOT MEET MIL-SPEC STANDARDS.

Alloy steel can be found in the following AR components:

Bolt Carrier
Bolt Barrel
Muzzle Device
Crush Washer/Timing Shims
Gas Block
Dust Cover
Forward Assist
Pivot/Takedown Pins
Magazine Catch
Bolt Catch
Trigger Group
Safety Selector
End Plate
Castle Nut
Screws/Bolts Springs
Detents

Stainless Steel

Stainless steel is a metal that is designed for corrosion resistance. It has a higher percentage of chromium than other alloy steel, which forms a chromium oxide layer on the outer surface, which inhibits corrosion and rust.

While stainless steel can be used in place of other alloy steel in many springs, pins, and bolts, it’s most conspicuous use is in barrels. There are generally two types of stainless steel used in barrels. 416 and 416R. 416R is superior to 416 due to reduced sulfur and increased molybdenum content. This difference in composition makes 416R harder than 416, and thus, more resistant to corrosion and wear.

Stainless steel can be found in the following AR components:

Barrel
Muzzle Device
Gas Block
Gas Tube
Firing Pin
Pivot/Takedown Pins
Screws/Bolts
Springs
Detents

Titanium

Titanium is known as one of the strongest metals per unit of weight. It’s alloys are lighter than steel and is harder and stronger than both steel and aluminum alloys. That said, this metal is also less rigid and more brittle than steel, so it must be used thoughtfully. Used appropriately in place of steel and aluminum, titanium alloy can shed weight from an AR build.

Titanium can be found in the following AR components:

Lightweight Bolt Carrier
Lightweight Pivot/Takedown Pins
Screws/Bolts

Metal Properties

*: If properly heat treated.

Based on density.
Based on Brinell hardness.
Based on Modulus of Elasticity (a.k.a. Young’s Modulus).
Based on Yield Strength.
Pre-failure ductility based on the normalized difference between Ultimate Strength and Yield Strength.
Based on Ultimate Tensile Strength.
Based on Charpy Impact Test.
Based on Shear Modulus.

Typical Use of Metals and Other Materials in the AR Platform

Component	Steel	Aluminum	Titanium	Plastic and Rubber
Lower Receiver		X
Upper Receiver		X
Handguard	Screws	Free Float		Drop-In
Muzzle Device	X
Crush Washer or Timing Shims	X
Barrel	X
Gas Block	X
Gas Tube	X
Bolt Carrier Assembly	X	Lightweight	Lightweight
Bolt	X
Firing Pin	X		X
Dust Cover	X	X	X	X
Forward Assist	X	Cup	Cup
Charging Handle	Springs	X
Pivot and Takedown Pins	X	X	X
P/TD Pin Detent	X
P/TD Pin Spring	X
Magazine Catch	X
Magazine Catch Spring	X
Magazine Release Button		X
Bolt Catch	X
Bolt Catch Buffer	X
Bolt Catch Spring	X
Trigger Group	X
Safety Selector Switch	1 Piece 2 or 3 Piece (Barrel)	2 or 3 Piece (Lever)
Safety Selector Detent	X
Safety Selector Spring	X
Pistol Grip				X
Pistol Grip Bolt/Screw	X
Pistol Grip Lock Washer	X
Buffer Retainer Pin	X
Buffer Retainer Spring	X
Receiver Extension		X
End Plate	X
Castle Nut	X
Buffer	Weights¹	Body		Bumper
Buffer Spring	X
Buttstock	Springs			X

1: Heavy buffers may use tungsten weights in place of or in addition to steel. Light weight buffers may use aluminum weights in place of steel.

Finishes and Coatings

Finish-Substrate Compatibility

The table below indicates the compatibility between substrate (metal, plastic, rubber) and the various finish/coating options in the AR platform:

Finish/Coating	Steel	Aluminum	Plastic/Rubber
Anodized Type III	—	X	—
Black Oxide	X	—	—
Manganese Phosphate	X	—	—
Salt Bath Nitride	X	—	—
Hard Chrome	X	X	—
Nickel Boron (NiB)	X	X	X
Titanium Nitride (TiN)	X	X	—
Diamond-Like Carbon (DLC)	X	X	—
Water Transfer	X	X	X
Spray Paint	X	X	X
DuraCoat	X	X	X
Gunkote	X	X	X
Cerakote	X	X	X

Metal Finishes in the AR

The table below summarizes the physical characteristics of common metal finishes available in the AR platform:

Finish	Metal	Unfinished Hardness	Finished Hardness	Lubricity¹
Anodized Type III	Aluminum	150 HB	380-520 HB / 41-54 HRc	–
Hot Black Oxide	Steel	197 HB / 15 HRc (4140)	no significant change	–
Cold Bluing	Steel	197 HB / 15 HRc (4140)	no significant change	–
Manganese Phosphate	Steel	197 HB / 15 HRc (4140)	390-430 HB / 42-46 HRc	+
Nitride	Steel	197 HB / 15 HRc (4140)	530-770 HB / 55-70 HRc	++
Hard Chrome	Steel	197 HB / 15 HRc (4140)	745-800 HB / 68-72 HRc	++
Nickel Boron	Steel	197 HB / 15 HRc (4140)	>770 HB / 70-80HRc	+++
Titanium Nitride	Steel	197 HB / 15 HRc (4140)	>800 HB / 80-85 HRc	++++
Diamond-Like Carbon	Steel	197 HB / 15 HRc (4140)	>800 HB / 85-90 HRc	+++++

1: Lubricity for a solid is basically the implied surface slickness, and does not have a direct scientific measurement. This attribute is most relevant for bolt carrier groups, as they must slide over the interior surface of the upper receiver with each cycle. The results here are based on our tactile observations and your experience and opinion may differ. The principle of lubricity/slickness is component of a larger field of material science/engineering called tribology, which which is the study of the interaction of two materials with consideration to friction, wear, and lubrication. Lubricity/slickness can be inferred via the coefficient of friction (CoF), which reflects the force required to move two objects of specific materials or finishes over one another, whether dry or lubricated. Unfortunately, we are unaware of any comprehensive, objective, and consistent study of finishes that can be used to identify the best performing finish for a bolt carrier. Manufacturer’s are happy to provide data for their own finishes, but they are likely to be biased (i.e. cherry-picked) and based on inconsistent conditions (i.e. with the best case conditions for a particular finish, however impractical). There is a need for an absolute (not relative) scientific study of BCG finishes and the testing conditions must be controlled (e.g. calibrated instruments, consistent procedure/test method, consistent conditions), practical (e.g. not at super-cooled temperatures or using lubricants not available on planet Earth), consistent across all finishes tested, and under both dry and lubricated (using the same lubricant) conditions. If we can find an official laboratory to do a CoF study on BCG finishes (i.e. according to ASTM G115), we will happily loan BCGs with varying finishes for non-destructive testing. If the study cannot be done on BCGs (i.e. the test requires a coated coupon/plate/ball/pin of a specific size), we would be happy to solicit/broker finish samples from various manufacturers. In the meantime, we will work on a scientific test that we can perform, though it will measure relative performance and will not be according to any ASTM standard by any stretch of the imagination. Once we develop and execute our at-home study, we will publish the procedure and results.

Anodized

Anodizing is an electro-chemical oxidation process that results in an unnaturally thick oxidation layer on the surface of a metal, most commonly aluminum. Anodizing is typically performed to improve the resistance to wear and corrosion by increasing the surface hardness of the metal.

Anodizing is performed by running an electric current through an electrolytic acid solution and through the object itself. Metal ions (for aluminum, this is Al3⁺) pass from the object into the electrolyte solution (the acid), while superoxide (O2^–) ions simultaneously diffuse into the metal. The resulting thick oxide layer is significantly harder and more stable than the unoxidized metal and the natural oxide layer.

Type III anodizing, or hardcoat anodizing, is based on the military standard Mil-A-8625. This level of anodization results in an oxide layer that is up to 75,000 times thicker than the natural oxide layer. Type III anodizing is very important to structural components of an AR, as well as any components that will experience significant amounts of stress or abrasion. Type III anodizing should be used as the minimum acceptable surface finish for the following aluminum components:

Lower Receiver
Upper Receiver
Handguard (except plastic drop in)
Receiver Extension
Lightweight Aluminum Bolt Carrier

Oxide

Blackening of firearm components is typically either done by a hot process (hot black oxide) or a cold process (cold bluing).

Hot Black Oxide

Black oxide, or blackening, is a chemical conversion of iron into a black oxide called magnetite (Fe3O4). While a type of iron oxide, magnetite is not rust (Fe2O3), a red oxide. By proactively oxidizing the iron to black oxide, you can preempt the formation of red oxide.

In this process hot baths of sodium hydroxide, nitrates, and/or nitrites are used to convert the surface steel to magnetite.

The resulting finish imparts mild corrosion resistance and decreases the shine of the metal. It can be found as a finish on barrels (though uncommon in the AR platform) and crush washers.

Cold Black Oxide (a.k.a. cold bluing)

Cold black oxide is not actually an oxide conversion finish, like hot black oxide. This finish consists of copper selenide deposited on the surface of the steel. This finish imparts very little change to the physical properties of the steel. This finish is rarely seen on the AR platform.

Manganese Phosphate

Known as phosphate, manganese (or zinc, depending on the chemical process) phosphate, phosphatized, or Parkerized, this is the Mil-Spec (and therefore, the default) coating for many steel components in the AR platform.

The phosphate coating is a chemical conversion coating that is the result of soaking a steel part in a bath of phosphoric acid with soluble zinc (zinc phosphate) or manganese (manganese phosphate) salts. The resulting finish is a hard, matte black coating precipitated onto the surface of the steel. The finish also improves the acceptance of lubricants vs. uncoated steel, which is useful for the moving parts of the AR platform.

Phosphate coated steel can be found in many components of the AR platform, including:

Muzzle Device
Crush Washer
Barrel
Gas Block
Bolt Carrier Group
Dust Cover
Forward Assist
Pivot/Takedown Pins
Magazine Catch
Bolt Catch
Bolt Catch Buffer
Trigger, Hammer, and Disconnector
Hammer/Trigger Pins
Trigger Guard
Safety Selector Switch
Buffer Retainer Pin
Receiver Extension End Plate
Receiver Extension Castle Nut

Nitride (FNC)

Known as nitride, ferritic nitrocarburizing (FNC), Melonite, Tenifer, Tifftride, quench-polish-quench (QPQ), and salt bath nitride, this is a common upgraded finish for steel components on the AR platform.

Nitride finish is the result of infusing nitrogen into the surface of a metal, creating a case-hardened surface. The nitriding surface involves dipping steel into a bath of hot nitrogen salts. The resulting finish is very hard, and has good resistance to corrosion and wear.

Many steel parts in the AR platform can be nitrided for improved resistance to wear and corrosion, including:

Muzzle Device
Barrel
Gas Block
Gas Tube
Bolt Carrier Group*
Pivot/Takedown Pins
Magazine Catch
Bolt Catch
Safety Selector Switch
Buffer Retainer Pin

*Note that we do not recommend nitride bolts. Check out our Don’t Buy a Nitride Bolt article for to understand why.

Hard Chrome

Chrome plating is an electro- or chemically-plated finish applied to the exterior of a metal.

Chrome plating is typically applied by electroplating chromium onto the surface of a metal.

A chrome finish is very hard, and is resistant to heat, corrosion, and wear. It also imparts reduced friction. Because of these characteristics, it is the Mil-Spec finish for certain component surfaces, like barrel bore, bolt carrier lining, and gas key lining.

Chrome plating may be found on the following AR components:

Barrel (hard chrome lining)
Gas key (hard chrome lining)
Bolt Carrier (hard chrome lining)
Bolt Carrier Group (hard chrome exterior)
Various Small Parts (cosmetic chrome)

Nickel Boron (NiB)

Nickel boron, also known as NiB and electroless nickel-boron plating, is a metal plating of a nickel-boron alloy applied to a substrate.

Unlike chrome plating, NiB coating does not require electrical current. The application of NiB involves dipping an object into a bath containing nickel salt and a boron-containing reducing agent (e.g. sodium borohydride).

NiB is significantly harder than unfinished steel, on the order of (or in excess of) hard chrome. NiB coating results in a columnar structure of nickel and boron that results in microscopic nodules on the surface of the object. These nodules reduce the surface-to-surface contact between two mating surfaces and, thus, decrease friction, improve heat dissipation, and increase lubricant-carrying capacity. These characteristics make nickel boron a good candidate for bolt carrier finish, which is where you will typically find it on an AR.

Titanium Nitride (TiN)

Titanium nitride, also known as TiN and Tinite, is an extremely hard ceramic material that can be applied to various metals. TiN is typically applied via physical vapor deposition. This method involves evaporation/sublimation of a solid (in this case, the TiN) in a vacuum and subsequent condensation/deposition as a thin film on a substrate.

TiN is extremely hard and has a low coefficient of friction. These characteristics make TiN a good coating for bolt carrier groups.

Visually, TiN is typically anywhere between a lustrous gold finish to a satin orange-yellow finish. If you don’t mind a little flash, this can look pretty cool peaking out of the ejection port.

Diamond-Like Carbon (DLC)

Diamond-Like Carbon, or DLC, is a state of the art finish that, as the name implied, is extraordinarily hard.

As with TiN, DLC is applied via physical vapor deposition. This method involves evaporation/sublimation of a solid (the sp3 hybridized carbon atoms) in a vacuum and condensation/deposition as a thin film on a substrate.

DLC is the hardest finish as you will find on the AR platform and it is extremely durable. It has superior lubricity compared to every other finish (even running dry). If you have the money to spend, you can’t go wrong with a DLC-coated bolt carrier.

Metal Coatings in the AR

The table below summarizes the physical characteristics of common firearm coatings:

Coating	Hardness	Corrosion Resistance¹	Chemical Resistance	Abrasion Resistance (Cycles/Mil)	Adhesion	Impact Resistance
Hydro Dip	–	–	–	–	–	–
Spray Paint	–	–	–	–	–	–
DuraCoat	+	++²	results not available	++³	+++	+++
KG Gun Kote	+++⁴	+^3,4	++^3,4	++^3,4	results not available	results not available
Cerakote	+++	+++	+++	+++	+++	+++

Cerakote has sponsored head-to-head laboratory testing on various competitor finishes and coatings. The results can be found HERE. Of particular interest is there head-to-head corrosion resistance testing, which can literally be witnessed HERE.
Due to lack of transparency and broken links to test results, we discount the results published by DuraCoat. The value presented in the table is based on a comparative laboratory study sponsored by Cerakote.
Results from manufacturer not available. Results in table based on comparative laboratory study sponsored by Cerakote.
KG has not published the results of testing performed on Gun Kote (other than hardness, which they report as 9H pencil hardness, just like Cerakote). We have reached out to them requesting the test results, but we have not received any reply. Values provided in this table are based on testing performed on KG Gun Kote as a comparator by Cerakote. If KG provides their test results, we will update this table, accordingly.

Hydro Dipping

Hydro dipping, also known as water transfer printing, allows the application of printed designs to three dimensional surfaces. This finish can be used to apply patterns and graphics to AR components.

This finish typically begins by first printing a pattern on a hydrographic film. The film dissolves in water, so, when it is placed on the surface of a water bath, the film dissolves, leaving the printed image floating on the surface of the water. When an object is pushed through this layer, the ink adheres to the surface of the object. The applied graphics require a clear coat for protection.

The technique may also involve spraying paint on the surface of a water bath, and otherwise following the process for printed patterns. The applied paint requires a clear coat for protection.

This finish is purely cosmetic and because the patterns are printed, the effects can be pretty sweet. However, this finish imparts zero structural value. It is prone to scratching, chipping, etc., which can make your gun look like sh*t pretty quickly if you don’t protect it.

Spray Paint

We don’t need to explain this one. Spray paint is an easy way to change the look of your gun. It can be applied free hand or in patterns using stencils or foliage to impart shapes and designs.

Spray painted parts should have clear coat applied to protect the finish.

As with hydro dipping, this is purely cosmetic and is susceptible to wear, scratching, etc. without the appropriate protective top coat.

DuraCoat

DuraCoat is like spray paint on steroids. The proprietary blend formulation offers a robust finish that can easily be applied by the average Joe and does not require specialized equipment, significant surface preparation, baking, etc.

DuraCoat is offered in over 300 colors, with various additives for texture and appearance. It is offered as a liquid for use with spraying equipment, or in aerosol cans for the DIY-er.

Because DuraCoat is offered in convenient spray cans, it is as easy to apply as normal spray paint. Unlike hydro dipping and spray painting, DuraCoat finishes do not require any clear coat and the finish is much more resilient. So, if you are thinking about hydro dipping or spray painting your gun, we strongly recommend that you consider using DuraCoat instead; for a comparable level of effort, you will get longer-lasting results.

While leaps and bounds better than hydro dip and spray paint, DuraCoat is less durable than baked on finishes, like KG Gun Kote and Cerakote.

KG Gun Kote

KG Gun Kote is a baked on finish that is relatively easy to apply to any substrate.

KG Gun Kote is offered in nearly 100 colors/finishes. It is offered as a liquid for using with spraying equipment.

Given the need for application equipment and baking equipment, you could consider KG Gun Kote to be a bit less DIY-friendly than DuraCoat, but more DIY-friendly than Carakote.

KG Gun Kote is generally more robust than DuraCoat, but cannot compete with attributes of Cerakote.

Cerakote

Cerakote is a baked on ceramic-polymer coating that can be applied to metals and plastic.

The physical characteristics of Cerakote are superior to all other firearm coatings. It is harder, more corrosion resistant, abrasion resistant, and chemical resistant, and has the best rating for adhesion.

Cerakote is offered in hundreds of colors and comes in a slurry/suspension.

For all of the benefits of Cerakote, it is NOT DIY-friendly. Unless you are adventurous and don’t mind effing up hundreds of dollars worth of components, you will probably need to find a competent/authorized applicator who has the knowledge/experience, as well as the equipment to apply this coating properly. Or just buy components that are already coated.

Frequently Asked Questions

What is the best finish for an AR-15 bolt carrier group (BCG)?

The top finishes for BCGs each have strengths:

Hard chrome: Military-proven, very heat-resistant
Nickel boron: Smooth cycling and easy to clean, but can wear under heat
Nitride (FNC): Great corrosion resistance, but may temper core hardness of critical components (like the bolt) and softens at high temps (check out our Don’t Buy a Nitride Bolt article)
DLC (diamond-like carbon): Ultra-hard, low-friction, thermally stable, and resistant to wear and corrosion. DLC doesn’t alter heat treatment and is ideal for high-end builds. DLC is increasingly favored for premium BCGs due to its excellent wear resistance and no drawbacks related to thermal degradation or tempering.

Nitride vs phosphate in the AR-15: Which is better?

Phosphate (parkerized) is rugged, oil-retentive, and field-tested.

Nitride (via FNC) penetrates the steel and is significantly harder than phosphate, but the high processing temperatures (~1000°F) can temper hardened steel, reducing core hardness and fatigue strength. Chrome and DLC, by contrast, are low-temperature coatings, preserving core metallurgy and offering better surface performance than either phosphate or nitride.

Is a chrome-lined barrel better than a nitride barrel?

Chrome-lined barrels resist erosion and heat well, ideal for full-auto or harsh use.

Nitride barrels may offer better accuracy and smoother bores initially, but the process can soften the steel’s core slightly, and the surface layer loses hardness as temperatures climb. For full-auto or sustained fire, chrome is often superior.

What is salt bath nitriding on AR parts?

Salt bath nitriding, or ferritic nitrocarburizing (FNC), diffuses nitrogen and carbon into the surface of steel to improve hardness, wear resistance, and corrosion protection. However, FNC is a high-temperature process (~1000°F), which can temper heat-treated steels—undesirable for critical parts that rely on retained core hardness (like bolts).

Is hard chrome or nickel boron better for a bolt carrier group?

Hard chrome excels in high-heat, high-wear environments without degrading. Nickel boron offers slick operation and easy cleaning but can lose adhesion over time. Compared to nitride, both avoid the risk of tempering previously hardened components and are more stable under high cyclic temperatures.

What’s special about anodizing on AR-15 upper receivers?

Type III hardcoat anodizing converts the aluminum surface into a highly wear- and corrosion-resistant layer. It doesn’t rely on high heat, so it preserves the base metal’s properties. It’s standard for 7075-T6 uppers and lowers and is often layered beneath cerakote or paint for aesthetics.

How do different AR-15 finishes affect corrosion resistance?

Corrosion and heat resistance can vary significantly:

Finish	Corrosion Resistance	Thermal Stability	Notes
DLC	Excellent	Excellent (>1000°F)	Chemically inert, extreme hardness, no heat treatment impact
Hard Chrome	Excellent	Excellent	Military-proven, very stable under sustained fire
Nitride (FNC)	Very Good	Moderate	Can temper hardened steel, softens at high temps
Nickel Boron	Good	Fair	Self-lubricating but can flake or wear over time
Phosphate	Moderate	Good (when oiled)	Holds oil well, needs routine lubrication
Anodized Aluminum	Very Good	Excellent	Applies to aluminum parts like receivers only

DLC outperforms all other finishes in combined corrosion resistance, wear resistance, and thermal stability—making it a top choice for critical steel parts like bolt carriers.

What’s the difference between manganese phosphate and parkerizing?

Parkerizing refers to all phosphate finishes, while manganese phosphate is the specific variant used on Mil-Spec AR components for superior oil retention and durability.

How do nitride coatings hold up to high heat in rifles?

While nitride coatings initially resist wear and corrosion well, they lose surface hardness when exposed to sustained high heat. This makes nitride less ideal for extreme thermal environments, especially where mechanical stresses occur.

Which AR-15 finish holds up best under extreme use?

Under extreme heat, rapid fire, or suppressed shooting, finish choice becomes critical:

Finish	Heat Resistance	Durability	Ideal Use
DLC	Excellent	Exceptional	Suppressed, full-auto, premium builds
Hard Chrome	Excellent	Excellent	Combat/duty rifles, high-volume shooters
Nitride (FNC)	Good initially	Can degrade with heat	General-purpose, semi-auto use
Phosphate	Moderate	Good with oil	Budget-friendly, field-tested platforms
Nickel Boron	Fair	Moderate under heat	Smooth-running recreational builds

DLC stands out as the most heat- and wear-stable option, especially for suppressed or sustained fire applications. It preserves underlying steel properties and outperforms in both high-heat and high-friction conditions.

What are the different barrel finishes available for AR-15s?

Common AR-15 barrel finishes include:

Phosphate exterior with chrome lining (known for heat and corrosion resistance)
Nitride (for enhanced hardness and accuracy)
Bright Stainless (for crisp rifling for precision shooting)
Cerakote (for color-matched barrel and increased corrosion resistance)

Each finish has trade-offs in durability, accuracy, and maintenance.