AR15 BCG finishes (l-r) Toolcraft Titanium Nitride, BCM BCG with Robar NP3+, Toolcraft Nickel Boron, Toolcraft Black Nitride, Colt BCG refinished in Chrome with Nickel Boron Gas Key, Toolcraft Diamond Like Carbon (DLC) Finish, Toolcraft Chrome Phosphate
There are a wide variety of finishes available for AR-15 bolt carrier groups (BCGs). Each finish has its own unique color ranging from silver to gold to black and various shades of each. Let's compare three of the best black finishes and see how they stack up.
Toolcraft BCG with Manganese Phosphate finish
Phosphate, also known as manganese phosphate or parkerizing, is mil spec for bolt carrier groups in military rifles like the M16 and M4. Phosphating involves submerging the metal parts into a phosphoric acid solution at 200 degrees Fahrenheit for 30 minutes. Properly manufactured BCGs with a phosphate finish will have a chrome lining inside the gas key and inside the carrier where the gas rings ride. For this reason they are often called Chrome Phosphate BCGs.
The phosphate provides a long lasting resistance to corrosion. It is very common because it is inexpensive, durable and easy to apply. A phosphated surface generally has some texture to it which can allow it to "hold oil" better than other finishes. This rough surface can be more difficult to clean though. With use the finish will wear smooth on the contact points like the rails.
Durable and corrosion resistant
Rough finish that requires more lubricant to run smoothly
Rough surface makes cleaning more difficult
Toolcraft BCG with Black Nitride finish
Also known as Melonite, Salt Bath Nitride, Tennifer, Quench-Polish-Quench (QPQ) or simply Nitride, this is a heat treating process that creates a case hardened surface by diffusing nitrogen into the metal surface. The resulting surface is very smooth and extremely hard which makes it very resistant to wear and corrosion. Because nitrided bolt carrier groups do not require chrome lining of the gas key or inner areas of the bolt carrier, manufacturing costs are reduced. Black Nitride finished BCGs often have an attractive deep black finish.
High durability and corrosion resistance
Smooth finish requires less lube
Easier to clean than phosphate
Can cost more than phosphate
Diamond Like Carbon (DLC)
Toolcraft BCG with Diamond DLC finish
Ionbond Diamond Like Carbon (DLC) Coating is a state-of-the-art metal finish applied through a Physical Vapor Deposition (PVD) process. It is an extremely tough, corrosion proof coating, with excellent low-friction properties. Ionbond Black DLC will not chip, crack or peel, providing you with years of reliable function and protection against wear. It is so strong that it is virtually scratch proof. It has an attractive gray graphite-like appearance. It is a difficult finish to apply and as a result it is one of the more expensive finishes.
Extreme hardness and corrosion protection
Smooth with low coefficient of friction
Phosphate vs Nitride
These are two of the least expensive finishes available. Nitride has the edge when it comes to smoothness and hardness. It also requires less lubricant to work well and is easier to clean. Nitride has many advantages but it is not mil-spec for BCGs and that is an important consideration for some.
Phosphate has been serving the military well for many years and it works very well. For the traditionalist, a phosphate BCG has a texture that just feels right. Either will get the job done. On the basis of performance, nitride wins. For nostalga, phosphate wins.
Nitride vs DLC
The battle between these two smooth finishes comes down to cost vs performance. Both are excellent finishes that are very hard, smooth and high performing. DLC outperforms nitride by about the same amount that nitride outperforms phosphate. This is on the basis of hardness and corrosion resistance. It is just a question of how much performance you want to pay for. Both are far beyond ordinary. On the basis of bang for the buck, nitride wins. If you have the money, DLC wins.
DLC vs Phosphate
These two BCG finishes could not be more different and are on opposite ends of the spectrum. For hardness, corrosion resistance, smoothness and ease of cleaning, DLC wins. For nostalgia and tradition, phosphate has no competition.
All of the finishes listed here are quality finishes and a good BCG will work fine with any of them. Each is a great option if you are looking for a BCG with a black finish.
For a detailed look at Nickel Boron see: Top 3 Reasons You Might Want a Nickel Boron BCG
For a detailed look at DLC see: Toolcraft DLC BCG Review - The Best BCG Ever Made?
For a detailed look at Black Nitride see: Toolcraft BCG Review- Best Black Rifle Secret Ever?
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