QPQ Nitride vs. Chrome Lining: Which is The Better Barrel Finish?

Maybe you’re buying your first AR-15, or upgrading your upper. Or maybe you’re building one from scratch. Either way, you’ve figured out what specifications you want in your barrel — length, gas system, twist rate, caliber — except for one:

What barrel finish will you choose? QPQ nitride or chrome lining? Which one’s better, and how so?

What is QPQ Nitride?

quench-polish-quench nitrocarburizing case hardening — that’s a mouthful, so most just call it “ntiriding,” or its trademark name, “Melonite” — is a conversion coating that protects the steel inside the bore from heat and corrosion. Nitride looks like a slick, black finish similar to bluing. And it is, in fact, similar to bluing.

Benefits of Nitride

Nitride an incredibly hard finish that penetrates the top layer of the steel and converts it into an oxide layer using a molten liquid salt bath and high heat. The process adds nitrogen and extra carbon atoms that fill in the steel’s porosity.

Nitriding Maintains Maximum Accuracy

Because the nitriding process is a conversion coating and only treats the bore’s existing steel, it doesn’t add physical dimension to the inside of the bore. And the “P” (polish) in “QPQ” ensures the finished nitride surface is dimensionally perfect — arguably with an even better and smoother finish than the raw bore received during its manufacture. This is a huge advantage for a barrel with rifling that was already precisely machined for maximum accuracy.

Nitriding Makes Cleaning The Barrel Easier

Nitrided surfaces have low porosity and high hardness and lubricity. In other words, nothing sticks to them well, even when subjected to chemicals and high heat. This allows the bore to stay relatively free of carbon fouling and copper deposits, even after extensive firing.

Cleaning a nitrided barrel is incredibly easy, too. Because fouling and copper can’t stick to the bore’s surface, a few quick swabs with a bore brush, and a patch or two soaked in CLP are all you need to clean your barrel.

Nitride is Incredibly Resistant to Corrosion

Got a thing for corrosive surplus ammo? Hate cleaning your AR, and think it should just sit dirty? Then the nitrided barrel’s for you. Even without cleaning, your bore will remain insulated against corrosion and rust from fouling, so you won’t suffer decreased barrel life or any loss in accuracy if you’re not the shooter who likes to clean their rifle after every range day.

What is Chrome Lining?

Chrome lining’s been around for decades, and it was originally developed for fully automatic weapons in military service. Chrome lining is an additive coating that involves cutting the bore and its rifling larger than the caliber’s intended diameter, then depositing a chromium alloy using electroplating to obtain the bore’s final dimension.

Benefits of Chrome Lining

Because it’s an additive coating, chrome lining physically separates and insulates the bore from corrosion and heat, effectively making the bore itself impermeable to damage and a loss of accuracy for the life of the lining.

Chrome is Unbeatable At Resisting Heat

Like we said, chrome lining was made to protect machinegun barrels from sustained automatic fire, and it does this job phenomenally. You’ll struggle to put a dent in a chromed barrel using a semiautomatic action. It’ll likely take literally hundreds of rounds being fed nonstop before a chrome-lined bore even begins to approach a point of mild stress.

Chrome Lining Will Outlast The Gun

Because chrome is physically deposited into the bore, and because it’s so effective at resisting wear, the typical chrome-lined barrel will outlast most other components. While the typical centerfire rifle barrel, left uncoated, will produce acceptable accuracy for 4,000 to 8,000 rounds — depending on muzzle velocity and caliber — a chrome-lined barrel will last at least 15,000 to 25,000 rounds, if not longer.

Chrome Bores Are Also Easy to Clean

Like nitride, chrome provides a non-porous, incredibly hard surface with a naturally high level of lubricity. That means copper and carbon won’t stick well to the rifling inside, so cleaning is a breeze. And if you hate cleaning your rifle after every range day, just leave it be — the chrome inside the bore won’t allow fouling to penetrate the steel, so it can’t corrode the rifling.

So, Which is Better? Nitride or Chrome?

We’ll keep it simple: If you want maximum accuracy, stick with nitride. If you want maximum barrel life, go for chrome lining.

Nitride is More Accurate

Although modern chrome-lined barrels are capable of producing sub-MOA accuracy, the QPQ nitriding process will always better preserve the inherent accuracy found in a freshly machined barrel. This is particularly true if you paid extra for a precision-cut bore from a top-tier barrel maker.

Though don’t discount chrome lining: It’s still a better than an uncoated bore, even if accuracy is your primary concern. Modern chrome-lined barrels still produces incredible accuracy out to hundreds of meters.

Chrome Will Last Longer

While nitride is incredibly tough, it’s also incredibly thin. During the nitriding process, the chemical conversion only penetrates a few microns into the surface of the steel. So, as it wears, nitride will eventually give up some of its protection against heat and corrosion.

Chrome linings are significantly thicker than nitride-treated surfaces and, since it has a similar hardness rating to nitride, chrome will simply last a lot longer. Chrome is also more resistant to heat than nitride, so if rapid fire and tactical mag dumps are your favorite things to do at the range, chrome is, again, the better choice.

Decided on a barrel, now? Here’s how to build your AR-15 upper.