4150 vs. 416R Stainless: Which AR Barrel & When?

Stainless barrels have gained popularity rapidly. In the past few years, they've taken the AR-15 market by storm. Nowadays, you'll find plenty of accuracy-focused upper receivers and prebuilt rifles configured with 416R stainless barrels. But 4150 barrels -- commonly called "carbon steel" barrels -- remain arguably the most popular.

So, which is better: 416R stainless, or 4150? Why choose one or the other?

What is 416R Stainless?

Of all the available options, 416R is the stainless gun barrel steel to pick. Developed by Crucible Industries specifically for precision rifles, this variant of 416 stainless is designed to provide maximum machinability to ensure barrel rifling can be cut with extreme precision and uniformity, increasing accuracy, while its high chromium content is meant to promote easier cleaning and better resistance to corrosion from burnt powder and carbon fouling, improving barrel life.

416R is also pre-hardened before it's ever turned by a barrel maker, ensuring uniform hardness to -- you guessed it -- further promote uniform machining and finishing for yet more improved accuracy.

What is 4150?

4150 is the "mil-spec" barrel steel of the AR-15 world. It's still in use today by the U.S. military and various other armies globally. This high-carbon steel provides incredible hardness, ensuring the barrel's rifling can withstand frequent, rapid semiauto and automatic fire, and it affords an overall long barrel life regardless of maintenance or the firing schedule.

Which Barrel Steel's Better?

Neither. Each barrel steel is better at performing certain tasks relative to the other, while also suffering some drawbacks that limits its effectiveness in other ways.

4150 Barrels Last Longer

Contrary to popular belief, stainless steel -- even with 416R's particularly high chromium content -- is not harder than 4150 steel. In fact, its a softer steel than 4150. That's why it's used to make accurate barrels in the first place: Its lower hardness makes machining easier, which allows for more precise rifling to be cut into the barrel.

4150 barrels, given their higher hardness, last longer. Where a 416R barrel may provide good accuracy for 4,000 to 8,000 rounds (depending on the caliber) before groupings begin to widen noticeably, a carbon steel barrel can retain good performance for 10,000 to 20,000 rounds, depending on the firing schedule and how often it's cleaned to reduce corrosion.

416R is Far More Accurate

When we say 416R is more accurate than 4150, it's not by an insignificant amount. Where the typical button-rifled 4150 barrel might provide 1 to 2 MOA of accuracy, a 416R barrel of the length length, manufactured using the same methods, can easily provide sub-MOA accuracy, even with "cheap" off-the-shelf ammunition.

4150 Withstands Heat Better

Being a softer steel, 416R is more susceptible to degradation from heat. If you're the type of shooter who likes to dump magazines or generally fire rapidly, 4150 will be a better choice. 416R is best suited for a relatively slow cadence, where 2- to 5-round groupings are placed on target at a considered, deliberate pace.

416R is Easier to Clean

Stainless barrels are far easier to maintain. Even with a chrome lining or nitride treatment, 4150 barrels tend to get "sticky" after they're fouled, so they require more brushing, solvent soaking, and wiping to remove carbon and copper debris. Stainless barrels are incredibly easy to clean, often requiring just a few swabs of a brush, followed by one to two lightly oiled patches to remove the same fouling.

If you're the type who shoots often and you want to reduce your after-range cleaning sessions from 30 minutes to 5 or 10, a stainless barrel might be the better investment -- and you'll enjoy more accuracy to boot, too.

So, Which Barrel Should I Pick?

Pictured: M4A1 Clone AR-15 Kit w/ 16" 4150 Barrel

We'll keep it simple: If you're building a "SHTF" AR-15 or a home defense gun, or if you simply want a barrel that's nearly guaranteed to outlast you -- and if the gun in question is to be chambered in 5.56 or .223 -- it's best to stick with a 4150 barrel.

But if you're interested in seeing just how much accuracy and range you can squeeze out of the AR-15 (like those shooters who easily take 5.56 and .223 match ammo out to 600 yards or more) you'll want to grab a 416R barrel.

"What If I'm Not Chambering 5.56?"

Pictured: 6.5 Creedmoor Long-Range AR Kit w/ 20" 416R Heavy Barrel

If you're chambering a different or larger cartridge in your AR platform -- especially any 6.5mm cartridge, like Grendel or Creedmoor, or .308 Winchester -- you should seriously consider opting for a stainless barrel. Those rounds, and most other cartridges found in the AR platform today, are capable of providing good accuracy at 1,000 meters or more -- and it's at these distances that the advantage of a stainless barrel really becomes noticeable.

(What About "CMV" Steel?)

CMV is basically a variant of 4150 steel. It's so similar that most AR-15 manufacturers and barrel makers simply advertise "4150 CMV" when they're talking about carbon steel barrels. We cover the differences between all barrel steels -- 416R, 4150, and CMV -- in detail in our In-Depth to AR-15 Barrels. Ready it next to learn more!