AR-15 Barrels 101

By Jerry Kraus published on in AR-15, Guest Posts, How To

One of the biggest differences in cheap versus high-end AR-15s is the quality of the barrels. We are going to cover the pros and cons of Mil-Spec chrome molly steel chrome-lined barrels versus match-grade stainless steel, non chrome-lined barrels and help you make an educated decision on which is right for the intended purpose of your next AR-15.

Two black chrome-lined barrels, stacked on top of each other, on a white background.

Although it is unlikely that most of us will ever “shoot out” a barrel; chrome-lined barrels handle extensive shooting and adverse weather much better.

Most AR barrels fall into one of two categories: either they are made of chrome molly steel with a chrome-lined bore and chamber, or they are made of stainless steel, which typically does not have chrome lining in the bore or chamber.

First, let me say that if the bore (barrel) is chrome-lined, the chamber will be as well and likewise, if the bore is not chrome lined, the chamber will not be either. Chrome molly steel is harder than stainless steel but our main focus is going to be on the chrome lining vs. non-chrome lining aspects because that is what will have more effect on AR-15 shooters.

The Pros and Cons of Chrome Molly Steel Barrels

M16/M4 Mil-Spec barrels are made of chrome molly steel with chrome lined bores (and chambers). So let’s detail the pros of chrome molly steel barrels that have chrome lined bores and chambers first.

The Pros of Chrome-Lined Barrels

The military loves chrome-lined barrels because of:

  1. Corrosion Resistance.
    This is especially important in wet and saltwater environments. When the military issues M16s to our troops in Vietnam, it was initially issued without a chrome lined chamber, or chrome lined barrel, and without a cleaning kit. This, combined with a very corrosive powder and the wet jungle environment of Vietnam, caused countless deaths to our own troops mainly because of failures to extract the spent round in the chamber during combat. The only way to clear a failure to extract is to run a rod down the barrel and knock the spent round back out. According to the article “Defense Under Fire” in Time magazine dated 9 June 1967; “We left with 72 men in our platoon and came back with 19. Believe it or not, you know what killed most of us? Our own rifle. Practically every one of our dead was found with his [M16] torn down next to him where he had been trying to fix it.” —Marine Corps Rifleman, Vietnam. Though eventually remedied, it illustrates the value of chrome-lined barrels and chambers.
  2. Extended Barrel Life.
    This is the biggest reason the military uses chrome-lined barrels. Every round down range creates heat in the barrel from the hot gasses that the powder creates and the friction of the round, both of which result in barrel erosion over time. The higher the velocity of the round, the hotter the barrel gets resulting in even more barrel erosion. The faster the rounds fire in succession, such as on full auto in the military, the hotter the barrel gets and stays hotter, longer, all resulting in drastically more barrel erosion thus substantially shortening the barrel’s life, commonly referred to as “shooting out” the barrel. An AR-15 with a Mil-Spec barrel identical to the Mil-Spec barrel of the M16 will last roughly twice that of the M16 barrel. This is largely due to the fact full auto rates of fire are exponentially detrimental on barrel life. Non chrome-lined barrels wear out even faster with full auto fire, this is the biggest reason the military uses chrome-lined barrels. Most people, however, will not be able to “shoot out” a chrome-lined AR-15 barrel in their lifetime, and if you do, you should consider yourself very fortunate to be able to shoot this much! “Shooting out,” or wearing out the barrel, will become evident when you can visibly see your chrome disappearing in your bore and your groups keep getting bigger and bigger.
  3. Ease of Cleaning.
    This is a definite side benefit of chrome-lined barrels and chambers. Some people think this is only slightly easier to clean, however my experience is that it is substantially easier and faster to clean. So, in short, chrome-lined barrels protect you from erosion and corrosion and easier cleaning is a bonus!

The Cons of Chrome-Lined Barrels

The biggest disadvantage of chrome-lined barrels is long-range accuracy. When a barrel is chrome lined, even with the best technology available today, it is not perfectly even. Because it is not perfectly even on the inside of the barrel, there are very slight high points that obviously will negatively affect the accuracy of the bullet. However, this is only noticeable at long ranges. There are plenty of chrome-lined barrels out there that will give you sub-MOA accuracy, which means a three-round group in less than one-inch at 100 yards.

People will disagree as to the ranges it becomes noticeable, but it is the author’s opinion that it is beyond 300 yards—beyond three football fields. Just to be very clear, the average soldier or civilian with some training should be able to hit a man-sized silhouette target at 300 yards with an AR-15/M16 that has chrome-lined barrel.

Even with a chrome-lined barrel, the biggest factor holding back the shooter’s accuracy beyond 300 yards is going to be shooter error, lack of training, or practice for probably 90 percent of the shooters out there.

The Pros and Cons of Stainless Steel (Match Grade) Barrels

A single stainless steel, match grade barrel on a white background

Match grade barrels offer few advantages at ranges below about 300 yards, but at that distance and especially beyond, the accuracy difference becomes obvious. This makes stainless steel, match grade barrels and absolute must for long-range target shooters.

The second major category for AR barrels are stainless steel barrels, which are typically not chrome lined in the bore or chamber, and these are known as “Match Grade” barrels.

The Pros of Stainless Steel Barrels

Extreme benchrest shooters, NRA High Power Long Range shooters and Civilian Marksmanship Program (CMP) shooters all demand “match grade” barrels—meaning barrels made of stainless steel that are NOT chrome lined. “Match grade” barrels are more accurate and the longer the range, the more apparent this becomes.

The Cons of Stainless Steel Barrels

The cons of match-grade barrels are that they wear out faster, they are harder to clean and they don’t resist corrosion as well as a chrome-lined barrel. Again, let’s clarify that most shooters will not wear out even a match grade barrel in their lifetime. As far as cleaning goes, if the barrel is broken in or “shot in” correctly, the barrel will have a burnishing that minimizes fouling and subsequently makes the barrel much easier to clean; however, still not as easy to clean as a chrome-lined barrel.

Which Barrel is Right for You?

So you’re probably wondering which is right for you, right? An AR-15 rifle is merely a tool, a tool for doing a job. Which job do you want your AR to do?

The Ideal Barrel for defense or Plinking-to-Medium Range Target Shooting

If you are like most people you are you picking out a tool that would be ideal for you to defend your family, your ranch or your home with and maybe do some plinking to medium-range target shooting.

On the other hand,  maybe you want an AR for the commie invasion of the USA or the total collapse of society? Or even, as my younger friends ask me, “What AR do I want for the zombie apocalypse?”

If the answer is yes to any of these questions, then I would choose an AR-15 with a chrome-lined barrel and chamber. These are very common and is the same barrel configuration the military uses. I wouldn’t care if it was cold hammer forged or not, and if so, that would be a bonus.

The good news is ARs with these features are very affordable. There are two I like for under $900 from www.CheaperThanDirt.comArmalite M15A4 and the Bushmaster Optics Ready Carbine (OBC).

I would also encourage you to get one for your wife or girlfriend when you can afford it as well. If the unimaginable happens, you will wish she had one and knew how to use it.

The Ideal Barrel for Extremely Long Distance Shooting or CMP Matches

Fluted barrel in dark gray on a lighter gray background

Let’s face it fluted barrels just look cool. More importantly, the fluting reduces weight and dissipates heat at a much quicker rate than straight stock barrels.

I know what you are thinking, “What if I want a gun that can shoot accurately at extreme distances because maybe I am thinking about participating in state or national CMP matches?”

What you want is an AR with a stainless steel non chrome-lined match-grade barrel, cold hammer forged would be a bonus. In this category, www.CheaperThanDirt.com offers an AR I like for under $1300 – the Rock River Arms (RRA) LAR-15 National Match A4. Rock River Arms is a high quality manufacturer and they won the contract to supply the DEA with AR-15s.

Now you have a better understanding of AR barrels and chrome lining and what will work for your needs. Next we will cover .223 chambers versus 5.56mm chambers and more!

Until then, shoot safely and shoot often!

Jerry Kraus is a U.S. Army Airborne Infantry veteran and competitive shooter. He has hunted big game in Alaska and Africa. Jerry is a frequent freelance writer published in Soldier Of Fortune magazine. Feel free to connect with him on Facebook or LinkedIn

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