There are a number of barrels available for the modern AR-15, both from the factory and for the DIY builder. They range from cheap the expensive, long to short, and light to heavy. Basically, every option under the sun is available. Options are good, but too many options are confusing to newer shooters.
The most common barrel for an AR-15 is 16″ in length and is fairly lightweight. This type of barrel fits most people’s needs and is the most common for that reason. When using .223 Remington or 5.56x45mm ammo, it allows shooters to hit targets hundreds of yards away. There are other options though, and one of them might be a better fit.
I have shot AR-15’s with barrels ranging from 10.5″ to 24″ and made of a variety of materials. If you are confused, or bored, let me share my experiences with you and maybe it will help you decide.
The AR-15 was designed by a team of engineers led by Eugene Stoner in the 1950s. They were employed by ArmaLite, a sub-division of Fairchild Aviation. Mr. Stoner had previously designed the AR-10, a full-powered rifle chambered in .308 Winchester. Two of these were supplied to the military for testing and evaluation. When the barrel of one of them blew out, the AR-10 was sentenced to decades of obscurity and the AR-15 was developed.
The AR-15 was a downsized version of the AR-10 and initially had a 20″ barrel. Colt’s Manufacturing LLC, commonly referred to as just Colt, bought the design and the mainstay caliber of the AR-15 became the .223 Remington. Since the AR-15 was designed as a futuristic and lightweight rifle, the barrel was fairly thin at .625 inches.
The 20″ long barrel delivered the vast majority of what the .223 Remington had to give. When the AR-15 was adopted by the US Air Force as the M16, it was chambered in 5.56x45mm. The 5.56x45mm is externally identical to the .223 Remington and is slightly more powerful.
The M16 retained the 20″ barrel in all future revisions, though it was made heavier in profile with the M16A2 model.
After the Battle of Mogadishu in 1993, there was a push to make the M16A2 lighter and more maneuverable. After the development process, the M4 was born. The M4 shares the majority of its parts with the M16A2, but one major change was reducing the length of the barrel to 14.5″. This shorter barrel delivered less muzzle velocity, be was much easier to handle.
The AR-15 has been available in 20″ barrels since its initial development. However, a rifle with the 14.5″ barrel of the M4 isn’t legal for civilian ownership without special licensing, or permanently attaching a muzzle device to make it 16″ for legal purposes.
This gave rise to the popularity of the 16″ barrel. During the AWB, AR-15s made between 1994 and 2004 had either a 20″ or 16″ barrel with no muzzle device. Most AR-15s made prior to 1994 had threads for a muzzle device. Thankfully, when the AWB expired in 2004, AR-15 barrels were again threaded for muzzle devices.
While it is an option to buy an AR-15 with a 14.5″ barrel, the legal necessity of permanently attaching the muzzle device has made it far less popular. This made the 16″ barrel the defacto standard on M4 style rifles and the 20″ barrel standard for M16 style rifles. Remember though, this is a “style” of rifle and not the real thing. Rifles capable of full-auto and 3-round bursts still need special licensing.
For the most part, AR-15s with either the 16″ or 20″ barrel will follow the “government profile”. This is a thin portion of the barrel before the gas block or front sight base (FSB) and a thicker portion after it. This barrel profile makes no sense as it puts the weight where it is least wanted. It has been lampooned for years. Still though, in the 16″ versions it shouldn’t be considered a deal-breaker.
However, I wouldn’t recommend getting a 20″ government profile barrel unless the main goal of your rifle will be to recreate a military rifle. Even in the 16″ barrel, there are better options, just fewer at the budget end of the market.
Since around 2010, manufacturers started experimenting will all sorts of better options than the standard 16″ and 20″ barrels. The improvements include different gas lengths, improved barrel profiles, different metals, barrel treatments, and optics-ready options.
The biggest technical improvement is the development of the mid-length gas system. For the AR-15 to function, expanding gasses from the fired cartridge are fed back into the action and allow it to cycle. After the cartridge is fired, the gasses created by the burning gunpowder push the bullet down the barrel. After the bullet passes the gas block or FSB, part of the gasses get diverted at the gas block and head back toward the receiver. The rest continue pushing the bullet until it leaves the barrel.
The time after the bullet travels past the gas block is called the dwell time. When manufacturers started making AR-15s based on the M4, they increased the barrel length but kept the same carbine gas length. This increased the dwell time with the extra 1.5″ of barrel. The mid-length gas system adds 1.5″ of barrel length before the gas block and removes it after, which gives the 16″ barrel the same amount of dwell time as the M4.
This isn’t to say that a carbine-length gas system on a 16″ barrel doesn’t work, but mid-length gas is an easy improvement with no drawbacks. It is a generally accepted idea that the dwell time can be reduced even further with a 14.5″ barrel having mid-length gas and an 18″ barrel having the same gas system as a 20″ barrel. The result is the bolt moves rearward will less velocity and makes a smoother shooting rifle.
The biggest practical improvement to the AR-15 is replacing the FSB with a low-profile gas block. Since almost all modern AR-15 upper receivers have the ability to have a red dot or optic mounted directly to them, the fixed front sight was just getting in the way. It adds weight and obscures part of the shooter’s sight picture when using an optic. Removing it was a welcome change to most rifles.
The second biggest practical improvement is ditching the government profile barrel for something that makes more sense. Modern barrel profiles add thickness to the barrel prior to the gas block, making it heavier but also giving it the advantage of a thicker profile. Now the barrel is slower to heat and have groups open up. This is done to varying degrees, depending on the needs of the user.
Some 16″ barrels have also been modified to be lighter, reverting to the original thin barrel profile of the M16 but at a shorter length. For a rifle that will primarily be used for shooting inside of 200 yards, this is a great option.
Chrome-lined, Nitrided or Unlined?
This is the important part of AR-15 barrel selection. An unlined barrel shot at a rapid pace will lose most of its accuracy after 2000-3000 rounds. If you see yourself doing that in the near future, consider a chrome-lined or nitrided barrel. nitriding is a chemical process that makes the exterior of the barrel harder and corrosion-resistant. It is also called other names like Melonited and QPQ.
Nitriding a barrel has become hugely popular in the past several years and has largely replaced chrome-lining in the market. Nitriding is cheaper to produce but still offers long barrel life. It is also more durable than the phosphating that chrome-lined barrels receive on the outside.
I have long-term impressions of four AR-15 barrels, which I will detail below.
The first was a chrome-lined barrel made by Green Mountain Barrels. It started life with the ability to shoot good ammunition just under 1 MOA. After approximately 10,000 rounds, it had regressed to about 2.5 MOA. It still had usable life left in it but I replaced it.
The second was a budget stainless steel barrel that came as part of a Palmetto State Armory Freedom series upper. It too was able to shoot quality ammo just under MOA. After about 2500 rounds, it was smoked and shot 3-4 MOA with any ammo I tried.
The third is an FN chrome-lined barrel sold as a Palmetto State Armory premium series upper. It is button rifled, not cold hammer forged. It is not an MOA shooter but isn’t much worse. After about 6000 rounds, it’s still shooting a little worse than MOA, so no real loss of accuracy when compared to new.
The fourth is a Nitride treated barrel from AR Precision. It started as a 3/4 MOA shooter and 2000-3000 thousand rounds later it’s still the same.
Of the two barrels I’m still actively using, one uses a red dot and the other uses a 1-6x optic, so both have more accuracy potential than I need.
So what does it all mean? Chrome-lined and nitride-treated barrels last, while unlined barrels don’t. If you feel a strong emotional pull toward chrome-lined barrels, go for it. They can shoot pretty well. If not, the nitride-treated option is probably better. They are cheaper on the budget end and more accurate on the well-to-do end.
What about Cold Hammer Forged?
Here is where I will probably ruffle some feathers, but I don’t think it’s all that important. FN and Daniel Defense have done a great job of marketing their CHF barrels, and they both do indeed make quality barrels, but in my opinion that it’s just another way to make a barrel.
Part of my opinion on this is formed by being old enough to remember Remington not wanting to advertise how their barrels were made, because of the older perception that CHF barrels were inaccurate. However, the bigger part is the lack of motivation by the companies who sell CHF barrels to document how much better their barrels are in semi-auto rifles.
Either company could easily subject two barrels to the same firing schedule and publish the results, but they don’t. Until I see the results, I think their primary interest in selling CFH AR-15 barrels is additional product mark-up.
The most common argument I’ve heard in favor of CHF barrels starts with “All things being equal…”, and they never are. Ammo budgets, firing schedules, and accuracy expectations are never equal. Neither are manufacturing tolerances. This is why predicting any barrel’s life outside of structured shooting disciplines is very hard.
One myth that I will take a few precious minutes to debunk is the idea that a CHF barrel is denser than a button-rifled one. This defies physics and would require the button-rifled barrel to have some kind of cavities inside of it. Matter can’t be compressed beyond a certain point without the incredible pressures produced by a star. It’s called electron degeneracy pressure and it’s what keeps a CHF barrel from collapsing in on itself and forming a neutron star. Or worse, a black hole.
Seriously though, find two barrels with the same profile but one is CHF. They will have the same advertised weight. The BCM 16″ mid-length button-rifled barrel is listed at 1 pound 12 ounces, as is the BCM BFH option. It would blow your mind right out of your head if I showed you the Green Mountian 16″ mid-length barrel is one-tenth of a pound heavier than either. Don’t worry though, it’s not denser, because that would defy physics. It just has a slightly different profile.
The most accurate AR-15 barrels made are constructed from stainless steel. This point really isn’t up for debate. For any stainless steel barrel that shoots no better than a nitride-treated barrel (stainless or carbon steel), I don’t really see the point. If they start out with the same accuracy potential, the nitride-treated barrel will be out-shooting it when the round count stacks up.
How Much Accuracy Do I Need?
Now, this is an interesting question because it isn’t the same for everyone. I’ll list some common shooting needs below.
If you are a casual shooter and will be using iron sights, your accuracy needs are pretty minimal. The vast majority of barrels, save ones with actual issues, will meet your needs. The odds are good you’ll mostly be shooting budget factory ammo anyway, which isn’t prone to accuracy itself. The iron sights will be the main limiting factor. Budget barrels with long-lasting nitride treatment are made for you.
If you plan on using a red dot, much of the above applies. Most people are more accurate with a red dot than standard iron sights, but still aren’t going to shoot 2 or even 3 MOA at any distance. Once again, a budget nitrided barrel is a good fit for you.
If you plan on shooting inside of 300 yards, and mostly shooting in unsupported positions, the same advice applies.
If you are like me and like using a low-power variable optic, like a 1-6x, there are benefits to getting a better barrel. At 6x and in a good shooting position, it is easy to have accuracy suffer because of barrel quality and not some other limiting factor.
The same can be said for anyone attaching a medium power optic and shooting primarily “match grade” ammo. There are benefits to buying a barrel capable of sub-MOA when using a magnified optic.
What Twist Rate Should an AR-15 Barrel be?
The best answer is 1:7 or 1:8 if you don’t plan on shooting bullets lighter than 55-grain FMJBT. This encompasses all common target ammo in both 5.56x45mm and .223 Remington. For the most part, shooters have stopped believing in the accuracy downfalls of over-stabilizing a bullet, or spinning it too fast in layman’s terms. Modern bullets down to 40-grains can be shot through fast twist barrels at 5.56x45mm pressures and still shoot great.
On the other end, I’d recommend staying away from 1:12 and 1:14 barrels unless historical accuracy is important as part of a nostalgia build. They do work, they will stabilize the 55-grain FMJBT practice ammo, and there are good lightweight defensive bullet options available as well. But, I don’t see the upside.
In the middle is the controversial twist rate of 1:9. Like 4140 steel, it too has picked up a stigma for only being used in cheap guns. This stigma is more true than false. Still, it’s not a bad twist rate, but it doesn’t have any advantages over 1:8 or 1:7. It will stabilize all common practice ammunition, some good long-range options, and good defensive bullets.
If I had a 1:9 barrel I’d continue using it, I just wouldn’t buy a new one. Part of the problem is even finding a quality 1:9 barrel these days.
Traditional Rifling vs 5R and 3R?
The best barrels in the world use land-and-groove riflings, so it can’t be that bad. In my opinion, a quality barrel with any form of rifling works. It is not something I would recommend obsessing over.
What Barrel Length?
16″ barrels are still the do-all option. Plan on losing 100-200 FPS when compared to shooting a 20″ barrel. If you aren’t pushing the distance envelope of the platform, they are a great option. This velocity loss is a bigger deal for military users than civilian gun owners. The two most popular military ammunitions, the M193 and M855, need lots of velocity to fragment.
Civilians shouldn’t be using these two ammunition types for anything other than target practice. Soft point, hollow point, and expanding copper bullet perform well at lower velocities. For defensive ammo, don’t load your gun with trash.
Another popular option is shooting a barrel slightly shorter than traditional for a gas length. The best example of it is an 18″ barrel with rifle-length gas. I’ve shot them, and they are both smooth shooting experiences, but it’s not a night-and-day difference over a good 16″ barrel with mid-length gas. The improvement is modest, but there.
Chalk me up as a fan of the 16″ mid-length barrel or the 18″ rifle-length barrel unless a reason exists not to get one. The only recommendation I have against an 18″ barrel is if the price spikes over the 16″ barrel.
5.56 vs .223 Wylde?
The best modern barrels will have a .223 Wylde chamber, or some variation of it. Once you start looking at any mass-produced barrel and shooting 2/3rd MOA is a realistic expectation, I don’t think the chambering difference matters. It certainly doesn’t matter on budget rifles.
The .223 Wylde chamber should be tighter in dimensions than the 5.56 chamber, but 5.56 chambers can be all over the place. The goal of .223 Wylde is to have the tightest chamber possible and still be safe to shoot 5.56x45mm ammo. I wouldn’t recommend a .223 Remington chamber without some specific reason to get it.
In my life, I have heard one experienced shooter say they have seen reliability problems with a quality .223 Wylde chamber. The owner of it, whom I have not met, sounded like the “ARs don’t need to be cleaned, just oiled” type. Take this anecdote for what it is worth.
What do you Recommend?
There are a number of good brands out there, and hopefully, if you have read this article you’ve realized several options exist. For building, I think the sweet spot between shooting sub-MOA and paying a reasonable price is between $150 and $225. AR Precision, Faxon, and Ballistic Advantage offer a wide variety of sub-MOA barrels at this price range.
I tend to prefer the lighter-weight barrels that still use the common .750 gas block. I don’t like carrying around lots of weight in my barrel when I run a nearly 2-pound optic in the Vortex Razor Gen II 1-6x24mm.
Palmetto State Armory Freedom series offer acceptable barrels, both for sale and in their rifles. These are good options for people who plan on shooting budget ammo with iron sights or a red dot. For something more accurate, but not heavily over-priced, I think Aero Precision offers a good barreled receiver or complete rifle.
I don’t point people toward very expensive options like Danial Defense or BCM. They are good guns, you can load them with ammo and shoot things with them. But, I think you’ll just be spending extra money for the same shooting experience.
For all of these recommendations, I advise you to steer clear of the stainless options and focus on the nitride-treated ones.
If you must have a chrome-lined barrel, Green Mountain Barrels or an FN overrun would be my recommendation.
Maybe you want to pay more for a CHF barrel, but I don’t.