The AR-15 is well known as America’s rifle, as it is currently the most popular centerfire rifle in the United States, with over sixteen million rifles in circulation.
If you are going to be building your own personal AR-15 rifle, one of the most important considerations to take into account will be the barrel length.
In this article, we will cover the many different factors that you will need to consider when choosing a barrel for your personally built AR-15 rifle or carbine.
Cold Hammer vs. Mil-Spec Barrels
The vast majority of AR-15 users use a standard mil-spec barrel. It works for most purposes, including over the long term, and is made out of chrome molly steel.
Most budget AR-15 carbines such as the Ruger AR-556 or Smith & Wesson M&P15 Sport II have a mil-spec barrel.
That being said, if you really want to get the most out of your money by getting a barrel that will really perform well, the cold hammer forged barrel will be better.
This barrel uses a hydraulic machine to hammer the blanks in the barrel from multiple sides at once, which simply creates a tougher barrel with a longer life-span than the mil-spec version.
A cold hammer barrel will cost around a hundred dollars more than a mil-spec one.
Chrome vs. Stainless Steel Lining
Next, you will need to choose between a chrome or a stainless steel lined barrel.
Chrome lining is commonly used by the military because it is very resistant to salt water and moisture and humidity and can protect against rust and corrosion.
Furthermore, the chrome also protects the barrel from heat as well, which gives it an overall longer lifespan. It’s easier to clean than a stainless steel barrel as well.
That being said, chrome lined barrels are also not quite as accurate as stainless steel barrels over long distances, though you’re not really going to notice much of a difference until you’re tapping targets out to around three hundred yards or so.
Barrel Twist Rates
The twist rate of an AR-15 barrel refers to the number of rotations that the fired bullet will make for every inch traveled in the barrel.
In other words, a barrel with a 1:7 twist rate means that it will make one complete rotation in seven inches before it exits the barrel, which would also mean that it travels faster in contrast to an AR with a 1:9 twist rate.
Twist rates are important because they dictate which bullet weight of ammo will fire the best in your AR-15.
For reference, you can use this chart:
- 1:12 Twist Rate – 35-50 Grain
- 1:9 Twist Rate – 45-70 Grain
- 1:7 Twist Rate – 69-90 Grain
The profile of your barrel refers to the thickness of it. This has a direct impact on the performance of your barrel, such as how accurate it is as well las its rigidity.
It also dictates how long it will take before the barrel heats up, and the hotter the barrel, the less accurate it will be.
The weight of your AR-15 barre; is also vitally important, and what’s most important is the moment of inertia, or the distance from the mass to the force as the rotation is applied. This is measured usually in foot per pounds.
For this reason, a muzzle break on a 20 inch AR barrel is going to feel heavier than the identically same muzzle break on an AR barrel that is 16 inches or less.
There are a number of different AR-15 profiles and weights to choose from as well.
For example, the M16 style of AR rifle has a 20 inch rifle long barrel that is lightweight and with a 1:12 twist rate. The bore is not chromed, which helps to keep the weapon light as well.
Such a barrel profile and weight is often referred to as a pencil barrel, also known as an A1 barrel.
It’s a great choice for single semi-automatic shots, but not the best fully auto or for extended firing sessions.
This is why the Marines later requested the M16A2, which has a chromed bore and a heavier bore barrel to handle fully automatic or three round burst fire, or extended firing sessions.
NOTE: this is the primary difference between the M16A1 and the M16A2 rifle barrels.
Right now, however, the M4 style of AR rifle is by far the most common, and in the hands of civilians, the 16 inch barrel is the most common because it’s the shortest available legal length without reducing the carbine down to being classified as a pistol.
The M4 barrel is designed to be lightweight right underneath the hand guards, right before it reaches the gas port. These barrels are designed for general purpose use with the typical infantryman.
Being lightweight, they do heat up faster, which as we discussed a minute ago can reduce accuracy.
Beyond distances of three hundred yards or so, you’re probably looking at chances from 1.5 to 2 MOA up to around three to four MOA.
That’s not terrible for combat or tactical use, though for competition shooting it will be a problem.
In short, the heavier and thicker the barrel profile, the best it will perform in terms of accuracy, fully automatic fire, and for keeping heat down to a minimum.
Pencil barrels do work well, but only for semi-automatic fire at a reduced firing rate.
Barrel Lengths: Which One Is Right For You?
The three most common AR-15 barrel lengths for civilians are 16 inch, 18 inch, and 20 inch barrels. This does not include the extraordinarily long AR rifles or the short AR pistols, but for the purposes of this article we’re sticking with rifles and carbines.
Out of these, the 16 inch barrel is definitely the most common, as it is the shortest legal length for civilians and therefore the most maneuverable.
However, the 20 inch is the original barrel length, while some people prefer the 18 inch barrel as a compromise between the two.
The 20 inch barrel will shoot the bullet faster than the 16 inch, and it also has a longer sight radius to help with more accurate shooting, but at the cost of a less maneuverable rifle.
Some people claim that the 20 inch barrel AR-15 is the more reliable since it’s the original design as well, though honestly, 16 inch barreled AR-15s are perfectly reliable too.
So, which barrel length is truly the best for you? It depends on whether you want a rifle that is shorter and more compact or if you want a rifle with superior velocity and potentially greater accuracy.
Again, some people prefer the 18 inch barrel as a compromise, though they aren’t as common.
For a beginner rifle, however, you should know that there are a variety of budget AR-15 carbines with a 16 inch barrel, but that AR-15s with a longer 18 or 20 inch barrel will cost you a few hundred dollars more.
For reference, a 20 inch barrel on an AR-15 will make the rifle an M16-style of rifle, while a shorter 16 inch is very similar to and M4 style of rifle.
If your barrel length is less than 16 inches, or overall length of your rifle less than 26 inches, it will be considered a SBR (Short Barreled Rifle). These weapons are covered under the National Firearms Act (NFA), and you need a tax stamp from the ATF.
Popular AR-15 Cartridges
Here are some of the most popular AR-15 cartridges that AR barrels are made for:
The 5.56x45mm NATO is by far the most popular caliber that the AR-15 is chambered in, and it can also chamber and shoot .223 Remington as well. The 5.56 is very plentiful, available, and affordable.
For a beginner user of the AR rifle, the 5.56 is simply the most versatile choice.
A rifle with a .223 Wylde chamber is used on .223 rifle barrels to ensure that they can safely chamber and fire both the .223 Remington and the 5.56x45mm NATO rounds.
This way, the barrel exploits the accuracy advantages that the .223 Remington round provides while handling the hire pressure of 5.56.
.300 AAC BLACKOUT
The .300 AAC Blackout was designed for use in AR rifles while also having ballistics very similar to the 7.62x39mm round that is chambered and fired out of the AK-47 rifle. It will still function with normal AR-15 5.56 magazines.
The 6.5 Grendel round is designed to provide superior power than the 5.56x45mm NATO round while less power than the .308 Winchester, and is therefore viewed as an intermediate cartridge for the AR-15 rifle platform.
It is a good choice for medium sized game such as deer and antelope as well.
Last but not least, you can also go with a pistol caliber AR, in which case the 9mm Luger will be the best bet.
9mm is very plentiful and available, and certain AR rifles chambered for 9mm Luger will accept Glock magazines as well.
Best AR-15 Barrels on The Market
In this section, we will outline and discuss some of the very best AR-15 barrels and manufacturer on the market today:
The Faxon .300 AAC Blackout Gunner Barrel is built out of a hardened 4150 chrome moly with a rigid contour to help aid in accuracy as well as to prevent the rifle from overheating.
That being this, this barrel is also very lightweight to help make it as maneuverable as possible.
It is chambered for the .300 AAC round. Being chambered for the .300 AAC, an AR-15 with this barrel will have very similar ballistics to the 7.62x39mm round like is chambered for the AK-47.
This is a flame fluted match barrel from Faxon Firearms that has a number of features, including a black nitride finish to help reduce rust and corrosion, a 1/2/2-28 TPI threaded muzzle, and a 1:8 twist rate.
This rifle is also chambered for the .223 Wylde round, and is available from 14.5 up to 20 inch barrel lengths for mid length and rifle length gas systems.
The .223 Wyde is a hybrid .223 and 5.56 chamber that is designed to give the accuracy advantage of the commercial .223 Remington round with the high velocity 5.56 ammo.
One of the more heavy pencil barrels on the market is the .223 Wylde pencil profile match barrel, featuring a 1:8 twist rate, an NP3 coating to help reduce rust and corrosion, and a threaded muzzle.
This barrel is built out of a stainless steel 416-R material in Ohio, and delivers premium performance with each shot.
As a .223 Wylde barrel, this barrel will have better accuacy because teh chamber throat is tighter than that of the 5.56 but will still function reliably with both 5.56 and .223 ammo.
If you are looking for a heavy barrel with some added weight, the Ballistic Advantage Barrel Hanson for the 5.56 or .223 round is a good choice.
This barrel has a 1:7 twist rate and a rust resistant QPQ corrosion exterior finish, as well as a high pressure and magnetic particle inspection to ensure that there are no flaws within it whatsoever.
The barrel has a nickel coated barrel with an M4 feed ramp to not only ensure proper reliability and feeding but proper extraction on the spent shell casings as well.
While Wilson Combat is mostly well known for their 1911 pistols, they also manufacture high quality AR-15 components as well.
This barrel is built out of 416R stainless steel to ensure good accuracy over the long term, and has a total weight of 32 ounces and M4 style feed ramps for reliable feeding.
All Wilson Combat AR-15 barrels are built to exact technical specifications using computer controlled equipment, and are also outfitted with hand polished feed ramps and bores to ensure that the new barrel will meet even the most demanding of expectations.
The Daniel Defense AR-15 barrel is built out of a cold hammer forged chromium molybdenum vanadium alloy steel so that it functions very similar to a match grade rifle barrel.
It also comes with M4 style feed ramps, and is available from 10.5 up to 16 inches in terms of barrel lengths.
The Daniel Defense AR-15 barrel also comes installed with a proven manganese phosphate finish to give it excellent resistance to moisture, corrosion, water, and surface wear.
The barrel is also available with both government and lightweight contours.
Last but certainly not least, the Criterion barrel for the .223 Wylde round has a 1:8 twist rate for excellent accuracy in addition to a chrome lined bore.
The gas ports have also been optimized for the respective barrel lengths, and the are available from carbine to mid length to rifle length gas systems as well.
The gas ports of this barrel are also optimized for each barrel length to ensure proper cycling and reliability.
It also comes installed with an M4 feed ramp to further ensure reliable feeding, and the barrel furthermore comes installed with a dimple that is opposite of the gas port for better performance.
Based on the information you have read in this article, you should now have an excellent idea of the different types of AR-15 barrels that are out there so you can choose the best barrel for you when assembling your own AR rifle.