The barrel on your AR 15 might be more important than you know. AR 15 barrels can determine a lot about your rifle. It optimizes the type of round the gun fires, the purpose, its effective range, durability, and even the legal status your gun occupies. There is a lot to talk about when it comes to barrels, and today, we are going to deep dive into the world of AR 15 barrels. We will talk about the inside, the outside, the length, weight, and beyond. Because there are so many calibers in the AR 15 world, we will have a bit of a focus on the 5.56/223 options. This information can apply to other calibers, but the focus is mostly on the 5.56 variants due to their extreme popularity.
The length of your barrel is essential for a few reasons. First and foremost, the length determines the legal status of your firearm. Without going too deep into firearms laws, AR 15 rifles must have barrels at least 16 inches in length to be rifles. Anything shorter results in a short-barreled rifle, which is an NFA firearm, or an AR pistol, or a firearm. That’s the legal line when it comes to barrel lengths.
From a practical perspective, the length of your barrel affects the velocity of your round. The 223 Remington and later the 5.56 NATO is designed to reach peak velocity from a 20-inch barrel. Optimal barrel length varies by round, and cartridges like the 300 Blackout can be optimized from a barrel as short as 9 inches. When choosing a cartridge and barrel, it pays to do some research in which barrel length will optimize the round.
That being said, trimming your barrel length to below optimal length does not render the weapon ineffective. 16-inch barrels are the most popular choice out there for the 5.56 cartridge, and it performs admirably from shorter barrels. The loss of velocity and increase in muzzle flash and concussion are notable, however. The shorter you get, the more blast and loss of velocity you’ll experience.
Longer barrels provide more velocity and generally a more comfortable shooting gun. Shorter barrels allow for more maneuverability and a lighter weight weapon overall. Longer barrels are excellent for long-range shooting, competitions, and hunting. Carbine and shorter length barrels are perfect for home defense and tactical applications. Finding a right balance for your needs is essential, and Bear Creek Arsenal offers barrel lengths from 4 to 24 inches in various calibers for your needs.
Barrel profiles refer to the thick and thin points of a barrel. Light and heavy barrels both have their benefits, and each is purpose-driven for specific rifles and purposes.
Lighter barrels are more ergonomic and more maneuverable. They make the weapon easier to quickly move with, to hold up for more extended periods, and to hike and hump during non gunfighting endeavors. Under sustained fire, they do start to heat up, and accuracy degrades.
A heavier barrel provides a more rigid and stable barrel for greater accuracy. Heavier barrels resist heat and allow for greater precision during sustained fire. The downside is the physics of heavier barrels. More weight slows you down and wears on you more.
Here are the most common ar barrel profiles:
Pencil thin barrels, also known as A1 profile, are thin and lightweight barrels. The pencil design is superbly light and perfect for quick snapshots, long hikes, and holding the weapon up for an extended period of time. The Pencil thin barrels aren’t great for long term sustained fire.
Government / M4
These two profiles are very closely related and differ slightly. [The Government] profile has a thin .625 inch barrel behind the gas block and .750 inch barrel in front of the barrel. This profile is used for the M16A2 barrel type. This barrel type was created to address a barrel bending problem that didn’t occur.The M4 barrel profile is similar but has a thin cut-out in the .750 portion of the barrel to accommodate an M203 grenade launcher. The Government profile is still popular because the M4 profile is still used, although it doesn’t offer much advantage besides extra barrel weight helping to deal with recoil.
Heavy barrels are designed to defeat the heat and enhance accuracy at the cost of more weight. Heavy barrels are popular on rifles built for extreme marksmanship and consistent fire. Heavy profiles can vary, but they are typically thick until near the barrel's end, where they taper towards the thinner side for balance. Heavy barrels are also popular with ultra-short AR 15 barrels. Weight is the primary downside of this profile.
Fluting a barrel involves strategically removing material in areas where it is not needed to reduce weight while maintaining a rigid barrel. A fluted barrel can often deliver benefits similar to, but not equal to, a heavy barrel without the weight. [See our blog post about the benefits of fluted barrels.]
4140 is excellent barrel steel that’s common in budget barrels. This barrel type is more than capable of acceptable accuracy with suitable ammunition. Match grade, they are not, but they are satisfactory for most shooting endeavors.
4150 contains slightly more carbon than 4140, and that little extra carbon makes 4150 barrels a little more robust for a longer barrel life and a little more accurate.
Chromoly Vanadium 4150
Chromoly Vanadium sounds like a synth-pop band, but alas, it’s a steel that delivers an excellent combination of strength and precision. It outperforms 4140 and standard 4150 at a slightly higher cost. This is the steel used in Colt M4 military rifles, and it’s well-proven. [Bear Creek Arsenal uses Chromoly Vanadium 4150 Steel in all their AR barrels with parkerized and black nitride finishes.]
If your goal is to build an absurdly accurate AR 15, then 416R is the steel to go with. Stainless steel enhances accuracy and resists heat better than other standard steels. Most shooters won’t need this type of barrel. 416R stainless steel barrels are designed for sub-MOA accuracy with match grade ammo, and their high price reflects that. [416R Stainless Steel is used in all of BCA’s stainless steel barrels.]
Twist rates are an interesting conversation to have, but you must realize exactly what we are discussing before we do. The twist rate refers to the rifling on the inside of the barrel. Rifling is a series of lands and grooves that rotate the projectile as it travels down the barrel. This rifling imparts spin on the projectile and stabilizes the bullet throughout its travel.
Twist rate is in reference to how often a projectile makes a complete rotation inside the barrel. Twist rate is usually expressed as a number like 1:7, 1:8, 1:12, and anything in-between, below, and beyond. The one stands for one complete rotation, the number after the one is how inches it requires for the round to make a complete rotation. So with a 1:8 twist rate, it takes 8 inches of barrel for the projectile to make a full rotation. The smaller the number on the right is, the faster the twist rate. 1:7 is faster than 1:12, for example.
Different twist rates exist not just for different calibers but for different bullet sizes. Stabilization is based on bullet length more than weight. Longer bullets are typically heavier bullets are require a fast twist rate to stabilize. In the AR 15 world, the most common heavyweight projectile is 77 grains. A 77 grain round is best stabilized by a 1:7 twist rate.
Lighter rounds like 55-grain spitzers can be stabilized by something as slow as a 1:12, but those are relatively uncommon. Most AR owners would be well served with anything in 1:7, 1:8, or 1:9 category. If budget based bulk ammo is your primary choice, then the 1:9 twist rate is quite versatile.
When choosing a barrel, consider your specific caliber, as well as your intended projectile weight.
Twist rates are one part of rifling to consider, but a second part is how the rifling is applied. There are two common types of rifling application, cut rifling and button rifling.
Cut rifling is a cool old school means to rifle a barrel. Cut rifling requires each individual cut to be applied by a single cutter. This slow process is incredibly measured and very precise. The end result is the forming of a supremely accurate rifle. Cut rifling is most commonly used in rifles designed to achieve a sub-MOA. It’s a lengthy, time-consuming process that demands a premium.
Button rifling is the most common type of rifling applied to modern rifles. It’s quick and very efficient for mass production and produces perfectly acceptable and downright good accuracy. A sizeable hydraulic barrel drives a mandrel through the barrel and leaves a rifled barrel behind. Button rifling works well for the vast majority of rifles.
Cold Hammer Forged
Cold hammer-forged barrels are created when a mandrel with the reverse imprint of the barrel’s rifling is beaten into a barrel blank. The hammers beat the heck out of the barrel around the mandrel. This forges the rifling on the inside of the barrel. The is taken off the mandrel, and your barrel is complete. Cold hammer-forged barrels are incredibly durable and provide an excellent degree of accuracy and durability under sustained fire.
Barrel treatment is the application applied to the inside and outside of the barrel. Barrels are exposed to intense heat and pressure and are prime candidates for rust. A good treatment helps expand barrel life and defeat common barrel ailments.
Chrome lining is an internal bore coating that is applied to the rifling, the chamber, and the bore. Chrome lining resists rust and ensures the inner barrel is nice and hard. Chrome lining remains a popular choice for manufacturers and is well proven.
Nitride treatment is a process of case hardening the barrel that hardens the steel and lends itself well to an incredibly durable barrel. To achieve this, the barrels are dipped into a combination of nitrogen, oxygen, and carbon that is heated to 1,600 degrees. This binds the chemicals to the steel. It also turns the steel a matte black that resists rust and common abrasions. Melonite is a commercial brand name for nitriding a barrel.
Parkerized is a commercial term for a barrel treatment that’s become popular enough that the name parkerized has become synonymous with manganese phosphate. Parkerizing uses a manganese element to create a treatment over the steel of the barrel. At the same time, it doesn’t make the steel as strong as nitride coating but is more affordable and more comfortable to apply.
A Barrel of Barrels
There is no perfect barrel choice that will work with every AR-type rifle. It’s a silly idea that there could be a perfect barrel for every AR rifle, pistol, or firearm. There are too many different designs and types to ever make that true.
That’s a good thing, by the way. This allows us to customize our AR to a specific task, and that’s an uncommon virtue for firearms. You can have a half dozen ARs designed for different purposes, and one of the biggest deciding factors in their purpose is their barrel lengths. Choosing the right barrel is a big choice, and hopefully, what we’ve discussed here today will lead you to the right barrel for your gun.