AR Barrels – The First Decision

Why is the Barrel Choice of an AR so Important?

The AR Barrel is probably the single most significant change that you can make to the rifle itself. The barrel determines overall accuracy, range, caliber, and length of the weapon. It also directly affects the weight of the rifle and its maneuverability in tight spaces.

The very first thing that determines which Barrel is appropriate for you is determining how you are going to use the AR. A few common uses are hunting, long range shooting competitions, speed shooting competitions, home defense, and as a service weapon by either the police or military, which brings in additional aspects such as close quarters or sniper needs.

The choice of which barrel is correct for you includes considering things such as cost, the caliber round fired, barrel material, coating, length, and number of rounds you plan to shoot. Once those are determined you can fine tune your options even more by adding in things such as barrel twist rate, the gas system, muzzle threads, and any fluting or contours that will affect the cooling of the weapon.

Now let us break these choices down a bit more.

The Common Uses of an AR Style Rifle

The Hunting AR

When selecting options for an AR that you plan to hunt with your choices are a little greater. Your accuracy does not have to be quite as good as someone who is competing in shooting competitions. You are also not generally trying to maneuver the weapon around in very tight confined spaces.

Because of these less restricting factors, you mainly need to consider an appropriate caliber for the type of animal you are hunting. For animals smaller than deer, you can use the default .223 of 5.56 that most ARs are chambered in.

Some states allow you to use these calibers on Deer as well though, while some states indicate the power is insufficient for larger game. Another thing to point out is that the longer barrel weight allows for quicker follow up shots on the same target. Additionally, a longer barrel is most often more accurate.

The Competition AR

The competition AR depends largely on the types of competition that you are interested in.

Some choose shorter 14.5 inch barrels made from lightweight material so that they can quickly transition from target to target, though they sometimes have difficulty at longer ranges.

While other shooters prefer an 18 inch barrel that allows maximum accuracy at longer ranges. In these cases, they are not as concerned about the weight. Caliber is also a consideration here as well since some competitions specify specific ammunition.

The Home Defense AR

The home defense AR can be any AR you have at hand. However, if you are building one specifically for their purpose then a shorter barreled option with a suppressor may be the way to go.

An AR excels at Home Defense due to its large magazine capacity, low recoil, and quick time on target if using a site such as a RedDot. The main drawback to an AR is the volume of noise produced when an AR is fired inside. By having a suppressor you reduce this noise.

As in the other two examples caliber can play a big factor in your decision as well. Smaller calibers such as a 9mm pistol round may be appropriate in this case and could potentially reduce some over-penetration issues, while some may feel that a larger caliber is more likely to bring down an assailant quicker.

The AR as a Duty Weapon

Selecting the proper equipment for a duty weapon AR will often be at the discretion of an employing agency. However, if you are making the choices then it is important to consider your primary mission and the scenarios in which you will be deploying the AR weapon system.

Will you be inside most of the time, then a shorter barrel is more appropriate, will you be facing relatively short-range engagements at fewer than 200 yards if so then the shorter barrel is Ideal. Even the military’s primary choice of the M4 Carbine comes in with a 14.5 inch barrel. If you are intending to be more of a sharpshooter or sniper then longer barrels may be more appropriate.

Keep in mind things such as how much you will be carrying the weapon as well as if you will be getting in and out of a vehicle frequently.

The Barrel Options

The three most common characteristics of a Barrel are the length, material it is made from and the caliber it is chambered to fire. After that comes the thickness of the barrel, the design such as cooling flutes etc, finishes and the number of twists in the Barrel.

Barrel Length

The length of a barrel largely determines the accuracy of the rifle at longer ranges. Longer and heavier barrels tend to improve your accuracy while shorter barrels increase mobility and ease of carry while sacrificing some of your accuracy.

In order to avoid short barreled rifle issues you need to ensure you are using at a minimum 16 inches total barrel length. The exception to this is if you have a 14.5 inch with a welded on muzzle device such as a flash suppressor, muzzle brake or compensator that brings the total length to 16 inches.

There is no legal limit for the maximum length but most people opt for 16, 18 or 20-inch barrels with a few opting for 24 or 26-inch barrels. Keep in mind that you need to keep the overall length of the weapon twenty five inches or more unless you are going for a Short Barreled Rifle (SBR) which will require special tax stamps and comes with quite a few restrictions.

Barrel Material

The choices in a barrel material are primarily Carbon Steel and Stainless Steel. There are several types of steel involved in each of these but for most people the choice is simply between carbon or stainless. 

Carbon steels tend to be somewhat cheaper but are often chrome lined to prevent rust. This makes them resistant to corrosion, last longer and they tend to be easier to clean. However, due to the way the chrome is applied to the inside of the barrel minor imperfections can slightly reduce accuracy at long ranges.

Do not get that wrong though they can still be very accurate, they just are not generally considered competition grade. There are several types of steel used to make barrels with one of the more popular ones being chromium-molybdenum-vanadium or (CMV).

Stainless Steel barrels rely on their steel in order to remain rust free. They tend to cost a bit more, but are considered to be the best choice when maximum accuracy is desired. They also tend to wear out a bit faster than their carbon steel counterparts. Stainless Steel barrels are usually the first choice of competition shooters. 

Barrel Calibers

AR style weapons are available in nearly any caliber. The original AR platform was the AR10 and came chambered in the 7.62X51 Nato round. However, it was decided that a lighter weapon and caliber was needed so the AR15 was introduced. It was originally chambered in 5.56×45 Nato.

This quickly became the standard and was employed by the US Military as well as many others. Since that time additional calibers have been introduced. These include several pistol rounds as well as special barrels made to fit the .50 BMG round.

When selecting the caliber for your weapon how you plan to use it plays a large part. If you just want something you can take to the range to play around with or shoot small animals such as squirrels then you can get one chambered in .22LR. This would allow you to buy cheap ammo in bulk.

If you want a hunting rifle for deer then perhaps a .300 blackout or even a 308. One of the new players in this area is the 6.5 Creedmore which looks very promising.

The Barrel Finish

While it may seem that this is not a very important decision it can affect the upkeep and durability or your rifle barrel.

Most military rifles and many civilian AR are finished with a technique called Parkerizing. This type of finish is extremely durable and has been used by the US Military for over 50 years. It does require a light coating of oil to ensure its protective abilities though.

Chrome lining is nearly always desired on a carbon steel barrel. This lining makes the barrel very durable and resistant to heat. It is also much easier to clean due to the non-porous nature. There are some complaints that this lining reduces accuracy. Though that reduction tends to be at or just less than a .25 of an inch at 100 yards. 

The final of the three main treatments available at this time is a treatment with Nitride. This may appear as a nitrided barrel or a melonite barrel. This finish absorbs into both the inside and outside of the barrel. It is both very hard and very durable, with no requirements of lubrication to maintain its protective qualities. It also increases the hardness or the metal to around a 60 rockwell score as opposed to the typical gun barrel steel which is around 28 to 32 on the hardness scale. 

Single Shot and Magazine Capacity

This is a big factor in some states that have very limited magazine capacities.

For instance Georgia does not have any restrictions on magazine capacities in respect to rifles but other states such as California, Colorado, Connecticut, Maryland, Massachusetts, New Jersey, New York, and Vermont all ban high capacity magazines and you are limited to ten or fifteen rounds depending on the state.

There are some bolt action AR rifles as well, though these usually tend to be the much larger calibers such as the .50 BMG.

Make sure before you order any magazines that you are in compliance with your local laws. In order to better assist you with this I am compiling a list HERE that will lay these restrictions out. (The article is not begun yet but you can access the hunting regulations for each state at that location as well.) 

Barrel Twist and How it Affects the Round

The barrel twist is the small grooves cut inside of the barrel which cause the round to spin when it is fired. This both stabilizes the round and improves its accuracy and range. Think throwing a football. When it’s a good throw it spins and goes much further than when it flips end over end.

For an AR barrel, twist rates are listed as 1:7 or 1:9. The 1 refers to a full rotation of the bullet, while the second number tells you how many inches the round will travel in the barrel length before it completes that one full rotation. For example, with a 1:7 twist, the bullet needs to travel 7 inches before it completes one full rotation. In a 1:9 twist, it is 9 inches to achieve that full rotation.

For most purposes the heavier the round you plan to shoot the faster twist you want. AR barrels almost exclusively come in either 1:7, 1:8 or 1:9. The current Milspec is 1:7 and works fine for the 62 grain M855 5.56 round. Though it may start to cause some issues if using a  lighter 55 grain round in a long barrel. 

Due to these specs a 1:8 barrel is often the preferred choice and should give you decent results with rounds between 40 and 80 grains. It can use slightly heavier rounds than this as well though not with optimal performance.

The Gas Tube and its Length

While not actually part of the barrel the length of the barrel will determine your gas tube length. When an AR fires the build up in pressure is vented through a small hole in the barrel. At that point it enters the gas tube. There it is channeled back into the receiver. The build up in pressure then causes the rifle to cycle and ejects the spent round. If the channeled pressure is insufficient then the rifle may jam.

Gas Tubes generally come in three lengths which are often classified as rifle, mid length and carbine. Generally the longer the tube the more reliable the weapon is. The rifle length is normally used on weapons with a barrel length of twenty inches or more. The mid length is usually found on those barrels between fourteen and twenty inches. Last the carbine length gas tube is most common on barrels that are ten to eighteen inches in length. 

While there is no right or wrong in this area, most opt for either the carbine due its compact size or the mid length as it is a nice middle ground between the three. 

The Barrel Profile – How Shape Affects Your Experience

Your barrel profile will depend partly on choice and partly on your intended use. The barrel profile is the outer shape of the barrel. The options of this particular choice are nearly limitless. Profiles come in slim pencil shaped barrels or barrels that are thicker on one end then the other. You can also get a barrel that is very thick for the full length.

In addition to these basic options several companies offer their own specific contours. Each of these may or may not have advantages of their own.

Thinner barrels while being lighter and easier to maneuver may suffer from barrel whip. Barrel whip is the potential flex in the barrel when it is fired. This could cause some accuracy issues with very long thin barrels. At the same time, a thicker barrel would reduce this but could drastically increase the weight of the rifle. 

One of the more popular methods to deal with barrel whip is to use a fluted barrel. These barrels are thicker than a slim barrel but have small grooves of metal cut out of them. This increases their overall surface area allowing them to cool faster while still providing enough support to negate barrel whip. Reducing the temperature of the barrel will help you maintain your long range accuracy if firing multiple shots.

Muzzle Threads – Why do They Matter?

Muzzle threads are not necessarily required and you can select a barrel that is rounded similar to a handgun barrel. However, if you wish to add a suppressor, muzzle brake, or compensator then you will likely want to make sure you have a threaded barrel.

Most AR models can be had with a 1/2×28 thread base. This translates into the outer diameter being ½’ thick with 28 threads per inch.

That being said you can find both barrels and brakes, compensators etc in varying thread pitches and sizes. Make sure you consider this during your purchase if you plan on adding one of these devices.