Buying an AR-15 Barrel

AR-15 Barrel Questions

There are a lot of things that a person should ask themselves when getting a new AR-15 barrel. Two of the most important questions should be:

1. What am I going to use this rifle for?
2. How much do I want to spend on this AR-15 barrel.

These two questions should be at the core of buying your new AR-15 barrel. The reason for asking what you will be using the rifle for will have to do with the contour, twist, length, material, and rifling methods. This is the basics of how your barrel will look and shoot.
The second question is very straight forward. If you only want to spend a couple hundred dollars you will not be getting a custom barrel, but rather a mass produced rifle. This barrel will generally not be as accurate and most likely will not have specifics such as being fluted, having a custom contour, changing threading, and things of this nature. Let's begin with talking about lengths of barrels.

Barrel Rifling

There are three different methods to rifled barrels are made.  They are cut, buttoned, and cold hammer forged.  The basic difference between the three is that cut gives you much more versatility in groove size and depth and it takes a very skilled person to do this proficiently.  Cut rifling is my preferred method.
Buttoned rifling is not nearly as hard, but it is no versatile.  The groove size and depth are per-determined by the button and if you want to change this then you need another whole button.  This can be quite expensive to do.  This method also stresses the metal much more and needs to be relieved with finished.
Cold hammer forged rifling is a great method that a lot of people desire.  This method hammers the barrel blank into the correct rough shape.  The bore is smooth from this process as well.  The barrel does not have to be stress relieved since cold hammer forging works the metal from the outside in.  The density of the metal is also somewhat harder because of this forging process.  Cold hammer forging is advertised much more in Europe that it is in the United States as well. 

Barrel Materials

The AR-15 has several options for barrel material. The two that need to be mentioned are chrome-moly barrels and stainless steel barrels. Some people will tell you that one is better than the other, the fact is that it matters the application you will be using it for. In some instances one is better and in another set of instances the other is better.
One of the most popular steels is 4140 chrome-moly steel. This is the steel that is used in truck axles, bulldozer parts, and other heavy duty applications. These barrels can be parkerized or blued - although most AR-15's are parkerized. Chrome-moly barrels can also be chrome plated for corrosion resistance. The down-side to this is that chrome lining a barrel is a coating that is not uniform in thickness, so it effects accuracy. If you are doing short range - don't worry about it. Long ranges will be effected though. Another option is doing a nitride treatment. This is suppose to make it more corrosive resistant than chrome lining and increases the durability as well. This is a treatment so it changes the steel at a molecular level and not as a coating, hence it does not effect your accuracy.
And with stainless steel barrels a 416 stainless steel is used. This has a 10% chrome rating to help with corrosion, but it is generally not capable of being parkerized. There are options to make this barrel a little less noticeable. There is a black chrome kit from Caswell Plating - although it is a highly reflective black. There is also the DuraCoat option, and several color options. Ebay sells it several dollars cheaper than Amazon.com.
To sum it all up, stainless steel barrels resist heat and throat erosion better in general and can be lapped better. So, in general, they are more accurate barrels that hold up better. Chrome-moly barrels can be parkerized or blued to help resist corrosion as well as being chrome lined. With nitride treatments available now, this may become a completely mute point and chrome-moly may have a more durable and just as accurate future. For the everyday user, I would suggest a chrome-moly barrel that is chrome lined. For competition shooters and long range shooters stainless steel barrel and keep an eye on how nitride treatments progress.

AR-15 Barrel Length

The barrel length of any gun is important. The shorter a barrel is means that the bullet will be slower, weight will be less (in many cases), and maneuverability will be easier. There are some people who will tell you that shorter barrels decrease accuracy and this is as true as saying a longer barrel will improve accuracy - neither of them are true. Let's start at the front of this list and talk about a slower bullet.
If you took the same type of bullet and shot it from a 16 inch barrel and a 24 in barrel then you could see a difference in the feet per second. Average estimate would tell you that the 16 inch barrel would be moving somewhere between 200 to 260 feet per second slower than the 24 inch. Within reason, you will lose 25-30 feet per second for every inch you give up. But there are times that is may be important to give up a few inches. If you are shooting distance then you will want a longer barrel for the added feet per second.
In most cases, the shorter the barrel the lighter the barrel will be. If you have the same contour, or shape of barrel, then this will be true. But there are ways to modify this with fluting and what not. A heavier barrel is good for stationary shooting, bench shooting, etc. A lighter barrel is good if you are going to be walking all day, and there comes a time when a balance can be met. But that balance needs to be found for each person. Also, a heavier barrel will help reduce recoil. When the gun discharges the more weight there is the more energy is absorbed to move it.
We hit on the maneuverability a little in the previous paragraph. But a shorter barrel allows you to turn corners tighter and maneuver in tight quarters more readily. In combat situations this is a benefit. The USGI (United States Government Issue) M4 barrel is 14.5 inches in length to cut down on weight and to allow easier handling in combat situations. A 50 caliber Barrett M107 has a 29 inch barrel, this is a sniper rifle if you are not familiar with it. M4 a soldier will clear a building with, but the M107 is much too heavy to try to clear a building with.
Okay, let's clear up a myth about barrel length determining accuracy. This is not true what-so-ever. An AR-15 barrel has various contours or profiles. The heavier ones are more rigid than the lighter ones, in most instances. If you are shooting a 6.5 Grendel with a 28 inch light weight barrel, your accuracy is going to be very poor because of the flex on the barrel. But if you went with a 24 inch with an Heavy Barrel (HBar) contour, the barrel would be much more rigid and you would not get the flex that throws the bullet off target. With that let's move onto contours.

 

AR-15 Barrel Twist

Twist is the distance it takes to complete one rotate. My .17 Remington will have a 1 in 9 twist, also stated 1:9 twist. This means that it takes 9 inches for the bullet to complete one rotation. The higher grain the bullet the faster rate of twist. This is because a larger bullet has more weight and the twist helps it stabilize easier. The lighter and longer the bullet the harder it is to stabilize the round. With the .17 Remington I am planning to shoot 25 to 30 grain bullets. Generally, the .17 Remington is a 1:10 twist and people seem to use a 20 to 25 grain bullet.
Once reference that I have seen several places is George Greenhill's formula for finding a twist that stabilizes. The formula is in the blue box to the right, but it doesn't work with many bullets used today. The formula was created in 1879 and was meant for solid lead bullets that were of a higher caliber. This formula does not work with anything smaller than a 30 caliber.
One great place for finding theoretical twist is at JBM Ballistics. With this application you can input your caliber, the grain of the bullet, the velocity, temperature, bullet length, pressure, and twist and it will output the stability rating. You will want to be as close to the number 1. You do not to be less than one, but over one while being as close to it as possible.

                                                                 Common Contours

AR-15 Barrel Contours

There are quite a few contours, or profiles, for AR-15 barrels. To the right, I have posted some of the most common. As stated in the last section, some of the barrels have less material on the barrel. This makes them more flexible and in some instances less accurate.
At this point you know what caliber you will be shooting. And to help you decide what contour, you should think about the ranges you will be shooting, the accuracy you need, as well as how much weight you will be wanting to carry around. Maybe I should say, how much weight you are willing to carry around.
When it comes to the AR-15 rifle profile, it is highly dependent on what you are going to be using the rifle for. For example, there is an M4 contour that is 14.5 inches in length and it is wider at the butt and muzzle while slimmed down in the middle. This is to assist in making the rifle lighter for troops to carry all day. They do make the "M4" in 16 inch now for civilians, this is not a true M4 contour - but it copies the shape and follows the law.
It is my opinion, that it is always better to use a heavier barrel if you are unsure. I prefer accuracy and the heavier barrel gives more weight forward and cuts barrel whip down. Barrel whip makes the rifle have a wider grouping and the forward weight helps the shooter keep the rifle steadier.
There are many resources online if you are unsure. Or call one of the barrel makers and inform them of what you are doing and ask some advice. The people I deal with are great guys - although they are very busy. Because of this emailing can be better for some. My advice would be to be patient, to the point, and research what you are asking about.

The cost of your AR-15 barrel

It will take some looking to get a factory barrel that suits you. They have predetermined twist, length, and everything else. In this case you will need to make priorities of what is important to you and try to find that barrel. You may purchase barrels from a couple hundred dollars to five hundred dollars pretty easily.
Now, if you want a custom barrel. Take notes on what you will be using it for, what grain bullets you will be shooting, how long you will be shooting and figure out the caliber that will suit you the best. Then call several barrel makers, ask them questions and see who you are most at ease with. And who is available to make the barrel for you. I had two barrel makers in mind for making my .17 Remington. One of them is so far back logged that they politely refused new work, and the other is 90 - 120 days back logged. While talking to them the one still taking work was managing his time better and more organized. And talking to him, I was very impressed with his knowledge and put at ease that I would be having him custom make a barrel for me. For a custom .17 Remington, bolt and carriage, and truing the barrel and upper for me it will be somewhere around $500.00. The barrel maker I am having make the barrel has a great reputation and a reputation for making uppers that are quite capable of 0.5 inch groupings.

Your AR's purpose

Overall, the most important question will be, "What will I use my AR for?" You do not want to use a 6.5 Grendel for shooting birds nor do you want to use a .22 LR for shooting moose. If cost is an issue, then make sure to take into account how much ammunition is as well. A .22LR is around 5¢ while a .338 Lapua round is around $3.00 per. This is quite the difference in price here. Think long and hard about your AR's purpose before purchasing a barrel and make it a great purchase for a long time to come. Have fun and safe shooting.