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The AR-15 Barrel

The AR-15 Barrel

October 10, 2018

As a future AR-15 owner, you need to know more about the rifle than the average joe. For most, the AR is a rifle you can shoot bullets out of. This is true. However, you need to know how the barrel chamber and the barrel function to make the most out of your rifle experience. Want to improve your accuracy? A new barrel could do the trick. It’s important to know why a new barrel could help. Want to shop other AR-15 accessories easily online? Shop Rail Scales now!

Barrel Chambering and Barrel

Before we dive into the actual barrels available to the AR, let’s discuss the barrel chambering component. This component is where the round sits after it’s been chambered and sits ready to be fired. The barrel chamber is the primary component that needs to be adjusted to accept the round being shot, as well as the barrel itself.

In this guide, we’ll focus more on the 5.56X45mm NATO round and the .223 Remington to keep thing simple. There is a wide selection of chamberings that the AR can fire, including:
  • .22LR
  • .50 Beowulf
  • .30 Varieties
What’s more, some barrels and chambers can fire more than one type of round. Here’s a general guide that you should confirm with various sources before firing any round from your rifle:
  • A 5.56 barrel can shoot both 5.56 and .223
  • A .223 barrel can only shoot .223
  • A hybrid chamber, for the most part, can shoot both

Barrel Length

When you think of barrel length for the AR, remember that “long is strong.” Here’s why: the bullet muzzle velocity (ft/sec) his higher with longer barrels. Granted, a longer barrel doesn’t mean more accuracy, but you do get more velocity out of a longer barrel.

As a side note, make sure and check with federal, state, and local regulations on barrel length. For the most part, barrels are required to be at least 16 inches in length. In some regions, states, and areas, the 16 inches can include attachments or the rifle. If the rifle is included in the length of the barrel, the barrel must be permanently attached. Finally, check regulations, because some states and counties do not allow any barrel less than 16 inches, whether attached or not.

Will you be shooting primarily at the range, or will you be out on a hunting lease stalking game? Remember, a shorter barrel is easier to move around with, but a longer barrel will give you more range (not necessarily more accuracy).

Barrel Twist Rate and Material

The twist rate of a barrel is denoted by the following ratio: 1 x number. For example, a 1x12 ratio means one twist per 12 inches. Generally, the longer the round, the faste the twist needs to be to fire. In other words, the shorter the length it takes to twist the bullet fully.

Keep in mind that the most common commercial barrel twist rate for the AR-15 across the industry is 1x9 at 55gr weight. Mil-spec twist is generally 1:7 since it needs to carry and stabilize heavier, longer rounds.

Moving onto the material, barrels come in a variety of types. Here are the general types of materials you can expect to find for AR-15 barrels:
  • Stainless Steel
  • Chrome Molybdenum Vanadium (CMV)
  • 4140
  • 4150
For most, the 4140 is a great choice. It’s lighter than the 4150, and it’ll last longer than the stainless steel with moderate shooting habits.

Barrel Lining

There are three primary kinds of barrel linings you will find:

  • Ferritic Nitrocarburizing (FNC)
  • Chrome Lined
  • None 
Depending on your shooting habits, barrel lining, and how you care for your barrel, you will find that you can shoot between 10-20 thousands rounds before needing to re-barrel.

Barrel Testing Marks

Manufacturers utilize the following acronyms to let you know the barrel has been tested a certain way:
  • Magnetic Particle (MP)
  • High Pressure (HP)
  • None

Barrel Forging and Contours

If you have your barrel forged, you will find that you can put more rounds through it before you need to re-barrel. With that being said, it’s important to understand that barrel forging, for the most part, reduces accuracy across the board.

Barrel contours on the other hand are simply the thickness and shape of a given barrel. Here are some general specifications for barrel contour:
  • Colt Automatic Rifle (CAR)
  • Bull (Heavy)
  • M4 or Government (Medium)
  • Pencil (Light)

Feed Ramps

The further we dive into the AR-15, the more you will find that there are dozens of specificities that you will need to know if you’re going to build your own rifle. This is why we suggest you buy your first one or two rifles to get familiar with how they work and function before building your own. Nonetheless, you want to check and make sure your ramp

Are you ready to chop online for AR-15 accessories? Buy from Rail Scales today!