Install An AR-15 Barrel And Gas Tube

How To Install An AR-15 Barrel And Gas Tube?

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AR-15 Barrel Installation

There are numerous tasks in building an AR-15 which are different in complexity and mechanical know-how. This can be as small as basic plumbing too as complicated as an engine repair. There is a wide range of tools and techniques that are needed to complete the job. It may look easy on the surface, but it can turn out to be one of the most intricate processes.

One of the tasks includes fitting in a new barrel, the pipe with a collar. There are various reasons why one may need to install a new barrel. Either when building a new AR-15 or after the existing one is worn out after a lot of shooting. One may also decide to let a skilled gunsmith replace the barrel for them or do the work themselves. Whichever way, this process has three main steps. The following are the essential parts of any AR-15 Barrel install.

Step 1: Shop Essentials

The first and foremost item is the tool that is used to check alignment on a gas tube. Most times, this one is deemed unimportant and is often overlooked. It can be built bit by bit or bought ready-made. Going by measurements, it normally has a 0.118-inch diameter that replicates the gas tube and fits into the carrier key. One can also create one from a 4-inch section cut from an old glass tube without the ends. Another essential tool is a fixture which will serve to secure the upper component, also known as the upper receiver. One recommended fixture is the block style because they maintain access to the inner part of the upper receiver to check gas tube alignment.

Lubricant is essential, especially copper-based, that helps to prevent galling. This is where abrasive wear happens as a result of friction when metals that are in contact are put into motion against each other. With enough compression, this friction can generate heat that is hot enough to weld the metal surfaces together. This leads to more undesirable complications. Another option for a lubricant is white lithium grease which is not a hi-pressure lube so it may not withstand the heat. However, Aeroshell MS33 is also recommended.

AR-15 Barrel Installation
AR-15 Barrel Installation

Step 2: Installation

Installing a barrel extension may need a few specialized tools, but it is not a difficult procedure. It is important to clean all involved surfaces, both inside and outside the barrel. After this, the barrel extension is slipped into the upper part of the receiver. Using a flat brush, anti-seize is put around the surface of the upper threads.

This anti-seize allows one to tighten the nut down. The use of anti-seize that has graphite is not recommended, since it is likely to react with the aluminum metal and end up corroding the upper receiver. A torque wrench comes into use at this level to ensure that the USGI-pattern nut is in place. It may vary from a minimum of 30 ft-lbs to a maximum torque of 80 ft-lbs.

Important considerations to improve accuracy include how the well-greased barrel extension fits inside the upper receiver. Also, lapping the face of the upper receiver and the barrel is significant in the overall outcome. The barrel extension should be completely snug to the upper receiver. The outcome depends on the barrel and receiver being in good condition too to ensure the fit is not loose.

Step 3: Align the Gas Tube

This is one critical step that highly determines the precision and performance of the AR-15 in question. The USGI-pattern nut often has an opening on it which should alight perfectly with the gas tube receptacle. This is crucial and therefore, right at this step is where the aforementioned tool that assists with the alignment of the gas tube and the nut opening comes in. The tool is inserted in the carrier key and put into the upper.

After this, a test is carried out to make sure that the gas tube can rattle, that is, move freely in all directions. This is enabled by a 360-degree gap around the tube when the alignment tool is fitted in. This free movement is key because any contact in the gas tube has the potential to displace the carrier. It matters if one is pursuing high levels of precision.


Can you customize an AR-15 barrel? Totally, just like any other component of the AR-15 variety, depending on one’s desired level of performance. These are practical general-purpose instructions that are useful for any basic assembly involving the AR-15 barrel.

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