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Brownells – Changing An AR-15 Barrel

The transformation of an AR-15 barrel from a pre-banned configuration to a post-banned design is a meticulous process that requires careful execution. In “Brownells – Changing an AR-15 Barrel”, this detailed procedure is broken down step by step, from disassembling the barrel from the receiver to ensuring the final functionality test before firing.

Hosted by Brownells, Inc, this video is a part of an extensive showcase series dedicated to the AR15. Viewers gain a comprehensive understanding of not only how to achieve a configuration change, but also the anatomy and mechanics of their rifle. By the end of this instructional demonstration, you’ll be well-equipped and confident to modify your AR-15 barrel.

Brownells - Changing An AR-15 Barrel

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Table of Contents

Proper Preparation

In changing an AR-15 barrel from a pre-ban configuration to a post-ban one, the first step entails proper preparation. You’ll initially focus on removing existing components from your firearm.

Removing the Flash Suppressor

Commence by removing the flash suppressor, a device attached to the muzzle of a rifle that reduces the visible signature of the burning gases exiting the muzzle. This minimizes the chances of drawing attention to the shooter. Use a gunsmithing wrench or pliers to ensure proper disassembly without damaging the suppressor.

Removing the Sight Riser

After the flash suppressor, detach the sight riser. Take care to preserve this integral component of your AR-15’s sighting system, often needed for raising the height of flat-top rifles to allow usage of standard iron sights.

Disassembling Gas Block and Gas Tube

Once the sight riser has been carefully removed, your next step is to dismantle the gas block and the accompanying gas tube. The gas Block regulates the gas directed out of the barrel during firing, enabling the system to cycle and insert another round into the firearm’s chamber.

Removing the Forend

After the gas block and tube have been detached, proceed to remove the forend – the part of the rifle you hold on to when aiming your firearm. Its detachment will vary based on the type and model of the rifle.

Preparing the Nut with an Armorer’s Tool

With the forend removed, your next step involves using the armorer’s tool to loosen the barrel nut. These specialty tools are designed to provide the leverage needed to torque and untighten the barrel nut effectively.

Separating the Barrel from the Receiver

Having properly prepared your AR-15’s components, the next phase involves separating the barrel from the receiver – the part that houses the firearm’s operating parts.

Loosening the Nut

Valuable assistance from your armorer’s tool loosens and eventually disengages the barrel nut, thereby separating the barrel from the receiver.

Extracting the Delta Ring

Post-loosening of the nut, extract the Delta ring, a crucial part maintaining the forend of your AR-15.

Segregating Barrel and Barrel Nut Combination for the Post Ban Barrel

With the Delta ring out, segregate the barrel and its associated barrel nut. This process prepares for further assembly using the post-ban barrel.

Setting Up the New Barrel in the Receiver

The separated components will now pave way for setup of your new barrel in the receiver.

Getting Familiar with the Free Float Tube

The barrel you are setting in will likely have a free float tube, a type of handguard design that doesn’t touch the barrel beyond the upper receiver, mitigating any potential impact on barrel harmonics and increasing firearm accuracy.

Indexing the New Barrel in the Receiver

Once familiar with your barrel’s components, commence indexing the new barrel into the receiver. Remember to check alignment of parts for smooth assembly.

Understanding Function of Built-in Barrel Nut in the Rear of the Assembly

Overlooking the built-in barrel nut would be detrimental. Positioned at the rear of the assembly, it’s essential in securely holding the barrel to the receiver.

Thread alignment and Gapping

The barrel nut’s inside thread needs alignment with the receiver’s threads. Ensure this is done optimally, noting that improper thread gapping can severely affect your AR-15’s performance.

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Setting the Gas Tube and Torquing the Barrel Nut

Your new barrel will not be ready for use until you set the gas tube and properly tighten, or torque, the barrel nut.

Description of Ideal Gas Tube Alignment Operation

When it comes to the gas tube alignment, precision is key. The gas tube should ideally be aligned in a way that its bend is upwards.

Guidelines for Torque (30 to 80 Foot Pounds)

To ensure proper assembly, the barrel nut should be torqued between 30 and 80 foot-pounds. You might want to start at the minimum, steadily increasing the torque as needed.

How to Use a Torque Wrench and Armorer’s Tool for This Purpose

For an accurate torque application, use a torque wrench in conjunction with an armorer’s tool. Insert your backlash-free torque wrench into the armorer’s tool, making sure to set it at your desired foot-pound setting.

Checking of Gas Tube Alignment

Once the torque has been correctly applied, recheck the gas tube alignment. If it doesn’t line up perfectly, you can make necessary additional adjustments.

Further Adjustments to the Gas Tube and Barrel Nut

If the gas tube alignment was slightly off, further adjustments on the gas tube and the barrel nut can rectify the situation.

Increasing the Torque if Needed

In case the gas tube isn’t perfectly aligned, consider increasing the torque bit by bit. Ensure the gas tube port aligns exactly at the top.

Ensuring the Gas Tube Port is Exactly at the Top

Aim for the gas tube port to align at the top of the barrel nut, an alignment spot-on creates a conducive environment for optimal gas flow out of the barrel.

Checking and Achieving Alignment on the Gas Tube

Once you achieve perfect alignment at the top, you need to retain and secure it when attaching the handguard.

Attaching the Handguard on the New Barrel

The handguard’s attachment to your new barrel marks a significant step towards the completion of your task.

Keeping Control of the Gas Tube While Attaching the Handguard

While inserting the handguard, be cautious of the gas tube’s position; losing control might complicate your process.

Inserting the Front Sight Block onto the Gas Tube

Withe the handguard in place, the next step involves inserting the front sight block onto the gas tube. Be cautious during this insertion because losing control of it might lead to misalignment.

Use of Punches for Tighter Fitting

For a tighter fitting, make sure to use punches. This mechanical tool can help achieve an exact fit.

Achieving Snug Fit of Gas Block

Post the use of punches; you should aim for a snug fit of the gas block. This ensures the stability of your rifle during operation.

Securing the Gas Tube

With your gas block snug-fitted, your focus should now turn to secure the gas tube.

Removal from Vice and Use of Standard Gas Tube Pin

For this phase, start by removing your AR-15 from the vice. Then, insert a standard gas tube pin to secure the gas tube.

Use of a Small Hammer to Start the Pin

To insert the pin effectively, you might need the assistance of a small hammer. Gently tap the pin in to commence its placement.

Securing with a Cross Pin

Once the pin has started on its path, secure it with a cross pin. This ensures that the gas tube maintains its newly aligned position during use.

Final Adjustments and Levelling

Having secured your gas tube, the next step involves cross-verifying and honing of the alignment of the entire assembly.

Checking and Aligning the Front Sight with the Gas Block

You ought to ensure that the front sight is perfectly aligned with the gas block. Any misalignment can remarkably affect your firearm’s accuracy.

Locking Back to Blocks and Levelling

Once aligned, lock everything back into its place and ensure it’s levelled correctly. Both the receiver and the gas block should be on the same plane for optimal performance.

Application of Pressure on Screws to Lock in Place

Following successful levelling, use screws to lock everything in place securely. An appropriate amount of pressure should ensure that screws are adequately tight, securing your AR-15 barrel efficiently.

Testing for Proper Function

With your AR-15 barrel successfully assembled and locked in place, it’s important to test it for proper functionality before use.

Ensuring Smooth Bolt Closure on the Gas Tube

First, check to ensure the bolt closes smoothly on the gas tube. This indicates that your barrel change and alignment were successful.

Verification of Proper Movement

Next, verify the movement of the respective components. This often includes the bolt cycling and gas flow, which should function without any hitches.

Making Sure there is a Steady Gas Flow

Lastly, make sure that there is a steady gas flow from the gas tube. Proper gas flow is an indication of a well-assembled AR-15 and promises optimal operation.


Congratulations on changing your AR-15 barrel from a pre-ban configuration to a post-ban one. Highlighted steps include: proper preparation, separating the barrel from the receiver, setting up the new barrel in the receiver, adjusting the gas tube and the barrel nut, attaching the handguard on the new barrel, securing the gas tube, completing final adjustments, and testing the barrel for proper function.

Remember, correct alignment and snug fitting during assembly is not overrated. It ensures that your firearm operates efficiently, thereby enhancing its performance.

That said, don’t shy away from rigorous testing after assembly. Thorough testing is your assurance that your firearm will function as expected once put into operation. It’s also a good practice to ensure safety when handling and using an AR-15.

Enjoy safe usage of your AR-15, appreciating the smooth operation and improved accuracy brought about by your careful barrel change.

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