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AR-15 Series: Brownells – How to Install an AR-15/M16 Trigger

In the realm of firearms, the AR-15 stands as one of the most well-regarded and popular choices due to its advanced design and user-friendly controls. However, one common point of criticism dovetails to the factory-standard trigger pull, often considered lacking. Our comprehensive guide offers detailed directives on substituting the factory trigger with an aftermarket fire control group, comprehensively designed to enhance your shooting experience and weapon control.

Prior to commencing this procedure, it is crucial to ensure your firearm is completely unloaded, with all possible ammunition sources removed from your workspace. The process necessitates specific tools, including a long screwdriver, a 5/32 inch punch, a nylon/brass hammer, safety glasses, and a Brownells AR-15 Lower Receiver Vise Block to secure your firearm during the installation process. The guide underscores key stages such as how to release the original fire control group, how to aptly position the new trigger, and vital checks to confirm correct installation.

Check out the AR-15 Series: Brownells – How to Install an AR-15/M16 Trigger here.

Table of Contents

Overview of the AR-15/M16 Trigger Installation

Installing a new trigger on your AR-15/M16 can greatly enhance your firearms performance, improving accuracy and operational consistency. While the thought of undertaking this task might seem intimidating, with the proper tools and a detailed step-by-step guide, it can be relatively simple. This article outlines the process that will help you tackle the task with ease and precision.

Understanding the Tools Needed

To begin, you’ll require a few specific tools to successfully install the AR-15/M16 trigger. These include a nylon hammer, roll pin punch set, safety glasses, a standard screwdriver, a receiver vise block, and a pivot pin detent installation tool. It’s crucial that you gather all these tools before you get started to ensure a smooth and seamless installation process.

Importance of Safety Measures

Safety is paramount. Always remember to treat your firearm as if it’s loaded, even when you know it isn’t. Before working on the firearm, check and double-check that it’s not loaded. Don’t forget to put on your safety glasses to protect your eyes against any potential flying debris. It’s important to conduct the entire process in a clean, well-lit, and clutter-free area to minimise risk and enhance efficiency.

Inspection of the Firearm Before Beginning

Before beginning the installation, conduct a thorough examination of the firearm. This will help you familiarize yourself with the layout and operation of the different elements, and allow you to identify any issues that might affect the installation of the new trigger. This initial inspection is important for ensuring a successful installation.

Preparation Before Installation

Ensuring the Firearm is Unloaded and Safe

First and foremost, before commencing any work on the firearm, ensure that it’s entirely unloaded. Confirm that the chamber is clear and that there’s no ammunition in the magazine or the receiver. This is an important safety step to prevent any accidental discharges.

Removing the Takedown and Pivot Pins

Once the firearm is fully unloaded and safe, proceed to remove the takedown and pivot pins. These pins link the upper receiver to the lower receiver. Ensure you keep track of these pins as they are essential for the reassembly of the firearm.

Separating the Upper Receiver

After the pins are removed, separate the upper receiver from the lower receiver. By doing this, you can easily access the internal components of the lower receiver, where the trigger mechanism is located.

Importance of the Brownells AR-15 Lower Receiver Vise Block

Making use of the lower receiver vise block is enormously beneficial in managing your firearm throughout the installation process. It assists in holding the receiver secure and steady as you work. The vise block effectively clamps into your gun’s magazine well, offering a stable platform and protecting the firearm from damage during the installation.

Removing the Pistol Grip

Loosening the Pistol Grip Screw

The next step is to loosen the pistol grip screw. This screw is typically located on the inside of the grip and can be accessed by turning the receiver upside down. Take note: the screw loosens counterclockwise and should be entirely removed.

Cautiously Removing the Pistol Grip

Once the screw is out, you can carefully remove the pistol grip, revealing the trigger assembly of the gun. Remember to handle this part with the utmost care as it also contains the detent and the spring for the safety selector switch.

Careful Handling of the Detent and its Spring

It’s vital to manage the detent and its spring carefully to prevent them from getting lost. After you carefully remove the pistol grip, remove and securely store the detent and spring. These small components are necessary for the proper functioning of the safety selector switch.

AR-15 Series: Brownells – How to Install an AR-15/M16 Trigger

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Removing the Fire Control Group

Inserting the Lower Receiver Vise Block

After you’ve safely stored the detent and spring, insert the lower receiver vise block. This allows you to safely and securely handle the lower receiver as you proceed with the installation.

Relieving Tension from the Hammer

Next, carefully relieve tension from the hammer. You should ensure that your thumb firmly holds the hammer to control its motion when you release the tension.

Tapping Out the Hammer Pin

With the tension relieved, you can then proceed to locate the hammer pin. Use the roll pin punch and the nylon hammer to carefully tap out the hammer pin. Pull the hammer up and out of the receiver and ensure the hammer spring is attached.

Removing the Trigger and Disconnector

Next, proceed to remove the trigger and disconnector. Use the roll pin punch to tap out the trigger pin. Carefully lift the trigger assembly out of the receiver. The disconnector should come out with the trigger because they share the same pin.

Introduction to the New Trigger

Orientation of the Trigger Spring

With the old fire control group removed, you can now introduce the new trigger. For a successful setup, ensure that the trigger spring is correctly oriented before you install it. The closed end of the spring should face forward and downward.

Preparation of USGI Triggers and Aftermarket Triggers

If you intend to use a Standard USGI Trigger, ensure you lubricate the disconnector where it touches the trigger. If you’re using an aftermarket trigger, the installation instructions provided should give proper guidance.

Fitting the Trigger Assembly Into the Lower Receiver

Slide the trigger assembly into the lower receiver with the trigger facing forward. Ensure the spring legs rest on the bottom of the receiver, and the disconnector spring is in place under the disconnector.

Installing the New Fire Control Group

Placement of the Hammer

After the trigger assembly has been put in place, follow up by installing the new hammer. Ensure the hammer spring is correctly installed and the legs of the spring are resting on the trigger pin.

Checking the Alignment of Pin Holes

Ensure the holes for the trigger and hammer pins align with those on the receiver. Misalignment may prevent the pins from seating correctly.

Use of the Nylon Hammer

Once everything is aligned, use a nylon hammer to start driving in the trigger and hammer pins. The nylon hammer prevents damage to the receiver and other components.

Ensuring Correct Settling of the Hammer Spring

Confirm that the hammer spring is correctly settled on the trigger pin for proper functioning of the fire control group. If not settled correctly, the hammer may fail to release when the trigger is pulled.

Testing the Functionality of the Installed Parts

Cocking the Hammer

Once you’ve successfully installed the fire control group, you will need to test the functionality of the installed parts. Cock the hammer and ensure it holds the position.

Checking the Hold and Release of the Trigger

With the hammer cocked, pull the trigger and see if it releases properly. If the hammer does not release, recheck the installation of the hammer and trigger springs.

Properly Sliding the Selector Into Place

Install the selector, ensuring it correctly slides into place. Note that the selector can only be installed with the hammer in the cocked position.

Carrying Out the Selector Function Test

Carry out a function test of the selector. The hammer should fall when you pull the trigger with the selector in the fire position and should not fall when it’s in the safe position.

Reinstalling the Pistol Grip

Insertion of the Detent and Spring

Once you’ve completed the selector function test, it’s time to reinstall the pistol grip. Start by inserting the detent and spring into their respective holes in the receiver.

Securing the Pistol Grip with the Screw

After placing the detent and spring, secure the pistol grip with the screw. Be cautious not to over-tighten the screw as this could damage the threads or the pistol grip.

Repeating Function Checks after Pistol Grip Reinstallation

After you’ve secured the grip, carry out function checks to ensure the safety selectors and trigger are working correctly.

Ensuring Safety After Installation

Attaching the Upper Receiver to the Lower Receiver

Reinstall the upper receiver onto the lower receiver and secure it in position with the pivot and takedown pins.

Elaborating on the Trigger Safety Measures

Safety is a top priority when using firearms. Focus on the safe handling of your firearm, taking care to always keep your finger away from the trigger until you are ready to fire.

Recommendation of Contacting the Manufacturer in Case of Any Concerns

If you notice any issues or have any difficulties, it’s crucial to contact the manufacturer or a certified gunsmith at the earliest. They can provide necessary support, specific instructions, and may even recommend servicing options if required.


Reflection on the Simplicity of the Installation Process

Installing a new trigger in your AR-15/M16 may initially seem daunting, but as you’ve learned in this guide, the process is straightforward and manageable when done with care and attention to detail.

Implication of the Need for Proper Safety Precautions

Despite the relative simplicity of the task, it’s important to remember that safety should always be your primary concern. Strict adherence to safety guidelines and practices ensures that the process is not only successful but also safe for you and those around you.

Appreciation of the Improved Factory Trigger Pull

With your new trigger installed, you’ll likely experience a significant improvement in your firearm’s trigger pull, thereby improving accuracy and overall functionality. This is just one of the many ways you can enhance your firearm’s performance and customize it to better suit your preferences and needs.

Check out the AR-15 Series: Brownells – How to Install an AR-15/M16 Trigger here.