How to Assemble an AR-15 Lower- A Step-by-Step Guide to Building Your Own Firearm

How to Build an AR-15 Lower

Building an AR-15 lower is a rewarding and exciting project for gun enthusiasts and DIYers alike. It allows you to customize your firearm and gain a deeper understanding of its mechanics. In this article, we will guide you through the process of building an AR-15 lower, from selecting the right parts to assembling them. Whether you’re a beginner or an experienced builder, follow these steps to create your very own AR-15 lower.

1. Gather the Necessary Tools and Materials

Before starting the build, ensure you have all the necessary tools and materials. This includes a drill press, a vise, a hammer, a punch, a file, a screwdriver, a torque wrench, and a cleaning kit. Additionally, you’ll need the following parts:

– Lower receiver blank or a stripped lower receiver
– Firearm safety actuator (FSA)
– Trigger and hammer
– Buffer tube and spring
– Pistol grip
– Stock
– Magazine catch
– Bolt catch
– Bolt carrier group (BCG)
– Gas key
– Firing pin
– Spring guide
– Bolt
– Buffer
– Buffer retainer
– Magazine

2. Prepare the Lower Receiver

Begin by cleaning and degreasing the lower receiver. This will ensure a smooth and reliable build. If you’re starting with a stripped lower receiver, install the FSA and ensure it’s properly secured. For a lower receiver blank, you’ll need to drill and tap the holes for the magazine catch, bolt catch, and safety selector.

3. Install the Firearm Safety Actuator (FSA)

Place the FSA in the receiver and secure it with the appropriate screws. Ensure the FSA is aligned with the safety selector and the magazine catch hole.

4. Install the Trigger and Hammer

Insert the trigger and hammer into the receiver, making sure they are properly aligned. Secure them with the necessary screws and check the trigger pull weight to ensure it meets your requirements.

5. Install the Buffer Tube and Spring

Attach the buffer tube and spring to the receiver. This will provide the necessary support for the BCG and reduce felt recoil. Ensure the buffer tube is securely attached and the spring is properly tensioned.

6. Install the Pistol Grip and Stock

Mount the pistol grip and stock to the receiver. These components will affect your shooting position and comfort, so choose one that suits your preferences.

7. Install the Magazine Catch and Bolt Catch

Attach the magazine catch and bolt catch to the receiver. These components will allow you to load and unload your firearm easily.

8. Install the Bolt Carrier Group (BCG)

Insert the BCG into the receiver, ensuring the gas key is properly seated. Secure the BCG with the appropriate screws and check for proper function.

9. Install the Gas Key and Firing Pin

Install the gas key and firing pin. The gas key will allow the BCG to cycle properly, while the firing pin ensures the hammer strikes the primer.

10. Install the Spring Guide and Bolt

Attach the spring guide and bolt to the BCG. These components will help guide the bolt during the firing cycle.

11. Test Your Build

After completing the assembly, test your AR-15 lower by cycling the action, loading a magazine, and firing a few rounds. Ensure everything is functioning correctly and there are no issues with the trigger pull, magazine release, or bolt operation.

Congratulations! You’ve successfully built an AR-15 lower. With this foundation, you can now proceed to build the upper receiver and complete your custom firearm. Happy building!