How To Build an AR-15 Rifle
Before you buy your first part, decide what kind of rifle you want. Will you be varmint hunting, plinking or competition shooting? Once you make this decision, you know what type of upper receiver and barrel you will use. The upper receiver and barrel you choose will determine the remaining parts needed.
Here are several types of stripped upper receivers, each with different features for different applications.
AR-15 A1 - Has a fixed carry handle, shell deflector and requires the installation of the forward assist assembly, ejection port cover assembly and the A1 sight assembly that allows only for windage adjustment. This upper is ideal to build a "Retro" civilian version of the Vietnam era M-16 Rifle..
AR-15 A2 - Has a fixed carry handle, shell deflector and requires the installation of the forward assist assembly, ejection port cover assembly and the A2 sight assembly that allows for windage and elevation adjustments. This is a popular upper to use for building a rifle for use in shooting matches.
AR-15 A3 - Has a flattop with picatinny rail, shell deflector and requires the installation of the forward assist assembly and ejection port cover assembly. This is the current military upper and is used to build a civilian copy of the M4 (carbine with 16" barrel) or M-16 A4 (rifle with 20" barrel). Also great for building any type of Varmint or Target Carbine/Rifle since any type of optic can be mounted to the Flattop.
AR-15 Flattop - Has many configurations for the upper receiver with various heights of picatinny rails for mounting scopes. These generally do not accommodate the forward assists or Ejection Port Cover assemblies or also known as the "Slick-Sided" uppers. The Flattop is great for building any type of Varmint or Target Carbine/Rifle since any type of optic can be mounted to the Flattop.
For your project, we decided to build a Varmint Rifle in 204 Ruger. Since we want to scope your rifle, we do not want an upper receiver with a carry handle, nor do we need open sights. That rules out the AR-15 A1 and A2. Therefore, either the AR-15 A3 or the Flattop will do. We chose the A3 because of its versatility. In addition, since we are building a Varmint Rifle designed for accuracy, we want to install a bull barrel with a free-float hand guard.Back to Top
Now that we have selected the type of upper receiver (A3), we know we need the forward assist assembly and Ejection Port Cover assembly. These parts would not be required had we selected a Flattop. In addition, since we are using a bull barrel with a free-float hand guard and without sights, we need a gas block but do not need a flash hider. Had we decided to use open sights, your front sight would have had the gas block built in. The free-float hand guard does not require the use of a delta pack or hand guard cap, as these are integral to the Free Float Tube hand guard.
Use our AR-15 Schematic for parts identificationBack to Top
Please remember these important things:
- Safety - Always remember to wear safety glasses. Pins and springs can (and probably will) fly across the room. A shop apron is also helpful to protect your clothing.
- Work Surface -Be sure to work in a well-lit area with plenty of clear, clean workbench area. Place a mat like the Tipton Gun Cleaning and Maintenance Mat over your work area to keep parts from rolling around or getting lost. The mat will also help protect your guns and parts from potential damage.
- Floor Area - Since we are working with several springs and small pins, it is likely some of these small parts will find their way to the floor. If you have a clean floor or even if you place a white towel or some plain covering on the floor, it will be easier to find these small parts. Nothing is more frustrating than having to delay your project because a $ 0.99 roll pin vanishes.
- Tools -There are several tools necessary to do a professional job. Please don't skimp here, as the quality of your work will suffer. Use the right tool for the job. Try to use brass punches whenever possible to reduce the chance of marring the finish.
Spread out your Tipton Cleaning and Maintenance Mat
- Arrange all your tools on your workbench so they are easy to access.
- Arrange all your parts on your mat.
- Group your parts together by assembly or with related parts. Refer to the pictures to aid you in this grouping process.
Install Forward Assist Assembly on Upper Receiver
- Forward Assist
- Forward Assist Spring
- Forward Assist (Roll) Pin.
*NOTE: If you take off the spring, you can see a flat side on the Forward Assist - this is where the pin rides.
Forward Assist Assembly is now installed.
Install Ejection Port Cover Assembly on Upper Receiver
- Ejection Port Cover
- Ejection Port Cover Pin
- Ejection Port Cover Pin Snap Ring
- Ejection Port Cover Spring.
Ejection Port Assembly is now installed.
Assemble the Bolt Carrier Assembly
The Bolt Carrier Assembly consists of:
- Bolt Carrier
- Bolt Cam Pin
- Firing Pin
- Firing Pin Retaining Pin
Test the bolt to make sure it moves in and out of the Bolt Carrier freely.
AR-15 Bolt Carrier Assembly is now Complete.
Assemble the Charging Handle Assembly
- Charging Handle
- Charging Handle Latch Spring
- Charging Handle Latch Roll Pin
- Charging Handle Latch
Install Charging Handle Assembly & Bolt Carrier Assembly into Upper Receiver
To complete the assembly of the Upper Receiver, you can go ahead and install these parts to ensure proper fit. However, you will have to remove these parts to continue with the installation of the Barrel Assembly.
Slide the Charging Handle Assembly in only far enough that it will stay stationary on its own.
Push the Bolt Carrier Assembly and Charging Handle Assembly into the Upper Receiver until they click firmly into place. The Ejection Port Assembly should pop open.
Installing the Upper Receiver into the Action Block and tightening it in the Vise
Install the Barrel
Install Outer Receiver Nut and Inner Barrel Retainer Nut on Barrel Threads
*Note that these instructions are recommended by the manufacturer of the Free Float Tube Handguard that we chose. If you are installing another type of handguard, instructions may vary.
- Outer Receiver Nut
- Inner Barrel Retainer Nut
- Free Float Tube Handguard
- Flat Head Handguard Screws (7)
- Handguard Plug Screws (7)
- Sling Swivel Studs (2)
Unscrew and seperate the Inner Barrel Retainer Nut from the Outer Receiver Nut.
Unscrew the Outer Receiver Nut past one full rotation, stopping when the gas hole on the Outer Receiver Nut is lined up with the gas hole on the Upper Receiver.
Tighten Inner Barrel Retainer Nut with Takedown Wrench until snug. Do not over tighten. If you are not using Loctite, make sure you hold onto the Outer Receiver Nut so the gas holes stay in alignment.
Seat the Threads (recommended in the U.S. Marine Corps Technical Manual). If you are not using Loctite, make sure you hold onto the Outer Receiver Nut so the gas holes stay in alignment.
- Torque to 35 ft-lbs
- Torque to 35 ft-lbs
- Torque past 35 ft-lbs until gas holes are in alignment, making sure not to exceed 80 lbs.
NOTE: With this particular handguard, if you cannot line up the gas holes within the torque range of 35-80 ft-lbs, loosen the Inner Barrel Retainer Nut and loosen the Outer Receiver Nut another full revolution and try again. You cannot do this if you used Loctite.
Remove Upper Assembly from Vise and Action Block.
Installing the AR-15 Gas Tube and Gas Block
This assembly consists of:
- Gas Tube
- Gas Block
- Gas Tube Roll Pin.
*Note: You may have to polish the Barrel where the Gas Block goes and polish the inside of the Gas Block with 600 grit paper so it easily slides in place. This only takes a minute or two.
Tighten set screws.
Drive Gas Tube Roll Pin through Gas Block and Gas Tube.
Install AR-15 Free Float Tube Handguard.
AR-15 Upper Receiver Assembly is now ready to be attached to your Lower Receiver Assembly.