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Upper Receiver Assembly


When handling firearms, always observe safety rules and the precautions set forth in the firearm's owner's guide. Be certain that your firearm is unloaded and made safe before proceeding with this DIY.









AR-15 Upper Receiver Assembly

Understanding how an AR-15’s upper receiver is assembled allows you to not only assemble a fully functional upper out of parts, but also gives you the knowledge to do preventive maintenance, to swap parts to keep your upper running right, or to customize your upper as you see fit.

With the current market being as hot as it is, many AR-15 enthusiasts are finding it increasingly difficult to find factory-assembled uppers available at the store. Although buying a complete upper from a reputable company comes with assurances that the quality and workmanship are all there — along with a great warranty in many cases — there is something to be said about building your own upper.


One of the advantages of rolling your own is selecting the exact specs and components you want. Another is gaining the experience and better understanding of how each part interacts with one another. Knowing how your gun operates can be as important as how to shoot it, as this insight can help you diagnose problems on your own, rather than relying on an armorer.


The AR-15’s upper receiver is where the bulk of the action occurs within the rifle. It is in the upper that accuracy and reliability are mostly determined. While there are many methods of assembling uppers that can make it quite an art form, we’ll leave all the tricks of the trade to the master gunsmiths. Within the scope of this article, our goal is to focus on the basics with this build.



We want you to get as much out of this guide as you can, so we went ahead and disassembled the Daniel Defense A4 Upper Receiver Assembly (100-005-851 / $139.99) that the upper will be built off of. We’re doing this in case you have a stripped receiver and upper parts kit that you need to put together.

To keep things easier to follow, let’s go about this in sections. Parts for each of the sections will be called out at the beginning of each section.

 I. Stripped Upper Receiver Assembly, II. Barrel, Gas System, and Handguard Assembly, III. Muzzle Device Timing, IV. Installing Bolt Carrier Group, Charging Handle, and Accessories, V. Function and Safety Inspection


There are a few basic specialized tools that you will need to properly assemble an upper receiver.

  1. 1. DPMS AR-15 Upper Receiver Block
  2. 2. Smith Enterprise .223 Armorer's Wrench
  3. 3. Loctite C5-A Antiseize Lubricant
  4. 4. Brownells® #3 Starter Roll Pin Punch
  5. 5. Brownells® Bench Block
  6. 6. Break Free CLP
  7. 7. 1/2-inch Torque Wrench
  8. 8. Vise
  9. 9. Hammer

I. Stripped Upper Receiver Assembly

II . Barrel, Gas System, and Handguard Assembly

III. Muzzle Device Timing

Go To Next Step

IV . Installing Bolt Carrier Group, Charging Handle, and Accessories

V. Function and Safety Inspection

AR-15 Upper Receiver Assembly

There you go; you now have an upper receiver assembly that you put together yourself. Attach it to a lower receiver and you’re ready for the range. Remember to keep the upper lubricated, especially during its first couple hundred rounds. Also don’t forget to double-check that any screws don’t come loose after your first outing with it.

With this newfound knowledge, you can now build, maintain, and modify an AR-15 upper receiver to your heart’s content. But please remember to follow all safety precautions and triple-check your work. Since we always love a dose of gun porn, share your creations with us and fellow readers on our Facebook page.