How To Build An AR-15 Upper Receiver: Step-By-Step Instruction

For AR-15 enthusiasts, building an AR-15 from scratch offers a sense of achievement and customization that purchasing off-the-shelf simply can’t match. I remember the first AR-15 upper receiver I assembled – it took me five hours and gave me the majority of the grey hair I have today, but man, was it a satisfying and rewarding experience!

So, are you ready to build your own AR-15 upper receiver? First, we’ll discuss whether it’s better to buy a complete upper or build your own, as both have their unique benefits. After covering the build instructions, we’ll also look into why it’s important to be meticulous when building your AR-15 upper, as it can significantly impact your build quality.

How To Decide Between Buying Complete Upper vs Building AR-15 Upper?

You should consider the main benefit of each when deciding between buying a complete Upper vs. Building your own AR-15.

When you buy a complete AR-15, like our editor’s pick, the Daniel Defense DDM4v7 16″, from the article – the best AR-15 upper receivers, you have the luxury of gaining access to a plug-and-play solution. Quality is also guaranteed, and you don’t need any special tools or skills. This is why we at HuntersHalt often recommend novice AR-15 enthusiasts buy a complete upper instead of building one.

However, there are a lot of benefits to building your own. For starters, it offers you a completely customizable experience – something you prefer as you become a die-hard AR-15 fan.

Additionally, building your own AR-15 upper tends to be more cost-effective than buying a complete upper unless you only buy premium individual parts. Finally, building your own AR-15 allows you to gain a deeper understanding of the weapon’s mechanics as you follow along with the AR-15 build instructions.

AR-15 Upper Build Instructions

There are eight steps you need to follow when building your own AR-15 upper.

1. Gather Equipment.
2. Install the Barrel.
3. Install the Gas Block and Gas Tube.
4. Install the Handguard.
5. Install the Muzzle Device.
6. Install the Charging Handle and Bolt Carrier Group.
7. Check Headspacing (Very Important!).
8. Final Inspection.

1. Gather Equipment

Before you start, ensure you have the following equipment:

• Vise and AR-15 vise block
• Headspacing gauges
• Torque wrench (for tightening the screws)
• AR-15 armorer’s tool
• Brass or nylon hammer
• Punch set

2. Install the Barrel

The barrel is the first part we install.

1. First, secure the upper receiver in your vise using the AR-15 vise block. Ensure it is nice and tight to prevent injury or damage to the parts.
2. Slide the barrel into the front of the upper receiver, ensuring the pin on the barrel aligns with the slot in the receiver.
3. Slide the barrel nut over the barrel and thread it onto the receiver.
4. Use your torque wrench and armorer’s tool to tighten the barrel nut to the manufacturer’s recommended torque – very important to double-check the manufacturer’s recommended torque, preventing a possibly stripped upper receiver or screws.

3. Install the Gas Block and Gas Tube

1. Align your AR-15’s gas block with the gas tube hole on the top of the barrel.
2. Slide the gas tube into the adjustable gas block, ensuring the pinhole in the tube aligns with the hole in the gas block.
3. Secure the gas tube with the roll pin using your punch set and hammer.
4. Secure the gas block to the barrel with the provided set screws or roll pin, ensuring your gas system is tightly secured to the barrel. Also, double-check that your gas port is open and clear, allowing sufficient controlled escape of gas when firing the AR-15.

4. Install the Handguard

1. It is very important that you first identify the type of AR-15 you have, as it will determine how you attach it to the rest of the AR-15. For instance, if your handguard utilizes the barrel nut for attachment (like many free-floating handguards), ensure that the barrel nut is compatible and properly oriented for your specific handguard model.
2. Next, gently slide the handguard over the barrel and align it with the upper receiver and barrel nut.
3. Secure the handguard in place according to the manufacturer’s instructions. This may involve tightening screws or using specialized clamps. Some AR-15s utilize a snap ring to secure the delta ring assembly to the barrel nuts – just follow the manufacturer’s instructions on how to secure it properly.

5. Install the Muzzle Device

1. Thread the muzzle device – flash suppressor or muzzle brake – onto the threaded end of the barrel.
2. Hand-tighten the device until it’s snug.
3. Using a wrench, tighten the muzzle device while ensuring it’s properly aligned. If the device has a specific top (like many brakes), ensure it’s oriented correctly.
4. Very Important: If your muzzle devices require it, don’t forget to install a crush washer before the device itself.

6. Install the Charging Handle and Bolt Carrier Group

1. First, you want to pull back on the latch of the charging handle and slide it into the upper receiver’s rear. Make sure the handle’s top side fits into the channel.
2. Next, insert the bolt carrier group (BCG) into the charging handle, ensuring the gas key slides smoothly into the channel on the underside of the charging handle.
3. Push both the charging handle and bolt carrier group forward into the upper receiver until they lock into place. Be careful not to damage the forward assist if your AR-15 has one when installing the charging handle – the button will be located right below the charging handle.

7. Check Headspacing (Very Important!)

1. Insert the appropriate headspacing gauge into the chamber – use your Daniel Defense manufacturer’s instructions to guide you.
2. Try to close the bolt on the gauge. If the bolt doesn’t close on a “Go” gauge and does close on a “No-Go” gauge, your rifle is safe to fire. Very Important: If the opposite occurs or if it closes on both, consult a professional gunsmith before continuing the build.

8. Final Inspection

1. Ensure all parts are securely installed, and there are no obstructions in the barrel.
2. Perform a function check: Charge the weapon using the charging handle, ensure the bolt moves freely, and that the bolt locks back after being charged.
3. Congratulations! If all checks are successful, your upper receiver build is complete.

Note: Always refer to the manufacturer’s instructions and specifications when building your AR-15 upper receiver, as certain steps and requirements may differ based on the components and AR-15 upper you’re using. You will want to perform this same final inspection when building an AR-15 piston upper as well.

Do Different AR-15 Uppers Have Different Build Instructions?

Yes, different types of AR-15 uppers have different build instructions. It can even differ between models. Therefore, always refer to your AR-15’s manufacturer instructions for specific builds.

Trust me, being meticulous with advanced builds is crucial. I’ve ruined a lot of AR-15 upper parts by being impatient or not reading the instructions thoroughly.

How Does Upper Build Quality Affect Performance?

Upper build quality directly affects performance. When you install high-quality parts such as a ballistic advantage barrel or even a rugged dust cover, it can improve the accuracy, durability, and overall performance of your AR-15.

These high-quality AR-15 upper receiver parts might cost more initially, but in the long run, you’ll likely save a ton of money by reducing the need for replacements or adjustments. Plus, paired with other AR-15 modifications, it makes for a more enjoyable shooting experience.

What Other Modifications Can Be Made To Your AR-15?

Other AR-15 modifications you can make include triggers, grips, stocks, and changing the caliber and coating. However, the first modification I always make, and the one I believe is the most important, is to install a scope on your AR-15 – it’s the modification that offers the most significant increase in precision and shooting performance.

Can You Install A Scope On Your AR-15 Upper?

Yes, you can install a scope on your AR-15 upper. We at HuntersHalt always recommend novice buyers install a scope on your AR-15. However, you’ll need the right mounting equipment and rail space. Then, you just need to decide what AR-15 scope you’re mounting – red-dot sights, LPVOs, or hunting scopes.

Can You Also Build Your AR-15 Lower Receiver?

Yes, you can build your AR-15 lower receiver. In fact, if you are considering building your AR-15 upper, then it is recommended to build your AR-15 lower receiver to truly get that full custom rifle experience.

How To Disassemble An AR-15 Upper?

To disassemble an AR-15 upper, you should pull the charging handle to the rear to open the upper receiver, exposing the bolt carrier assembly. Then you’ll be able to slide out the bolt carrier group (BCG) and then remove the charging handle by sliding it downward. By field stripping your AR-15 correctly you’ll be able to inspect for damage & keep them clean.

Frequently Asked Questions

The Bottom Line

Building your own AR-15 upper receiver is an incredibly rewarding experience. It offers a deep connection and understanding of your firearm. Therefore, when you have the right tools and a little bit of patience, you can create a custom upper that matches your exact specifications and needs. Just remember to do everything by the book – a well-built AR-15 is a tool you can rely on!