AR-15 Upper Assembly Guide (2023 UPDATED) Must-Read

AR-15 Upper Assembly Guide
Alfred Mendoza

Understanding and learning how an AR-15’s upper receiver is put together not only allows you to assemble a perfectly functioning upper receiver out of parts but also allows you to do regular maintenance. =

To guide you easily about assembling your AR-15 upper receiver, our team listed below the procedures that you can use.

11 Steps To Follow In Assembling An AR-15 Upper

1. Gather The General Tools & Supplies 

The receiver, barrel, handguard, bolt control group or BCG, gas block, charging handle, and gas tube are all required parts for any style of AR-15. [1]

To make sure the installation runs smoothly, you’ll need a few general tools. An upper receiver block, vice, hammer or rubber mallet, 1/2 inch torque wrench, wheeler torque wrench, AR-15 combo tool, feeler gauge, and a headspace gauge are among the tools needed. 

2. Install The Upper Receiver

This process is for a stripped receiver. If you have an assembled upper receiver component, you can skip this step. To begin, place your upper receiver in your vice’s block and either install the forward assist or double-check that the FA’s teeth are facing the receiver itself if it is installed already.

Place the vice block in the vice; a towel should be placed beneath the receiver unit to prevent the vice from scratching the surface. Make sure the FA is in place, then use one of your punches to tap the roll pin.

3. Install The Bolt Carrier Group

To begin installing the BCG, place the bolt into the carrier with the extractor to the right side. The lightweight titanium and aluminum, together with the tuned adjustable gas block (with gas tube roll pin), will provide a light recoil for a competition build. Install the cam pin by aligning it with the cam-pin hole in the bolt. 

The cam pin must be placed lengthwise through the bolt carrier. Rotate the pin 90° while it is seated. The pin should be able to freely travel within the slot. Then, at the back of the bolt, insert the firing pin and press it in as far as possible, and last, in the hole on the left side of the carrier, insert the firing pin.

4. Install The Barrel

First, lubricate the barrel extension and threads of the barrel nut with grease or gun oil. Put the barrel into the receiver with the index pin in place. Because most handguards have the tool for removing the nut, the AR Combo Tool isn’t required. However, the torque wrench will still be necessary. It is designed to fit into the square hole on the given tool.

Tighten the nut until one of the spaces between its teeth perfectly clears the receiver’s gas tube hole. Barrel nut torque is usually between 40 and 80 ft-lbs. You must need barrel nut spacers if your upper receiver build is less than 30 in-lb or more than 80 in-lb. But it is recommended to use lightweight barrels for a lighter rifle as well.

Install The Barrel

5. Install The Gas Block 

It’s time to install the barrel gas system now that the nut is in place. To do so, slip the gas block over the muzzle and align the gas tube with the receiver’s gas port. Ensure the tube is parallel to the barrel and the block isn’t twisted to one side. Hand tightens the two set screws on the underside of the gas block.

6. Install The Charging Handle

With an AR charging handle, you’ll be able to get things started right away. When you retreat on the charging handle, the bolt is also pulled back. The charging handle is normally complete and ready to use, making installation simple.

Grab the charging handle by the T and place it in the upper receiver’s slot. Insert the bolt carrier group with the bolt forward and slip the charging handle for about halfway. The BCG’s gas key should fit into the charging handle’s groove, and then both the charging handle and the bolt carrier group should be pushed into the chamber.

7. Install The Free-Float Handguard

The purpose of a standard AR handguard is to make it simpler to grasp the rifle with your support hand while simultaneously protecting it from the hot barrel.

A free-floating handguard, on the other hand, has a lot more advantages. 

To put it together, slide the barrel nut over the barrel and hand tighten into the receiver, then slide the float tube, gas tube, and front sight base onto the barrel. Replace the pins in the base and screw the float tube onto the barrel nut.

Install The Free-Float Handguard

8. Install The Gas Tube 

The gas tube is also part of your AR-15’s gas system. Locate your gas block and gas tubing; insert the gas block first, then the tube through the larger hole. When installing the gas block, make sure the gas hole is facing down so that each hole is aligned properly. Take the roll pin and squeeze one end with pliers.

The gas tube should go on fairly easily, but use a hammer to tap it in place if it doesn’t. To keep everything in place, use the vice. The gas tube should be able to glide over the barrel with ease. Make sure it’s perfectly aligned. Your barrel should include a few words that go well together.

9. Install The Muzzle Device

Installation instructions will be included with your muzzle device. However, if you want to make it easy, you can use a reaction rod. Place your muzzle device in place. Place the smaller side of the crush washers toward the barrel if it comes with them. Use a crush washer. Make that big ports on the side and top holes aligned. 

Follow the manufacturer’s instructions for timing your device so that the holes that divert gas flow at the muzzle help to drive the rifle in a recoil-reducing direction. Lubricate the barrel threads and the threads inside your muzzle device with a little amount of lubrication.

10. Install The Forward Assist

There are three components to the forward assist assembly. A roll pin, a return spring, and a forward assist. In installing forward assist, secure the receiver in a vice and grease the forward assist and return springs. After that, slide the spring onto the forward assist and into the receiver’s hole. 

Level the forward assist with the receiver’s hole and secure it with a slave pin. Punch the roll pin through both the receiver and the forward assist until it is completely flush. When you release pressure on the forward assist button, it should bounce back.

Install The Forward Assist

11. Install The Ejection Port Cover

You can now proceed to ejection port cover assembly. An ejection port cover is often called a dust cover. The cover, a rod, an e-clip, and a spring make up the dust cover. To begin, Install the C-shaped snap ring with pliers, or if you’re lucky, the snap ring may already be on the pin. 

If it doesn’t, you’ll have to insert it using pliers. Place the ejection port inside the middle exposed section and slide the hinge pin inside. Twist the spring 180° with the long end toward you and the table. Push the rod through it and place it in the center. When properly installed, it should have adequate tension and desire to remain open.

5 Shot Placements/Angles

5 Shot Placements/Angles

Bench Vise

Holding your workpiece in place is half the battle, as any machinist will tell you. Because you’ll be punching and tightening a lot, having a secure way to hold your AR upper receiver in place is essential. 

Upper Receiver Block

An upper block is one of your most vital tools in assembling your AR-15 upper receiver because it ensures that the barrel does not get crushed, bent, or scratched during installation. If you don’t have one, borrow or purchase one.

Brass Punches

Punches are excellent for fitting pins into and out of tight spaces without ruining your finish. Brass is the greatest option since it does not tarnish and is also suitable for other gun applications. If that’s all you have, any punch will suffice. 


A grease is used to attach the barrel nut and a few items you don’t want to get stuck on within your AR-15 upper receiver. A white lithium grease, general-purpose gun grease, or machine oil can suffice for your AR-15 upper receiver.

Feeler Gauge 

This tool makes it simple to place the gas block exactly 0.025 inches from the barrel shoulder. If you don’t have one, equal-length business cards will suffice.

1/2″ Torque Wrench 

When installing the barrel nut, this tool ensures that the proper torque is applied.

Punch Set

A brass punch set is the greatest option since it does not tarnish and is suitable for other gun applications. If that’s all you have, any punch will do. 

AR-15 Combo Tool 

This tool is also useful for castle nuts on the lower receiver.

Jeweler’s/Gunsmith Mallet/Hammer

A simple mallet enables you to strike on punches without fear of injuring yourself with a missed strike, but the best are those with rubber or plastic ends to prevent the finish from being marred. 

Wheeler Torque Wrench 

This tool is great for mounting scopes, but it’s also handy for keeping the image of the equipment necessary for AR-15 torque and the gas block identical.

Headspace Gauge 

This tool will inform you if your rifle’s headspace is accurate. This tool may not be necessary if you get your barrel from a respectable dealer, but it’s a small price for some individuals to pay for the peace of mind that comes with knowing everything is in order.


No, it is not difficult to assemble an AR-15 upper if you have the proper tools and supplies and the knowledge about AR platform and assembling.

To assemble an AR-15 upper, it will take you about 30 minutes to 1 hour. If you’re knowledgeable enough and have the right tools, it will just take you 20 to 30 minutes.

It is not dangerous to build your own AR-15 upper. Just make sure to follow the step-by-step process of assembling your AR-15 upper to avoid mistakes and prevent danger. Always unload your firearm before beginning the process and wear safety glasses and gloves.

Final Thoughts On Assembling An AR-15 Upper

You can construct your AR-15 upper receiver in one of two methods. The other procedure was somehow similar to this guide, but it only differs in the tools that have been used. The second build for the AR-15 upper receiver uses some sets of screw-based blocks, adjustable gas blocks, and a barrel nut with gas tube alignment tabs. 

Now that you’ve seen one of the procedures to build your AR-15 upper receiver, we hope that this guide helped you as you customize and build your own AR-15 upper receiver. Remember to shoot responsibly. Happy assembling!



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