AR-15 Beginners Guide: How to Build a Lightweight AR-15

Hobbies are enriching to anyone’s life and building an AR-15 is a rewarding endeavor for the rifle enthusiast. Discover how to build a lightweight AR-15 here.

The AR 15 is one of the most famous firearms in the USA. This weapon has a complex and fascinating story that goes back to the mid-1950s when it was first created by ArmaLite. However, it wasn’t until it was sold to Colt that the AR 15 craze began. 

With the AR 15, it’s the lower receiver that handles the firing capabilities. The lower receiver is also the part that has the serial number. Because of this, you’re extremely limited to what you can do with the lower receiver when trying to make a lightweight AR 15. 

On the flip side, the upper receiver is essentially fair game for DIY builders. So continue reading and we’ll walk you through how to build your very own lightweight AR 15. 

Install the Forward Assist Assembly 

Collect all of the parts you intend to use to build your AR 15. The specific brands and pieces you choose is entirely up to you. That’s what makes this process so unique and fun.

Now, clear your space so that you have a dedicated work area. Once the workspace is prepped, you’re ready to start building your AR 15. 

The very first step is to take your upper receiver and lie it upside down. When you do this, you should notice that the Picatinny rail is lying against your work surface. Now, slide the forward assist in the forward assist spring.

Then, you want to push the pin through while you hold down the forward assist assembly. Once you do this, the forward assist will now be able to move easily up and down when you’re compressing it. 

Install the Ejection Port Cover Assembly

Before you start this step, it’s important that you check and make sure that your safety glasses are securely on.

Take your ejection port cover pin snap ring and push it gently into the ridged area that’s on the back end of the ejection port cover pin. Now turn the upper receiver so that it’s lying on its side. This is so that the barrel threads will be pointing to your right and the ejection port will be facing up toward the ceiling.

Line up the upper receiver’s holes with the holes on the ejection port cover. Now, place the upper receiver under the ejection port. Push the cover pin into the hole of the upper receiver.

You should push only until the pin starts to poke out of the second hole. Now, hold the cover spring in your left hand. With your right hand, take the long part of the spring and rotate it clockwise – one full revolution.

After you wind the spring, slide in the ejection port cover pin as far as you can. The ejection port cover pin should eventually be blocked by the ejection port cover pin snap ring. Once you hit the ejection port cover pin snap ring, close the ejection port cover.

Congratulations! You just built your AR 15’s injection port assembly.

Build the Bolt Carrier Assembly

The first step in this process is to drive the bolt through the bolt carrier. Drive the bolt in as far as you possibly can. Then, slide the hole of the bolt carrier over the bolt cam pin. 

Once the pin is securely in, twist the pin so that the front and back of the bolt carrier are lined up with the holes in the bolt cam pin. Now, push the firing pin into the bolt carrier. Just like the bolt, you want to slide the firing pin in as much as you can. 

After, push the firing pin retaining pin into the bolt carrier. There is the part of the bolt carrier that’s hollow. You want the firing pin retaining pin to go into that hollow area. 

Congratulations again! Your AR 15’s bolt carrier assembly is now complete. 

Assemble the Charging Handle Assembly

For this part of the process, you need to put the charging handle latch spring into the charging handle. Now, as you push the charging handle latch spring into the handle, you also want to line up the holes. The holes of the charging handle need to match up with the charging handle latch roll pin.

Install the Bolt Carrier Assembly and Charging Handle Assembly 

Just like in our first step, your upper receiver should again be upside down. Also, the Picatinny rail should by lying against your work area. Get your newly built charging handle assembly into the upper receiver. 

To do this, you have to line up the tabs of the charging handle with the ridges of the upper receiver. Then push the charging handle assembly into the upper receiver as deep as possible. 

Once the charging handle assembly is inside of the upper receiver, pull the bolt out of the bolt carrier. Pull it as far out as the bolt carrier will let you. The goal is to make sure that the bolt cam pin isn’t touching the interior of the upper receiver.

If the bolt is too far in, then the bolt carrier won’t fit properly into your AR 15’s upper receiver. Now, turn the bolt face so that the barrel threads and the bolt carrier assembly are facing each other. Push the bolt carrier assembly deep into the charging handle assembly.

Once you do that, insert the bolt carrier assembly, as well as the charging handle assembly, into your upper receiver. 

Put the Upper Receiver into the Action Block

Now your upper receiver is just about ready to go into the action block. First, you have to remove the Charging Handle and the bolt carrier assembly from the upper receiver. Once you do that, push the action block Insert into the upper receiver.

When you do this, the ejection port is going to open up. One of the reasons for having an action block Insert is so that the upper receiver will remain free from damage when you go to tighten it. 

Now, close the cover of the ejection port and then push the upper receiver into your action block. Once the upper receiver is completely in, close the action block and tighten it. Make sure that you don’t overtighten it though. 

Install the Barrel and Outer Receiver Nut onto Barrel Threads

Take your barrel component and push it into the upper receiver. The barrel’s pin must line up with the hole in the upper receiver. Push the barrel in as far as the upper receiver will let you. 

Remove the outer receiver nut and the inner barrel retainer nut from your tube handguard. Now, separate the inner barrel retainer nut from the outer receiver nut.

Follow this by wiping the barrel threads down with white lithium grease or anti-seize. This is so that the threads won’t corrode. Then, connect the barrel threads with the outer receiver nut. 

Screw the outer receiver nut all the way except stop before it can make contact with the ejection port cover pin. Now, twist outer receiver nut counterclockwise by one revolution. When you do this, the outer receiver nut’s gas hole should be lined up with the gas hole of the upper receiver. 

Now, take your white lithium grease or anti-seize and sipe down the threads of the inner barrel retainer nut. Then, connect your takedown wrench to the inner barrel retainer nut. Tighten the retainer nut as much as you can without stripping it. 

Install the AR-15 Gas Block and Gas Tube 

You will have to put the gas tube into the upper receiver’s gas holes as well as the gas holes of the inner barrel retainer and outer receiver nut. Now, push your gas block into the barrel. The gas tube then goes into the gas block.

Once you do that, screw plug screws onto the top part of the tube handguard. Then, push sling studs into the tube handguard. Now, screw the sling studs into the retainer nut.

Line up the screw holes of the outer receiver nut with the holes of the tube handguard and then screw in flat-headed screws. 

And that’s all there is to it! All you have to do is connect this completed upper receiver with a legally permitted lower receiver and then you can start using your rifle.

If this all seems too complicated or time-consuming, you can always just purchase a high-quality AR 15 complete upper receiver assembly. 

The Importance of Knowing How to Build Your Own Lightweight AR 15 

Any gun enthusiast can go ahead and purchase a pre-built weapon. But a person who is actually passionate about the craft and the art of shooting will find great pleasure in building their own lightweight AR 15. 

Are you interested in reading other helpful articles like this one? Then check out the rest of our blog for more!