Starting your own AR-15 build can feel like a daunting challenge, but it doesn’t have to be. In fact, for many gun lovers, it’s an oft-repeated hobby that just brings even more enjoyment to arguably the most popular gun in America. 

I mean, they call the AR-15 “America’s rifle” for a good reason. There are a ton of choices for AR uppers, lowers, and triggers out there. Plus, it can be an easy way to learn more about how your AR works and save money while making the exact gun you want.

So, here’s how you can build, shoot, and enjoy your own homemade AR-15 in 10 easy steps.

Table of Contents

1. Intro to Building an AR-15
2. Tools You’ll Need
3. Picking the Right Lower
4: Installing the Trigger Guard, Bolt Catch, & Mag Release
5. Installing a Mil-Spec Trigger
6. Installing a Drop-In Trigger, Detent Spring, Safety, & Grip
7. Installing Buffer Spring, Stock, Takedown Pins, & Front Detent
8. Completing the AR With an Upper Receiver
9. Rounding Out Your Build With Accessories
10. Shooting Your Home-Built AR Rifle/Pistol

1. Intro to Building an AR-15

 


The AR platform lends itself to do-it-yourself gun projects. The tools needed are simple, parts are readily available, and almost anyone can complete the build with only moderate experience. There’s something distinctly American about building your own rifle, and it’s just plain fun to have a gun you put together with your own two hands.

This article will walk you through the process and some of the special benefits, like cost savings and customization, that draws hundreds of thousands of gun owners to make their own AR or even just modify one they already have. 

To start, you’ll need to gather a few things:

  • Lower receiver, the technical serialized “gun” portion of an AR
  • Lower parts kit, complete or partial depending on your needs
  • Trigger and fire control group, if you choose to get a partial parts kit
  • Upper receiver, barrel, and gas system
  • Handguard and any other extras you want 
  • And a few tools to get everything put together
     

2. Tools You’ll Need
 


Let’s get started by looking at the specific tools you’ll need for your build. Don’t worry, it’s pretty simple, and you won’t need an entire gunsmithing shop to make it happen. Heck, you probably already have a few of these on hand.

Here’s our short list of tools you should have ready:

  • Hammer and punches, brass or polymer are great options to protect the gun’s surface
  • Screwdriver set with various bit sizes and shapes
  • AR wrench/building tool
  • AR vice block, not required but very helpful and quite affordable

There are other options, but that’s all you really need for a basic AR build.
 

3. Picking the Right Lower for You
 


Not all lowers are equal, much less built to do the same thing. These can either come as completely stripped lowers with none of the parts that go inside, or they can come as partially complete or fully complete versions as well. Because this is the serialized portion of the gun – the part ATF considers to be a firearm – your lower is the one piece in your build that will normally require you to go through a background check with a Federal Firearms License dealer. 

But you need to pick the lower that’s right for your build before that happens. There are plenty of styles of lowers, from budget-friendly polymer ones from makers like Plum Crazy to standard mil-spec lowers – i.e. built to basic military specifications – and more customized options from makers like Anderson Manufacturing, Aero Precision, Spike’s Tactical, ATI, Yankee Hill Machine, and many, many more.

First, decide if you want a forged lower that is the most common, but normally falls into the affordable/less-refined category, or a billet/milled receiver that is more precisely machined instead of forged. Both will work, but you may see some looser tolerances on a budget-friendly forged option compared to a milled one.

Then, decide just how much “building” you want to do. If you want to do more, pick a stripped option. If you’re not looking to deal with as many small parts and pins, you can always go with a complete or semi-complete option instead. 

4. Installing the Trigger Guard, Bolt Catch, & Mag Release
 


Once you have your tools, lower, and the parts kit, you get to dig into the actual build itself. Let’s start with the trigger guard, bolt catch, and magazine release. Installing these parts will set us up for the next step, which will be dropping in the trigger. 

Starting with the trigger guard, it’s an easy and simple process to slide it into cuts in the receiver bottom and then mount the associated screws or pins to hold it in place. This is one of the places where you’ll want to use that polymer or brass hammer to protect the receiver’s finish.

With that done, we can move on to the slightly more complex bolt catch. Just insert the spring and the detent on top and slide the bolt catch/release over that. There will be some spring tension for the next step when you drive in the pin to retain the catch. Hold it aligned with the pin hole on the catch and receiver and drive in the pin with the hammer and punch. It can be a little finicky, but a little patience goes a long way.
 

AR Lower Parts Kit
It might seem like a lot, but the lower really only has a handful of parts, most of which you will never need to remove after building it. (Photo: Samantha Mursan/Guns.com)


Finally, we move on to installing the magazine release. There are basically just three parts: the release button, spring, and connector. Slide the connector pin through the receiver, top it off with the spring, and press in the button. Once it catches, you can thread the button and the connector. I like to use a punch to press the connector out for threading until it rests flush with the receiver under spring tension.
 

5. Installing a Mil-Spec Trigger
 


Moving on to the trigger, we’ll start by working with a standard mil-spec trigger built to basic military specifications, because they are probably the most common. There are easier “drop-in” versions, but it’s good to understand how a standard trigger installs. 

Grab your trigger disconnect. There is a trigger-disconnect spring inside the trigger housing, sometimes attached or loose. Set the trigger disconnect into the spring/trigger housing and align the holes. Ensure the spring legs are forward of the trigger itself, and you can now place it inside the receiver. Position it so the pin holes align and insert the trigger pin. Then you can test it to make sure the trigger has spring pressure. 
 

RMT Nomad Trigger
The mil-spec trigger, right, takes a bit more work to install and is usually quite basic, unlike the drop-in RMT Nomad Trigger on the left. (Photo: Paul Peterson/Guns.com)


We’ll finish the install by adding the hammer. Hold the hammer’s spring legs forward so they can slide down the inside of the receiver, align the pin hole with the holes in the receiver, and press the push pins through to retain the hammer. Use your punch set to finish as needed. 

Or, if desired, just grab a drop-in trigger and make the whole process just a little bit easier. I’ll show you that below.

6. Installing a Drop-In Trigger, Detent Spring, Safety, Pistol Grip
 


This is about as easy as the name “drop-in trigger” suggests. Drop the trigger box into the receiver and grab your safety-selector switch. The safety itself has cuts for safe and fire modes. As you put in the trigger, align the safety with the holes in the receiver, slide it in, and rotate it into the fire position (down). 

The retaining pins normally push through, but you may need to give them a bit more of a push with your polymer/brass hammer until they are flush. We’ll then install the detent, spring, and grip. This will also hold the safety in place.
 

RMT Nomad Trigger
Drop-in triggers come as a simple, do-it-yourself package. (Photo: Paul Peterson/Guns.com)


There is a hole on the bottom of the receiver by where the pistol grip will go. Drop in the detent and add the spring on top. The pistol grip has a hole for the spring. Align the spring, hole in the grip, and the grip itself with the receiver. Press the grip down and tighten it into place on the receiver. Then give your safety a quick test to make sure that it positively clicks to the safe and fire positions. Now test your trigger and hammer to make sure they also function properly.
 

7. Installing Buffer Spring, Stock, Takedown Pins, & Front Detent
 


Start by partially threading your castle nut onto your buffer tube with the cuts on the nut facing the rear of the tube. Add your plate on top of the castle nut. This is also the point where you should choose if you want a plate with sling points for a single-point sling system. Then partially thread the tube onto the receiver – do not go all the way just yet. 

Thread the castle nut backward about as far as it will go – no need to make it tight. We’ll now install our buffer-retaining detent, which will hold in the buffer and buffer spring when we’re finished. There is a small hole by the buffer-tube threads at the rear of the receiver. Start by sliding in your detent spring and topping it off with your retaining detent. From here, I like to hold down that detent with a screwdriver. Try your best not to launch the detent across the room, but don’t feel that bad if you do. It’s a common issue.

Start threading the buffer tube deeper into the lower at this point. Once the tube is holding the detent in place on its own, remove the screwdriver, and rotate the stock slighty to the side. You should see a hole in the rear of the receiver. That will hold the small rear takedown-pin detent and spring. 
 

AR Lower
It's fairly obvious where the large, round buffer tube will screw into the lower. But try not to get too far ahead and over-tighten everything before you complete some of the other smaller steps. (Photo: Samantha Mursan/Guns.com)


Slide the rear takedown pin into the larger hole on the side of the receiver. Now you can drop a smaller detent pin into the rear and add the associated spring. Move the plate back to hold the spring and detent in place. This is why your rear takedown pin doesn’t pop out of the gun every time you take it apart for cleaning. It will eventually hold the upper and lower receiver together.

Use your hand to tighten down the castle nut to hold the plate in place. Grab your AR tool and lock the teeth of the wrench into the castle nut’s cuts to finish tightening it. Lastly, add the front takedown pin to the receiver by sliding in the spring followed by the detent to the holes at the front of the receiver. The front takedown pin has a channel that rides and locks in the detent. Now, slide the buffer spring and buffer into the buffer tube with the spring at the rear and buffer up front. Lock them into the tube by pushing them past the rear detent.
 

8. Completing the AR With an Upper Receiver
 


One of the great things about building your own upper is you can pick what kind of barrel and gas tube/piston you want. However, this is a much more involved process and does require some more tools and accessories. Buying one is often cheaper than making it … and much less painful.

Most people simply pick their own completed upper, which often includes the bolt carrier group and charging handle. There are tons of options to fit almost any need, caliber, barrel length, compensator, and handguard you could want. Plus, since this is not a serialized part, you can often have them shipped right to your house or grab one from a store. So, we’ll start there.

Your complete upper will rest on top of your lower. The front and rear takedown pins you installed on your lower will now simply press through like buttons and hold the top and bottom of the AR together. But now that you built the lower, you can turn your AR into almost any kind of rifle you want by just swapping out uppers in a few seconds. 

9. Rounding Out Your Build With Accessories
 


With your upper and lower in hand, you might still feel like there are a few things missing. You can put just about anything you want on the AR platform. I’m a huge fan of lights, especially if your AR is meant for home defense. You can get as fancy as you want, but there are plenty of budget options, too. 

Iron sights, even if you only have them as backup sights, are also great. But optics are all the rage right now and increasingly affordable. Add a variable-power optic, red dot, or whatever your heart desires. 

Slings are also one of the main things people overlook for AR builds. But if you’ve spent any significant amount of time carrying your AR, you’ll probably learn to love a nice sling. Finally, you must feed your AR, and there are plenty of classic metal mags or affordable but durable polymer options as well.
 

10. Shooting Your Home-Built AR Rifle/Pistol
 


Shooting and enjoying your new AR is the best part of building. You now have a complete rifle that can serve many purposes, from home defense and personal security work to varmint hunting. The AR-15 has become America's Rifle for good reason. It's versatile and widely used for many of the same reasons we just talked about. So what are you waiting for? Start building – and enjoying – your own AR-15 today, knowing that you're taking part in a great patriotic process.

revolver barrel loading graphic

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