Build Your Own AR-15 Rifle from an Aero Precision AR-15 Builder Kit

Tom Mchale gives the reader a detailed look at how to build your own AR-15 rifle, featuring an Aero Precision AR builder kit and a downloadable list of tools and parts. Also, AmmoLand is giving this gun away, register here.

Here's your new rifle! Don't worry, we're going to put it together. Read on for details.
Here's your new rifle! Don't worry; we're going to put it together. Read on for details.

USA –-(Ammoland.com)- Hey, here’s an idea. Let’s build a super spiffy AR-15 rifle! Better yet, let’s build an AR rifle and then give it away to one of AmmoLand daily digest email readers!

Thanks to Ammoland, Aero Precision, and Brownells, the super cool Aero Precision Arctic Camo AR-15 Rifle we’re going to build before your very eyes can be yours. Stay tuned for more info on how to win it.

So what’s this rifle all about? We started with the Aero Precision M4E1 Enhanced Arctic Camo Builder Set. [Note this arctic camo pattern is only available for a short few months, but the build instruction below would work with any of the Builder Sets Aero offers through out the year.]

These kits are hand finished by Blown Deadline, and they look, well, epic. The standard kit only includes the lower receiver, upper receiver, and handguard, but the Aero folks have an option to buy a Magpul CTR Stock, Magpul MOE Grip, and Magpul PMAG 30-round Magazine – all finished in matching Arctic Camo.

We’re going to cover all the parts used in this rifle kit build in our complementary feature, “Aero Precision Dream AR-15 Rifle Project – Picking Parts & Components“. In this article, we’ll focus on how you can build the same AR-15 rifle and show you how we put it all together, including the gun smithing tools we used to make the complete AR15 rifle kit build go smooth.

Tools You’ll Need For Any Rifle Build

While you can build your own AR-15 rifle kit on the cheap with fewer tools, having the right ones makes the job a lot easier / fun. More importantly when you have a sweet custom finished rifle like this one, using the right tools reduces the odds of unsightly scrapes, scratches, and dings. You can buy all of these at Brownells and have them in your workshop in a couple of days.

For an "assembly" like this, you'll want a couple of custom rifle builder tools like these that will help you out when you build your own Ar-15 rifle.
For an “assembly” like this, you'll want a couple of custom rifle builder tools like these that will help you out when you build your own Ar-15 rifle.

Get a Brownells AR Armorer’s Wrench. You’ll use this forever, and it has many purposes including installing the receiver extension, barrel nut, muzzle devices, and attaching torque wrenches.

  • A Nylon and Brass Hammer has lots of uses for driving pins and settling parts into place. The brass side provides some oomph when needed while the nylon end won’t damage the finish.
  • A Gunsmith's Alignment Pins Tool Set  Get the set as you will use all of them. The alignment tool is used for keeping trigger parts in place while you drive in mounting pins.
  • One way to prevent marring up nice parts is to use the right tools.The Brownells Extra-Large Bench Block allows you to drive pins in and out of parts without scratching.
  • A lower AR-15/M16 Action Block & Lower Vise Block Set allows you to mount the rifle by the magazine well so you can work on the lower or whole rifle securely. It’s like an extra pair of hands and is a great help for cleaning too. This kit has an upper receiver mount also, so you can hold that in place while installing gas systems, handguards and muzzle devices.
  • A Roll Pin Punch Set, these are made explicitly for those hollow pins that attach the gas tube to the gas block and the bolt release to the lower receiver. These punch tools won’t crush those hollow-center roll pins.
  • A General Purpose Torque Wrench connects to your armorer’s wrench and allows you to tighten the barrel nut and receiver extension tube nut with the proper amount of torque.

You’ll want to stake the receiver extension nut in place so it can’t come loose. A 5/32″ Center Punch like this will do the job.

There are other nifty tools available, but you can get the job done with this basic set of gunsmith tools. Lets get to the gun building.

Build Your Own Ar-15 Upper Receiver

Install the AR barrel and barrel nut

Use some anti-seize on the receiver threads before installing the barrel nut.
Use some anti-seize paste on the receiver threads before installing the barrel nut.

For this AR15 rifle build we used an Aero Precision 18″ .223 Wylde Fluted Stainless Steel Barrel . Aero Precision includes a custom barrel nut wrench. Well, it’s more of a flat that sticks on the end of a torque wrench – you can’t use it on its own. (check the image below) But it does perfectly fit the fancy barrel nut to which the handguard mounts. Factory specs call for tightening the barrel nut to a torque of between 35 and 60 foot-pounds so, after coating the receiver threads with some Loctite Silver Grade Anti-Seize Stick Compound, I used my torque wrench to tighten this to 50 foot-pounds.

Remember to make sure the nut is properly aligned with the gas tube hole so the tube can enter the upper receiver unimpaired.

Use a torque wrench to tighten the barrel but. In this case we used 50-foot-pounds.
Use a torque wrench to tighten the barrel but. In this case, we used 50-foot-pounds. Note: I have the upper in the Action Vise Block and see the custom barrel nut adapter on the torque wrench

Install the AR15 Rifle Gas Block

A small roll pin fixes the gas tube to the gas block.
A small roll pin fixes the gas tube to the gas block.

This barrel is cut for a .750-inch gas block, and it slipped into place perfectly. First, I pinned the Brownells Black Nitride Gas Tube into the Midwest Industries Low Profile Gas Block, then positioned it on the barrel taking care to make sure that it was entirely vertical. This block clamps down with three hex screws and the block includes red Loctite to make sure everything locks in place securely. At this point, we’ve got the barrel, barrel nut, gas block, and gas tube installed, so it’s time to mount the handguard.

Before clamping the gas block to the barrel you'll need to thread the tube into the receiver.
Before clamping the gas block to the barrel, you'll need to hand insert the tube into the receiver.

Install the Rifle Handguard

Slide the handguard into place over the barrel nut.
Slide the handguard into place over the barrel nut.

The Aero Precision Gen 2 Enhanced Handguard has a nifty mounting system. A counter-threaded bolt draws two braces towards the center of the handguard where it mounts to the barrel nut. Read the instructions carefully, and you’ll correctly center this bracket on the first try. An included hex wrench is all you need.

The Aero Precision Gen 2 Enhanced Handguard locks into place with a counter-rotating screw.
The Aero Precision Gen 2 Enhanced Handguard locks into place with a counter-rotating screw.

Install the Rifle Flash Hider

I’ve always been partial to the tried and true Smith Enterprise Ar-15 Vortex G6-A3 Flash Eliminator and that’s what we chose for this AR rifle build. Since this flash hider has no required orientation, you don’t necessarily need a 1/2″ Crush Washer to give you perfect alignment as you do with a standard A2-type hider, but I used one anyway. The reverse pressure helps keep the flash hider mounted securely on the threads. I did use a couple of drops of Red Loctite Thread Locker as well. If you win and this rifle ends up at your place, then you want to change the muzzle device, gently heat it to release the Loctite before trying to remove.

One of the many uses for the Brownells Armorer's Wrench is installing this Smith Enterprise Flash Eliminator.
One of the many uses for the Brownells Armorer's Wrench is installing this Smith Enterprise Flash Eliminator.

Voila! Now we’ve got a completed AR15's upper receiver, and it looks great. It’s time to build out the AR lower.

the top half looks pretty nifty, doesn't it?
The top half looks pretty nifty, doesn't it?

Building the AR Rifle Lower Receiver

You'll need a Lower Receiver AR15 Parts Kit with latches, pins, and springs. We got one without a trigger group because Brownells provided a Geissele AR trigger set.

You'll need a lower parts kit with latches, pins, and springs. We got one without a trigger group because Brownells provided a Geissele trigger set.
You'll need a Lower Parts Kit with latches, pins, and springs. We got one without a trigger group because Brownells provided a Geissele trigger set.

Magazine Catch Installation

Install the magazine catch lever and spring from the left.
Install the magazine catch lever and spring from the left.

We get to start with an easy one. Technically, no tools are required although the Brownells vise block for the lower receiver makes most of the remaining steps much more manageable. It’s like an extra pair of hands to hold your lower receiver securely while you do important fiddly stuff with the parts.

The magazine catch screws into the magazine release button.
The magazine catch screws into the magazine release button.

Insert the magazine catch into the left side of the receiver. From the right, place the magazine catch spring followed by the magazine release button. If you push the button in from the right, the magazine catch itself will extend out the left side of the receiver. Rotate the catch, so it tightens down on the magazine button threads. When the two pieces are flush, test it out. That’s it.

If you push the magazine release button into the receiver you can rotate the catch lever to tighten the two parts.
If you push the magazine release button into the receiver, you can rotate the catch lever to tighten the two parts.

Bolt Catch Installation

Insert the bolt catch spring and plunger into the receiver before installing the catch itself.
Insert the bolt catch spring and plunger into the receiver before installing the catch itself.

The lower parts kit includes a spring and plunger that go into the receiver. Install these, compress them, and hold the bolt catch and release lever in place. Most kits use a roll pin to hold this part and pressing or driving the pin is is where many folks scratch their rifle build, but the Aero lower receiver uses a small pin that operates as a hex screw, eliminating the danger of scratching or worse, breaking your lower..

A roll pin, or in this case a screw, holds the bolt catch/release lever in place.
A roll pin, or in this case a hex screw, holds the bolt catch/release lever in place.

Pivot Pin Installation

The pivot pin spring and detent are a bit of a pain to install. A tool makes it easier but you can do it the manual way using a small punch to hold the spring in place.
The pivot pin spring and detent are a bit of a pain to install. A tool makes it more manageable but you can do it the manual way using a small punch to hold the spring in place.

This one takes a bit of patience because the parts are small and under spring pressure. If you’re going to do more than one rifle, you might want to invest in a Brownells AR-15 Pivot Pin Detent Installation Tool. I did it the hard way without too much grief. Install the detent spring into the receiver followed by the small detent pin. Using a punch, compress that into the receiver while installing the pivot pin. Be careful not to let the spring and detent pin fly because they’re small and get lost easily. The pivot pin has a flat side and interior channel that captures the detent pin so once installed; the pivot pin won’t come entirely out of the receiver.

You need to insert the pivot pin without letting the detent spring and pin fly.
You need to insert the pivot pin without letting the detent spring and pin fly.

Trigger Group Assembly

This Geissele trigger set came with a slave pin that held the parts together while I drove in the trigger pin.
This Geissele trigger set came with a slave pin that held the parts together while I drove in the trigger pin.

Depending on the trigger system you choose, instructions may vary. The Geissele SSA Trigger we chose for this rifle installs like a standard AR-15 trigger group. The trigger goes in first, and you can use the alignment punch to hold the trigger and its spring in alignment with the holes in the receiver. Install the trigger pin while driving out the alignment punch. In this case, the Geissele kit included a slave pin that held the parts together while I installed the permanent trigger pin. Once that’s in place, you can remove the hammer pin, install a bit of lubricant in the hole, then place the hammer and spring in the receiver, taking care to rest the hammer spring legs on top of the trigger pin. The closed loop of the hammer spring should be behind the hammer body itself.

The hammer and spring also install with a simple push pin.
The hammer and spring also install with a simple push pin.

Safety Selector and Pistol Grip Installation

You have to install the safety lever before the pistol grip.
You have to install the safety lever before the pistol grip.

These parts go into place together because the detent pin and spring that moderate the safety lever operation are held in place by the pistol grip. Turn the receiver upside down in the vise block tool and install the safety lever through the receiver and rotate it to the “safe” position.

Drop the safety lever detent pin into the receiver like this.
Drop the safety lever detent pin into the receiver like this.

Now, drop the safety detent pin into the receiver hole.

With the safety detent spring placed into the pistol grip, install it carefully so you don't bend the spring.
With the safety detent spring placed into the pistol grip, install it carefully, so you don't bend the spring.

Place the safety detent spring into the pistol grip and position the pistol grip on the receiver taking care not to bend or kink the detent spring. Compress the pistol grip into position and insert and tighten the grip screw into the receiver.

Tighten the pistol grip to the lower receiver.
Tighten the pistol grip to the lower receiver.

Build Your Own AR-15 Rifle : Test Safety & Trigger Operation

Now you can test the trigger and safety operation. Put your thumb in front of the hammer, so it doesn’t slam against the receiver. With the safety lever on “safe” and the hammer cocked, press the trigger – hard. The hammer should not fall. Now, flip off the safety and press the trigger, catching the hammer with your thumb. It should fall. Finally, after recocking the hammer, press the trigger again, but hold it back. While continuing to hold the trigger to the rear, cock the hammer manually and then allow the trigger to move forward. You should hear and feel the trigger reset.

At this point you can test the trigger group and safety.
At this point, you can test the trigger group and safety.

Install the Receiver Extension Tube

Put the receiver extension tube nut and receiver endplate on the tube like this.
Put the receiver extension tube nut and receiver endplate on the tube like this.

We chose the Brownells Mil-Spec Buffer Tube Assembly, so everything we needed was included. Thread the receiver extension nut onto the receiver extension tube with the open slots facing the rear of the tube. Next, place the receiver end plate over the threaded end of the receiver extension with the dimple facing forward. That will lock into the back of the receiver itself. Thread the tube into the lower receiver until the front of the tube almost starts to cover the buffer assembly spring and detent pin hole in the receiver.

Screw in the buffer tube until it's just short of the retainer pin hole.
Screw in the buffer tube until it's just short of the retainer pin hole.

Now drop in the buffer retainer detent spring, covered by the retainer. Compress the retainer and spring and screw the tube in until it holds the retainer in place.

After you drop the retailer spring and pin into place you can screw the buffer tune into the receiver until it holds the pin in place.
After you drop the retainer spring and pin into place, you can screw the buffer tube into the receiver until it holds the pin in place.

Now you can install the rear takedown pin. The detent spring and pin that hold it in place are secured by the receiver end cap. Insert the takedown pin detent pin into the small hole in the rear of the receiver followed by its spring. Be sure that the groove in the takedown pin faces to the rear so the detent pin will fit into it.

Insert the rear takedown pin and the retention pin through the rear of the receiver.
Insert the rear takedown pin and the retention pin through the rear of the receiver.

The receiver end plate will hold the spring and pin in place. Carefully press the receiver end plate into position while tightening the receiver extension tube nut by hand. When all is secure, you can tighten the receiver extension nut using the armorer’s tool and torque wrench. The proper torque is usually 40 inch-pounds but check your instructions.

The receiver end plate holds the rear takedown pin detent pin and spring in place.
The receiver end plate holds the rear takedown pin detent pin and spring in place.

Last but not least, you’ll want to stake the receiver extension tube nut in place. Using the center punch and a small hammer, dimple and move some metal from the end plate into the front-facing notches on the receiver extension tube nut. That will prevent the nut from turning.

Here, I've used a center punch to stake the receiver end plate to the receiver extension tube nut.
Here, I've used a center punch to stake the receiver end plate to the receiver extension tube nut.

Now that the tube is installed, you can insert the buffer spring and buffer. The retention pin will hold the buffer and spring in place.

Once you insert the buffer spring and buffer and add the buttstock, you've got a completed lower.
Once you insert the buffer spring and buffer and add the buttstock, you've got a completed lower.

Now we have a completed lower receiver, and you’re ready to mate the upper and lower receivers.

Since we used the Brownells completed bolt and carrier group, that just slides into the upper along with the charging handle.
Since we used the Brownells Nickel Boron completed bolt and carrier group, that just slides into the upper along with the charging handle.

Once you have inserted the Brownells Nickel Boron Bolt and Carrier Group and BCM Gunfighter Ambi Charging Handle you can attach the upper and lower receiver with the forward hinge pin first. With the upper receiver open, place the charging handle in the upper receiver and slide the bolt into place. Push the bolt forward into the upper receiver and secure the receivers with the rear takedown pin. Now that you have built your own AR-15 should now have a working rifle that’s ready for optics installation.

The rifle is now ready for optics, anyone can build your own AR-15 rifle.
The rifle is now ready for optics, anyone can build your own AR-15 rifle.

We installed a Vortex Strike Eagle 1-6×24 Optic using the Warne X-Skel Scope Mount. To do this right, you’ll want a small torque wrench like the Nightforce Scope Ring Torque Wrench so you can tighten the scope rings properly. This Warne system calls for 25-inch-pounds of torque. This rifle is ready for range testing, so stay tuned, and we’ll cover that in the next story.

The finished product!
The finished product!
Tom McHale
Tom McHale

About

Tom McHale is the author of the Practical Guides book series that guides new and experienced shooters alike in a fun, approachable, and practical way. His books are available in print and eBook format on Amazon. You can also find him on Facebook, Twitter, Instagram, and Pinterest.

  • 11 thoughts on “Build Your Own AR-15 Rifle from an Aero Precision AR-15 Builder Kit

    1. Where can I buy an AR15 kit? I’m in Calif.
      My dad used to drill out barrels during WWII, and built rifles at home on the side.

    2. Keep a small flat refrigerator magnet and tweezers on work bench/table to manage springs and small pins. Trays are nice, but springs always manage to pop out of bins at worst possible time.

    3. One more little tip the pivot pin from a good kit has a hole near the tip . A straightened paper clip ( I like the larger ones ) pushed through it will depress the spring and detent while you insert it in the hole of the lower .

      1. @Ronald Moore… Have a ball it gets addicting . Next try the 80% lowers. Only problem with an AR project is 1499 springs plus the one you can’t find . Good habit to purchase extra spring kits to have on hand .

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