The AR15 is one of the easiest weapon platforms to build yourself.

You can assemble these rifles at home with just a few basic tools. Because each part of the AR 15 can be changed and due to the extensive aftermarket for AR 15 parts, you can customize an AR15 to be the perfect silencer host.

Before we teach you how to build an AR-15, let’s cover the tools you’ll want to have on hand to make the job as simple as possible.

Recommended Tools for Building an AR15:

• Brass Punch Set
• Roll Pin Starter Punch
• Hammer or Mallet
• Armorer’s Wrench
• Torque Wrench
• Allen Wrench Set
• Aeroshell Grease
• Vice
• Eye Protection

Optional:

• ¼” Clevis Pin (Highly recommended)
• Upper Receiver Action Block
• Lower Receiver Action Block
• Armorers Bench Block

Before diving into the AR15 parts you’ll need and the directions for assembling an AR-15, we must prep our workstation.

Cleaning your work surface and the floor around you is good practice. AR15 Lower Parts kits contain a number of small springs and detents, which can easily get lost if they fall on the floor (or get launched into the atmosphere when you’re trying to install the takedown pins.) Having a clean work area will make finding these parts much easier if they get away from you.

Nothing is worse than putting your custom rifle build on hold because you can’t find a detent. As always, safety is a priority; make sure to wear eye protection when dealing with these small parts.

AR15 Lower Receiver Parts

• Stripped Lower Receiver
• Front and Rear Takedown Pins
• Bolt Catch
• Magazine Release
• Fire Control Group
  • Trigger
  • Hammer
  • Disconnector
• Trigger Guard
• Selector Switch / Safety
• Pistol Grip
• End Plate
• Castle Nut
• Buffer Tube
  • Buffer Weight
  • Buffer Spring
• Stock

NOTE: AR 15 Lower Parts kits contain most of these parts and do not need to be purchased separately.

How to Build an AR 15 Lower Receiver

We’ll start with the stripped lower receiver and build it from front to back, starting with the front takedown pin and ending with the buffer tube assembly.

Front Takedown Pin:

This singular part has caused more curse words to be yelled, tools to be thrown, and grown men to crawl on their hands and knees looking for a part than any other small part in history. Luckily, we have a trick that makes this installation easy.

Slide the ¼” clevis pin into the pivot pin holes from the bolt release side of the frame. Line up one of the clevis pin holes with the detent hole on the receiver. Slide the detent spring and detent through the clevis pin and into the receiver hole. Using a small punch push the detent into the receiver and slowly rotate the clevis pin, capturing the detent assembly in the receiver hole.

Now take your front takedown pin (the longer of the two takedown pins) and slowly press against the clevis pin, ensuring the groove on the takedown pin is facing the detent. As you slide the takedown pin into place, the detent will sit into position, locking the takedown pin into place.

You’ve just accomplished the most challenging part of building an AR15, congrats!

Bolt Catch:

Set the receiver flat on the magazine release side of the frame. The bolt catch slot should be facing upward. Drop the small spring into the hole inside the bolt catch slot, then set the plunger into the spring. The thinner side sits into the spring.

Now you’ll set the bolt catch into place, ensuring the hole on the bolt catch aligns with the roll pin hole on the receiver.

Using a roll pin starter punch, align the roll pin with the roll pin hole and begin tapping it into place with your hammer or mallet. Once the roll pin is started, you can use a brass punch to tap it until the pin is flush with the receiver body, allowing the bolt catch to be actuated.

Magazine Release:

With the receiver in the same orientation as the previous step, drop the magazine catch bar into the slot in the mag well. Flip the receiver over and slide the large spring over the threaded rod on the magazine catch. Compress the spring and thread the magazine release button onto the threaded post.

Once you start, you can push the button down using a brass punch, rotate the bar on the other side of the receiver, and turn it until the post sits flush with the magazine release button.

Test this with an unloaded magazine. The mag should lock in when inserted into the mag well and fall free when the button is depressed.

Fire Control Group / Trigger Installation:

The fire control group consists of the trigger assembly and the hammer assembly.

Start by securing the lower onto the action block.

Insert the larger side of the disconnector spring into the blind hole on the top rear of the trigger. The disconnector rides in the slot on the trigger with the hook facing forward. Install the temporary slave pin to secure the parts together.

Install the trigger spring with the spring legs facing forward, slide the crossbar under the front bar of the trigger, and bring the spring loops over the studs on the side of the trigger.

The loops on the hammer spring slip over the studs on the side of the hammer. The open end of the spring points toward the front, and the closed end faces the rear.

Refer to the image below to see the proper orientation for the trigger and hammer springs.

Credit: @apesvpply

Now carefully position the trigger assembly into the lower receiver until the holes in the trigger line up with the pin holes in the receiver.

The trigger pinhole is the hole towards the rear of the frame. Now insert one of the hammer trigger pins into place from the left side of the receiver. Smooth end first. This action will push out the slave pin and secure the trigger into the receiver.

Now position the hammer into the receiver with the legs of the spring resting on the pin, holding in the trigger. Line up the pin holes again and tap the hammer pin into place with your hammer or mallet.

Selector Switch / Safety:

Slide the safety through the sector switch hole near the rear of the receiver. Place the selector switch into the “Safe” position, then turn the frame upside down. Drop in the safety detent into the small hole near the pistol grip provision. The safety selector is held in place with a spring that rests inside the pistol grip.

We will complete the safety installation in the next step.

Pistol Grip:

Tap the safety spring in Aeroshell grease, then insert the greased end into the hold on top of the pistol grip. The grease will hold the spring in place when we flip the grip upside down for installation.

Turn the grip upside down, aligning the spring with the safety detent. Install the grip screw and tighten it until it is snug.

Now your selector switch and pistol grip are successfully installed. Function check the safety can be actuated into the “Safe” and “Fire” positions.

Rear Takedown Pin:

The rear takedown pin is much easier than the front pin. Slide the pin into the closed position, and drop the detent into the hole at the back of the receiver.

In the next step, we will finish the takedown pin installation during the buffer tube installation.

Buffer Tube:

Start by screwing the castle nut onto the buffer tube, then slide the endplate on behind it.

Now drop the spring and buffer retainer pin into the hole in front of the buffer tube extension. Screw the buffer tube into the receiver until it touches the buffer retainer.

Drop the takedown pin detent spring into the hole on the rear of the receiver. This will complete the rear takedown pin installation from the previous step.

Push the retainer down and rotate the buffer tube until it is in its correct orientation, with the endplate and adjustable stock notches facing down.

Capture the detent spring by pushing the endplate flush into place on the rear of the receiver. Hand-tighten the castle nut to lock the assembly into place. Now torque the castle nut to the manufacturer’s specification, usually about 40 ft/lbs.

Slide your buffer assembly into the buffer tube, we’re using the JP Silent Capture Spring as it allows us to change out the springs to fine-tune our system, and the guide rod eliminates” Twang” noises from the spring.

Your lower receiver is assembled. Nice work! 

The lower receiver is more involved than the upper, so the remainder of this walkthrough will be a breeze.

AR15 Upper Receiver Parts

• Stripped Upper Receiver
• Barrel
• Barrel Nut
• Gas Block
• Gas Tube
• Handguard
• Ejection Port Cover
• Forward Assist
• Bolt Carrier Group

Assembling an AR-15 Upper Receiver

The upper receiver of an AR 15 hosts the barrel (typically a 16-inch barrel), handguard, and gas system primarily. These parts can be assembled quickly and easily, but it is crucial to ensure they are installed correctly to avoid reliability issues.

Ejection Port Cover:

The ejection port cover assembly consists of the ejection port cover, a long roll pin, a snap ring, and the ejection port cover spring.

Firstly, install the snap ring on the groove in the pin.

Now start the pin in the ejection cover pinhole, then slide the ejection port in line with the pin and push the pin in slightly to retain the ejection port cover.

Now drop in the spring to align with the pin, ensuring the legs are facing upwards on both sides. Continue seating the pin until it stops against the snap ring.

Barrel:

The barrel is the heart of the rifle. To install it, simply slide the chamber end of the barrel into the barrel extension on the front to the upper receiver. Ensure the alignment pin aligns in the notch at 12 o’clock on the receiver extension.

Tap the back end of the upper against your workbench to ensure the barrel is fully set into the upper receiver.

Now apply a thin coat of Aeroshell to the barrel nut threads and thread on the barrel nut by hand. You’ll want to “season” the threads on the barrel nut, torquing it to 35 ft/lbs, loosening it, and repeating this step 3 times.

This will ensure the nut does not move once it’s torqued to its proper spec. After seasoning the threads, torque your barrel nut to the manufacturer’s spec.

Your barrel is in and soon will be ready to send bullets down range reliably and accurately with your 5.56 suppressor!

Gas Block:

The gas block allows gas from the barrel to circulate back to cycle the bolt. We chose the JP Adjustable Gas Block as it perfectly allows us to dial in the gas for any ar-15 suppressor we attach to our rifle.

Firstly, we must attach the gas tube to the gas block before installing it on the barrel. An armorer’s bench block gives you a stable surface to install this part easily, but it is not required. Insert the gas tube into the hole on top of the gas block and align the pin holes. Ensure that the gas tube is in the correct orientation. The tube should bend upwards for reference.

Using a roll pin starter punch, drive the roll pin through the pinhole on the gas block and tube. Tap the roll pin with your brass punch and hammer until it is flush with the gas block.

Now we can install the gas block assembly onto the barrel.

Slide it down the barrel to the gas port drilled on top of the barrel. Ensure the gas port on the barrel is properly aligned with the port on the gas block.

Tighten the gas block screws to the recommended spec, usually around 15-inch pounds, NOT foot-pounds.

Now that the gas block and tube are secured to the barrel, our rifle will function reliably, and we’re almost done with the build.

Handguard:

Every handguard has a slightly different installation method and a different way that they lock onto the barrel nut. Refer to your owner’s manual for your specific handguard’s proper installation and torque specs.

Forward Assist:

The forward assist is quick and easy.

Just get the roll pin started in the forward assist provision on the upper receiver using your roll pin starter punch, then slide the spring over the forward assist.

The hinge should be positioned to bend to the right when looking at it (towards the ejection port.) Push the forward assist all the way in, then finish tapping in the roll pin with your hammer and punch.

Charging Handle:

The charging handle slides into a channel at the rear of the upper receiver; insert the charging handle with some upwards pressure, and it will seat itself correctly into the charging handle channel.

Gas-defeating handles like the Radian Raptor SD are ambidextrous and work great for suppressed builds as they help eliminate gas to your face as you shoot.

Bolt Carrier Group:

With the charging handle pulled about halfway back, you can simply slide the bolt carrier group (BCG) into the rear of the upper receiver.

This Aero Precision PRO BCG is nitrite finished to ensure it runs, even while dirty, for maximum reliability.

Assembling an AR15:

Congratulations, your custom AR15 is finished!

You can attach the upper and lower using the takedown pins and function check all the components together.

Now you can outfit your new AR15 silencer ready rifle with parts and accessories you want to customize your new rifle:

• Silencer
• Stock
• Foregrip
• Iron Sights or Optic
• Weapon Light

We chose to outfit ours with a SureFire Scout Light, Armageddon Gear suppressor cover, and a Vortex Holographic sight.

Don’t forget you can watch our How to Build an AR15 for Suppressors video for a more in-depth look at some of these parts, and you can always find your next or 10th suppressor at Silencer Shop.