Building an AR-15 Step-by-Step, Part 1: The Lower Receiver
These seven videos of a custom .223 Wylde rifle build will teach you how to install every component of an AR-15 lower.
THE BENEFITS OF BUILDING AN AR-15 are numerous. There’s the satisfaction of having the exact parts you want, from the barrel to the takedown pins. There’s the ease of purchase. Once you get a stripped lower from an FFL, all the other components can be bought without a background check at a brick-and-motor gun shop, or online.
There’s the learning curve. By the end of a building project you’ll know the AR platform inside and out, and will be able to apply this knowledge to building more rifles, or improving the accuracy and performance of factory guns.
For the first Range365 AR build project, we opted to assemble an accurate, .223 Wylde-chambered, minimalist AR-15 in Range365 blue and white with the finished rifle able to serve as a show gun at events, a hyper-accurate range toy, and as a tricked-out predator rifle when duty called. (For those who don’t know, “.223 Wylde” is a short way of saying it can handle both .223 and 5.56 ammunition)
The project began when we decided to replace the barrel on a perfectly competent Bushmaster Minimalist SD. That Krieger barrel swap proved such a success—and a fun learning project—we broke down the rifle and built it up again from scratch.
What follows is a video guide on how to build your own AR-15 at home with basic tools.
Any reasonably mechanical person should be able to follow this guide and have a finished, safe, and accurate rifle. To ensure our advice and guidance was as accurate as our barrels, we enlisted the help of Valley Armament in Sayre, PA—a LGS in Pennsylvania’s northern tier that builds multiple AR-15s a week for clients who demand custom treatment.
- Orientation. For our purposes, “left” and “right” refer to sides of the rifle from the shooters perspective when the rifle is pointed forward.
- Work Surface. Make sure you have a clean well-lit area to work. Try our Yoga Mat trick. A drop cloth under your work area saves time hunting for dropped roll pins, too.
- Tools. It doesn’t take tons of tools to build an AR, but these tools are worth the investment.
- Safety. Eye protection is highly recommended. Springs especially like to fly.
|Lower Receiver||Bushmaster ACE Skeleton Stock Lower|
|Parts Kit||Bushmaster XM-15 Lower Receiver Parts Kit|
|Extra Parts||2A Armament Carpet Kit|
|Pistol Grip||Magpul MOE SL Grip|
|Selector||Radian Competition Talon|
|Magazine Release||Odin Works XMR 2 Extended|
|Trigger||Timney Triggers AR TARGA 2-Stage|
|Take Down Pins||2A Armament AR-15 Titanium|
|Buffer Tube||2A Armament Buffer Tube Assembly (fluted)|
|Buffer Assembly||KynSHOT Hydraulic Buffer w/ JP Spring|
|Buttstock||Magpul MOE SL Carbine Stock – Mil Spec|
How to Install a Magazine Release on an AR-15
The magazine release is a good place to start assembling a stripped lower. By starting here there’s plenty of room for the mag catch bar to clear the bolt release on the left side of the lower. Here we installed an Odin Works XMR, but the process is the same for most mag drop buttons.
To start, insert the post and catch bar into the left side of the lower, and the mag button and spring on the right.
With a dowel or large punch, depress the spring and button, so the post stands proud on the left side, then screw the catch bar clockwise into the threaded button.
Once installed, it will capture the post and spring, and on the XMR the mag drop button can be screwed down on the right side of the lower.
How to Install the Bolt Release on an AR-15
First, start the bolt release roll pin. Pro tip from Matt at Valley Armament: get a piece of foam pad, like what comes in a scope box, and lay it on the left side of the upper while you hammer the bolt release pin. This will prevent marring the lower.
Next, drop the spring and plunger in the detent hole. Now line up the paddle with the roll pin holes depressing the spring and plunger, then capture it in place with a small Allen key.
Carefully hammer in the roll pin.
How to Install the Front Takedown Pin on an AR-15
Do yourself a favor and get a front takedown pin pivot tool. It’s not needed, but makes an otherwise trying job quick and easy.
We used 2A Armaments Titanium Takedown Pins. Matt got them in in less than a minute, as you can see in the video. Simply insert the tool in place of the pins, drop in your spring, roll the tool to capture everything, then careful slot in the actual takedown pin.
How to Install an AR-15 Trigger
A good trigger is an essential part of an accurate rifle, so with all our R365 AR builds we went with Timney Triggers. For this .223 Wylde, we went with the short-pull 2-Stage Targa set at 2 pounds in the first and second stage. A
s you can see in the video, installing a drop-in trigger like this one on a stripped lower is just a matter of dropping it in, lining up the holes, and placing your pins. A mil-spec trigger comes in two parts and is slightly more complicated. For anything but the lowest-budget build, go with a drop-in trigger.
How to Install an AR-15 Safety Selector and Pistol Grip
For all the R365 AR builds we went with ambidextrous Radian Talon selectors. For this .223 Wylde and the 6mm Creedmoor we used Magpul furniture.
The detents that work the selector are held in place by the grip on an AR-15, so they need to be installed together.
Simply slot the selector and attach both levers, if it’s an ambidextrous assembly.
Next, drop the plunger in the lower and the spring in the grip. Marry the two when sliding the grip in place, then tighten it down via the bolt, which is hidden in the grip itself.
How to Install an AR-15 Buffer Tube, Rear Takedown Pin, and Buffer Assembly
First, put your end plate and castle nut on the buffer tube, and screw it loosely into the lower. Next, install the rear takedown pin. Then drop in the takedown pin detent and spring, then cover and capture with the end plate.
Holding the end plate in place, drop in the buffer spring and detent, and line up the buffer tube by twisting it down until it captures the plunger. Once everything is lined up, torque the castle nut down to 35- to 40-foot pounds.
For the buffer assembly, we installed a KynShot package from Nokick.com. It advertises as the softest running buffer available for an AR-15, and after a few weeks of shooting this show pony, we believe it. It’s also extremely quiet. No pongo-stick spring clanging like with mil-spec buffers.
How to Install an AR-15 Buttstock
Most collapsible buttstocks have a lever or pin that’s pushed up, allowing the operator to adjust the stock to their personal length of pull. Installing a buttstock is a simple matter of pulling that lever or pin in the opposite direction, which disengages the slide lock, and running it over the buffer tube.
If you can’t quite get it, check out the video for a cool tip from Matt on how to get a use a small Allen key to break the lever free.