If you’re looking for something more interesting than just buying a gun already assembled, making your own AR-15 might be for you. Even if you’ve never built a gun before, beginner kits can make the job pretty simple.
Building your own also gives you the option to customize it to your specifications. And you learn about the inner workings of your gun as you go.
Without any modifications, you can follow these basic instructions to learn how to build an AR-15. From there, you can switch out handguards, triggers, barrels, and more. Read on.
How to Build an AR-15
Consider the reason you want to build an AR-15. If you want to use it for competition, you need an adjustable gas block. You want to have as little recoil as possible, so you can shoot faster.
If you want it for home defense like most people, you don’t want the gas block dialed and finicky, because it won’t function with all rounds in all conditions. You want something that’s always going to shoot, not something optimized for competition.
If you’re hunting, you just need it to work. It doesn’t have to be that accurate or that fast, but maybe lightweight is a consideration.
Pay attention to your budget. These upgrades and modifications can add up fast. You can always make a little extra cash on the side to pay for your new hobby.
AR-15 Parts List
Most people buy a stripped lower receiver (need to buy this from a licensed gun shop, it’s the only serialized part), a lower parts kit, and a fully assembled upper. Some people build their own uppers, but it can be a hassle for a beginner.
It’s not advised to 3D print any parts because a home 3D printer isn’t robust enough. You’d need a high-quality, high-cost printer. But if you’re confident in your equipment, you could 3D print a stock and pistol grip.
Make sure your kit comes with a stock, or you’ll need to buy one. Strike Industries can help with all your firearm parts needs.
You’ll also need some tools. Here’s a full list of tools that are recommended:
- Armorer’s wrench and Torque wrench, or AR-15 combo wrench
- Drill bits
- Screwdrivers (full set)
- Molly grease (lithium grease)
- Gun oil
- Tapping oil
- Masking tape
- Fine sandpaper
- Safety glasses
- Touchup marker
- Punches (pin punches, drift punches, starter punches, long reach punches)
- Vices and action blocks (including hammer block)
- 1/4″ 28 tap and tap handle
If you have your tools, you’re ready to get started.
Inspect the lower receiver before you start assembling the gun. Look for burrs or defects in detent holes. If you find some chips or burrs, just a couple finger turns with the drill bit will remove these imperfections.
Install the Trigger Guard
Find the hole on the right side of the lower receiver where the trigger guard goes, and line it up. Use a fixture to support the ears while you insert the roll pin. Without support, the ears can break off, and you’d have to scrap the whole thing and start over.
Depress the spring-loaded detent, then slide the guard up and between the two ears. Now drive in the roll pin, using the roll pin starter punch to begin, then switching to a standard roll pin punch. Drive it the rest of the way into the hole so it doesn’t stick out either side.
Install the Mag Release
Action blocks are helpful during assembly. They’re the same size as a magazine, and they hold the lower so it doesn’t slip. If you are using one, use your vice to hold the action block and slip the lower onto it.
Stick some masking tape on the finish where the tools could slip and scratch the lower. You only need three parts for this step: the spring, release button, and body. Lubricate all parts before installing.
Put the spring in the body, then the release button. Use the wooden dowel rod to hold the button while you turn the screw threads from the other side.
Now that it’s installed, you have to push the button to release the mag from the action block. Test the mag release to make sure you did it right, and then you can take the tape off.
Install the Bolt Stop
Pay close attention during this part. It can be hard to get all four parts in the right place because they’re hard to access. You’ll be working with the release, the plunger, the roll pin, and the spring. Oil the pin and grease the spring and plunger before assembling.
You can use the action block again to hold the lower, and tape the finish again to guard against any scratches. Install the spring first in its hole, and add the plunger and the bolt stop.
Then you’ll need to stand the receiver up to install the hammer block, and it’s a good idea to clamp it down with a vice. Use extra long roll pin punches to finish the installation. You know it’s right if the pin sticks out a little on each side.
This part stops the forward movement of the bolt, so it’s very important to get it right. Double check your work using a magazine. Make sure the top of the follower grabs the bolt stop lip.
Install the Pivot Pin
Most brands have a detent to hold it in place. Put some oil on the pin and use grease on the detent and spring. It’s very helpful to have a pivot pin installation tool, otherwise, this job is almost impossible.
Put the tool through the loops, then put in the spring and the detent. Use a punch to depress the detent, and then turn it around until it catches. Now put the pivot pin in a little at a time, which will push the tool out the other side.
When it’s inserted all the way, turn the pin, and it will grab the detent.
Install the Hammer and Trigger
You have to install these together because they control the firing of the gun together. You’ll use the hammer, hammer spring, trigger, and trigger spring. You’ll also need the two hammer-trigger pins, along with the disconnector and disconnector spring.
First, you need to assemble the hammer and trigger, then you can put them into the lower receiver. Put the large end of the disconnector spring into the blind hole on the top rear of the trigger. The hook should face forward.
Use a slave pin to hold it in place. Make sure the disconnector turns without catching. Its movement should be smooth and fluid.
Hold the trigger spring with the legs to the front, and slip the crossbar under the front of the trigger. The trigger spring will loop over the studs on the trigger sides and the same with the hammer spring and hammer. The open end of the spring should be toward the front.
Now you can put the assembly into the lower. Use the action block again to hold the lower, while you line up the trigger assembly with the holes.
Put the end of the hammer-trigger pin without the groove into place from the left side. It’ll replace the slave pin. The legs of the spring should rest on the trigger, and you can hammer in the pin.
Cock the hammer to make sure it doesn’t hit the frame. Use a hammer block to test the firing assembly (dry fire) so you don’t damage the lower. Use a gauge to test the trigger pull.
Install the Safety and Pistol Grip
Just like with the hammer and trigger, you have to install these parts together.
Oil the safety, and grease the detent and spring. Make sure the hammer is cocked and you’re still using the hammer block. Put the safety in the lower from the left, then put the safety detent and spring in the hole in the pistol grip.
Line the spring up with the hole in the lower, and push it into place. Screw in the grip screw. Double check the safety to make sure it works.
Install the Buffer Tube
The buffer absorbs some of the kick and uses it to prep the gun for the next shot. You’ll need the buffer, buffer spring, buffer tube, retainer spring, and retainer.
Grease the retainer spring, retainer, buffer spring, and buffer. Place the retainer spring and retainer into position, then use a little Loctite on both sets of threads to glue the buffer tube to the lower. Screw it into position (hold the retainer down for the last few turns), using a wrench if you need to.
Slide the buffer spring into the tube, followed by the buffer (if you hear a rattle, it’s normal). The retainer should hold the buffer inside, and both the retainer and buffer should move without catching.
Install the ButtStock and Takedown Pin
Oil the takedown pin, and push it into the lower from the right side. Insert the detent and then the spring from the rear end. They’ll stick out a little.
Slide the buttstock over the buffer tube, without bending the spring. Now fasten the butt plate to the stock.
Combine the Receivers
The upper and lower receivers are held together by a pivot pin. Cock the hammer and turn the safety on. Place the receivers together, aligning the pivot pin bosses, the push in the pivot pin.
You can tighten the fit with a wedge under the takedown pin if you like. Insert the charging handle and bolt assembly, pivot the upper assembly back, and hold it down with pressure on the carry handle.
You’re all finished!
Now you know how to build an AR-15. Follow these steps, and you’ll be able to assemble the whole gun.
It’s fun to learn a new hobby like gunsmithing. The inner workings of machines are intricate and fascinating.
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