The AR15 rifle is the most popular among US citizens for many reasons.
The wide specter of customization options makes it so popular as even the fact that you can build your own AR-style rifle at home.
Let’s see how you can build your rifle at home.
Table of contents:
Why Should You Build AR15
Buying or building AR15 - each one of them has its pros and cons. However, this time we will focus on the benefits of building your AR15 at home.
- Customization: Most already-made AR15 rifles have defined specifications which in some cases may not suit your need or may not be what you’re looking for. Customizing gives you all the power to choose each component separately.
- Good feeling: Building your own fully functional AR15 rifle will surely make you feel great. And when you shoot your first round you’ll experience that “It’s alive” moment.
- More knowledge: Building your rifle will get you more insight and knowledge about how your rifle works. You’ll understand why each part is made in that way and how it behaves when you pull a trigger.
- Less cost: Not strictly defined, but depending on the parts you choose for your rifle, you can save money and still make a high-quality rifle for yourself. However, note that each market has its own more or less pricey products. The same goes for AR15 rifles.
AR15 Parts Needed
As we explained in our AR15 guide article recently, the rifle is made of two main components: upper receiver and lower receiver. If you want to learn more about each part, visit the link above.
Upper Receiver Parts
The upper receiver is in charge of the rifle’s operation. It includes these parts:
- Barrel
- Gas block
- Gas tube
- Handguard
- Bolt carrier group
- Charging handle
- Forward assist
- Ejection port cover
Lower Receiver Parts
The lower receiver is a vital part of your rifle as it contains parts like magazine catch and trigger group. Parts included in the lower receiver:
- Trigger assembly
- Trigger guard
- Bolt catch/release
- Mag catch/release
- Safety selector
- Takedown pins
- Grip
- Buffer tube
- Buffer and spring
- Buttstock
Now, these are all parts you would need to assemble your rifle. You can take a shortcut (boring) and go straight to the store and buy one complete lower and complete upper receiver. But that won’t improve your knowledge of your rifle.
Before You Begin
You decided to build AR15 and got all parts from the above and that’s great. But there are still some things to prepare before you start assembling all parts.
- Safety first: This is the most important one. Make sure that you’re wearing protection glasses while assembling all parts. There are lots of tiny parts and springs that can jump all over your workshop. You don't want any of these fellas hit you in the eye.
- Gather necessary tools: You can’t build anything without proper tools. Especially when you have lots of tiny parts to assemble.
- Prepare your surroundings: Yes, this may sound strange, but you don’t want to lose any of those tiny parts and springs in the room. This is not a must, just a friendly recommendation to avoid losing tiny parts.
Tools You’ll Need
- Armorer’s wrench.
- Torque wrench.
- Punch set.
- Vise and vise block.
- Hammer.
- Screwdrivers.
- Upper and lower receiver vice blocks.
- Gas block and gas tube alignment tools.
- Barrel nut wrench.
- Barrel vise.
- Cleaning tools.
Upper Assembly
Now, let’s go through the step-by-step assembly process of the upper receiver.
Tools and parts needed:
- Stripped upper receiver
- AR-15 barrel
- Barrel nut
- Gas tube
- Gas block
- Gas tube roll pin
- Handguard or free-float rail (if applicable)
- Forward assist assembly (optional, not all AR-15s have this)
- Ejection port cover assembly (optional, not all AR-15s have this)
- Muzzle device (flash hider or muzzle brake)
- Crush washer or peel washer (if applicable)
- Armorer's wrench or multi-tool with barrel nut wrench and other necessary tools
- Torque wrench
- Upper receiver vise block or vise with padded jaws
- Pin punches and hammer
- Anti-seize grease or thread locker (optional but recommended)
First, prepare the upper receiver by installing the forward assist assembly and the ejection cover.
Next, install the barrel following these steps:
- Insert the barrel extension into the upper receiver.
- Apply a small amount of anti-seize grease or thread locker to the barrel nut threads.
- Hand-thread the barrel nut onto the upper receiver.
- Use the armorer's wrench or barrel nut wrench and torque wrench to tighten the barrel nut to the specified torque value (typically around 30-80 ft-lbs, depending on the barrel nut design and brand).
Install the gas tube and gas block:
- Slide the gas tube through the gas port in the barrel and into the gas block.
- Secure the grass tube roll to the gas block.
Install a muzzle device:
- Attach a muzzle device to the barrel.
- Use a wrench to torque the muzzle device.
Attach the handguard:
- Slide the handguard over the barrel.
- Align it with the upper receiver.
- Tighten the mounting screws (or barrel nut).
Finally, add bolt carrier group and charging handle:
- Slide the BCG into the receiver.
- Slide the charging handle into the channel at the rear of the upper receiver.
- Slide it until it locks into the bolt carrier group (BCG).
Lower Assembly
The main block for rifle operation (upper receiver) is done. Now, let’s see how to assemble the lower receiver in order to enable the rifle to function properly.
Tools and parts Needed:
- Stripped lower receiver
- Lower parts kit (LPK) with trigger assembly, hammer, safety selector, etc.
- Buffer tube assembly (buffer tube, buffer spring, buffer, castle nut)
- Pistol grip
- Stock or buffer tube brace (for a pistol build)
- Magazine catch assembly
- Bolt catch assembly
- Pivot pin, takedown pin, and detents
- Trigger guard assembly
- Allen wrenches or punch set
- Armorers wrench or multi-tool
- Rubber or non-marring hammer
- Lower receiver vise block
- Roll pin punch set
- Vise with padded jaws (optional but helpful)
Start by inserting the pivot pin and takedown pin. This will secure the detents in place.
Next, install the trigger guard. Attach the trigger guard assembly to the lower receiver using the roll pin. Use a roll pin punch to tap the roll into place.
Install the magazine catch assembly:
- Insert the magazine catch into the lower receiver from the outside.
- Secure it in place using the magazine catch spring and button on the interior side of the receiver.
- Use a punch to push the roll pin through the receiver securing the mag catch in place.
Install the bolt catch assembly:
- Insert the bolt catch into the left side of the lower receiver.
- Place the bolt catch spring and plunger into their respective positions within the receiver.
- Align and insert the bolt catch roll pin to secure the bolt catch in place.
Install the trigger assembly:
- Insert the trigger, hammer, and trigger spring into the lower receiver.
- Attach the disconnector spring to the trigger and hammer.
- Place the hammer spring and hammer pin in their respective positions.
- Insert the hammer and trigger pins to secure the trigger assembly in place.
Install the safety selector:
- Insert the safety selector detent and spring into the lower receiver.
- Place the safety selector into the receiver and ensure it properly engages with the detent.
- Rotate the selector to test its functionality.
Attach the pistol grip:
- Connect the pistol grip to the lower receiver using the screw.
- Tighten the screw until snug, but avoid over-torquing.
Install the buffer tube assembly:
- Slide the buffer tube into the rear of the lower receiver.
- Threat the castle nut into the buffer tube and tighten it.
- Use the armorer's wrench to properly torque the castle nut to the specified value (for example, this value can be from 40 to 80 ft/lbs).
- Insert the buffer spring and buffer into the buffer tube.
Attach the stock or buffer tube brace:
- Slide the stock into the buffer tube and secure it in place (stock).
- Attach the buffer tube brace to the buffer tube (for AR pistol).
Of course, in the end, check the functionality of the rifle.
Attach Upper and Lower Receiver
By now you should have completed both upper and lower receiver assemblies. Let’s see how to connect those two now.
Step by step:
Step 1 - Safety check: make sure the upper and lower receiver are unloaded. Remove the mag.
Step 2 - Align receivers: align the front and rear takedown pins of the lower receiver with the proper holes in the upper receiver.
Step 3 - Insert front takedown pin: insert the front takedown pin first. Push it through until it locks into place, securing the front of the upper receiver to the lower receiver.
Step 4 - Insert rear takedown pin: once the front takedown pin is in place, push the rear takedown pin through the lower receiver until it locks into the rear hole of the upper receiver.
Step 5 - Check fit: after inserting both takedown pins, ensure that upper and lower receivers fit together with minimal movement.
Step 6 - Test functionality again: with the upper and lower receiver properly mated, perform a function check to ensure everything is working. Check the safety selector, trigger, mag release, and bolt catch to ensure they work as they should.
Step 7 - Enjoy your build. That’s it!
Most Common Specs
If you’re not sure what parts to buy for your first (or next) build, we will list the most common configurations for a few different calibers.
5.56mm AR-15 Specs
- Caliber: 5.56x45mm NATO.
- Barrel Length: 16 inches.
- Gas System: Direct impingement.
- Handguard/Rail: Free-floating handguard or rail system that allows attachments like grips, lights, and optics.
- Magazine Capacity: Standard 30-round mag.
- Muzzle Device: Flash hider or muzzle brake to reduce muzzle rise and recoil.
- Upper Receiver: Flat-top upper receiver with M-LOK or Picatinny rail sections for mounting optics and accessories.
- Lower Receiver: Typically made of aluminum and may have a mil-spec buffer tube for the stock.
- Stock: Collapsible or fixed stock, depending on the intended use.
9mm AR-15 Specs
- Caliber: 9x19mm Parabellum (9mm Luger).
- Barrel Length: 12 inches.
- Gas System: Blowback-operated.
- Handguard/Rail: Free-floating handguard or rail system.
- Magazine Capacity: 10 to 33-round mags.
- Muzzle Device: Threaded muzzle to attach compensators or suppressors.
- Upper Receiver: Flat-top design for optics and accessories.
- Lower Receiver: Aluminum, designed to accommodate Glock magazines too.
- Stock: Collapsible stocks or pistol brace options.
300 Blackout AR-15 Specs
- Caliber: .300 AAC Blackout (Also known as 300 BLK or 7.62x35mm).
- Barrel Length: 9 to 10 inches.
- Gas System: Pistol-length or carbine-length gas system.
- Magazine Capacity: Standard 30-round mag.
- Muzzle Device: Muzzle brake or flash hider.
- Upper Receiver: Flat-top design with Picatinny or M-LOK rail sections.
- Lower Receiver: Similar to the 5.56mm AR-15 lower receiver, with adjustments for the specific caliber and magazine.
6.5 Grendel AR-15 Specs
- Caliber: 6.5 Grendel.
- Barrel Length: 18 inches.
- Gas System: Rifle-length gas system.
- Magazine Capacity: 10 to 30-round mags.
- Muzzle Device: Muzzle brake or flash hider.
- Upper Receiver: Standard AR-15 upper receiver with Picatinny or M-LOK rail sections.
- Lower Receiver: Adjusted for the specific caliber and magazine.
6.8 SPC AR-15 Specs
- Caliber: 6.8 SPC (Special Purpose Cartridge).
- Barrel Length: 16 inches.
- Gas System: Mid-length gas system.
- Magazine Capacity: 10 to 30-round mags.
- Muzzle Device: Muzzle brake or flash hider.
- Upper Receiver: Standard AR-15 upper receiver with Picatinny or M-LOK rail sections.
- Lower Receiver: Modified for the specific caliber and magazine.
Conclusion
Well, that’s it for now. If however, you want to learn more about the AR-15 platform before diving in into making your own complete rifle, check our article How To Build AR15 Rifle At Home.
Additional Reading
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