How To Build An AR-15 Rifle(Complete Lower and Upper Receiver Build Guide)

Can I build my AR-15? Yes, you can! As a matter of fact, it’s legal to build your own AR-15 but within the guidelines provided by the ATF. Are you uncertain about how to do it? Well, take it easy. We have a complete guide on how to build an AR-15 Rifle.

However, it’s worth noting that there are essential factors to be considered before you embark on building your AR-15. They include the cost of tools and parts, time and laws, and regulations within your respective states or local authorities. 

What Tools Do I Need To Build My AR-15? 

When building an AR-15, you need specific tools to help you assemble the individual parts to come up with a complete gun. They are essential in such a process. Below is a list of what you need: 

  • Armorer’s wrench & wrench attachment 
  • Mallets 
  • Spare magazine 
  • A set of roll pin punch 
  • Screwdriver 
  • Ball-Pein hammer
  • An AR-15 vice block kit
  • Bench Vise
  • Adjustable wrench 
  • Lubrication 

What Parts Do I Need To Build My AR-15? 

How To Build An AR-15
How To Build An AR-15

A standard AR-15 can be divided into two primary components that hold other parts. They are the upper receiver assembly and the lower receiver assembly. Let’s look into the specific parts you will need while building your AR-15 Rifle. 

  • A stripped AR-15 Upper receiver. They are of various types and offer different applications. They include AR-15 A1, AR-15 A2, AR-15 A3, and AR-15 Flattop
  • A stripped AR-15 Lower receiver or an 80% lower. It’s worth noting that you will undergo a background check and pay an extra fee when you go for the stripped option. 
  • Barrel 
  • Bolt carrier group- it comes as individual parts or fully assembled 
  • Buffer, buffer spring & buffer tube
  • Handguard
  • Buttstock 
  • Grip
  • Iron sights 
  • Optical sight (optional)
  • Dust cover 
  • Trigger guard 
  • A muzzle device
  • Charging handle 
  • Barrel mug
  • Trigger 
  • Gas block, & gas tube
  • Washer 
  • Forward assist 
  • Other smaller and essential components include a magazine catch spring, magazine catch button, magazine catch, forward-assist spring, hammer springs, selector switch, bolt catch, hammer, and a hand trigger assembly. 

A Step By Step Guide On How To Build An AR-15 Rifle

Once you have the above tools and parts needed to build an AR-15, you need to follow a particular process for you to assemble a complete and functional firearm. Here is a simple step by step guide on how to go about the whole process. 

Ensure you have all your working table clean and all the parts well arranged. You group them into the lower receiver assembly, upper receiver assembly, and other smaller components. It helps you avoid confusion.

Upper Receiver Assembly

  1. Start by assembling your forward assist assembly, i.e., the forward assist, assist spring, and the roll pin.
  2. Insert the forward assist assembly into the upper receiver. Ensure it’s firmly fixed, and it moves with ease. 
  3. Proceed and install the ejection port cover on your upper. You will need a cover pin, a cover spring, and a cover pin snap for you to have a functional ejection port cover. 
  4. The next step is to assemble your bolt carrier group. It should consist of a bolt cam pin, a bolt carrier, a bolt, a retaining pin, and a firing pin. 
  5. Set up the charging handle and the bolt carrier assembly into the receiver. Start by installing the charging handle so that later you insert your bolt carrier assembly into the charging handle. 
  6. Place your barrel in the threaded part of the upper receiver. Also, attach the inner barrel nut and tighten the barrel. 
  7. You need to position the gas tube into your outer, inner, and upper using the three holes at the end. It will help you install your gas block. Now, slide your gas block on the barrel for you to thread the gas tube to the gas block. 
  8. Mount the handguard. Ensure it is firm but sliding freely. Also, inserting screws is vital for keeping the lock lever in a precise position. 
  9. The handguard provides a place to install other accessories. Add your iron sights, optical sights, flashlights, etc. 

Now that you have complete upper receiver assembly, you must continue to assemble the lower parts.

Lower Receiver Assembly 

  1. Start by fixing the trigger guard into your AR-15 lower receiver. You will also need a trigger guard roll pin and trigger guard screw at this stage. 
  2. Proceed and set up both the magazine catch and button. You will need a magazine catch button, magazine catch spring, and a magazine catch. After a successful installation, you need to do a magazine test. Insert an empty magazine to see if it seats correctly on the lower and if it’s released smoothly. 
  3. Install the bolt pivot pin 
  4. Next, fix the bolt catch 
  5. Assemble and insert the trigger group into the lower. Join together the hammer and trigger springs. Then install the disconnector & disconnector spring. Ensure all of these parts are well aligned. Continue and set up the trigger pin and hammer. 
  6. Then position the pistol grip and the selector switch into the lower.
  7. Fix the takedown pin installation at the back of the lower receiver 
  8. Finally, install your buffer tube into the rear of the receiver. Do not forget to fix a castle nut. Also, fit your buffer and buffer spring into the buffer tube. 

Now that you have a complete lower receiver assembly, you should join it with the upper receiver assembly. You will have a complete AR-15 gun. Proceed and insert a loaded magazine to see how it functions. 


Building an AR-15 Rifle is not a complex process as long as you have the right tools, parts, and a compressive guide similar to that provided above. However, use quality AR-15 parts and accessories if you want a quality rifle. 

Related Post

History of Colt AR-15 Rifle

Best AR-15 Triggers

Leave a Reply