Building Your Own AR-15: Complete Checklist
AR Building is More Common Than You Think
You don’t need to have military training to build an AR-15. In fact, it’s hobby that has grown a lot in popularity, making the AR-15 is the most popular sporting rifle in the U.S. The endless combinations of parts and aftermarket upgrades is so vast that it can be intimidating for a beginner.
AR enthusiasts can build AR set ups for different applications – CQB, hunting, long range precision, home defense, and others.
Believe it or not, gunsmithing skills are not required, only a few basic tools. Building your own AR piece by piece is an unspoken skill every capable guy should have. This page is meant to be a checklist of all the parts required to assemble a complete and functional AR.
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Retailers for AR-15 Parts
What’s great is that all of these components can be purchased online from various retailers at great deals. There are literally always new deals popping up around the web, so if you can put in the time to look it will save you cash. Most often you can build your own unique AR at a lower cost than buying a fully assembled gun.
The most popular sites to shop for parts are:
Palmetto State Armory
A note about FFL requirements – at the time of writing this, the lower receiver is required to be shipped to a licensed FFL dealer near you where you must complete a background check in order to pick up the part. The lower receiver cannot be shipped to your home.
Another part that is regulated is suppressors which require additional paperwork. For now, it’s a good idea to get the fundamentals of assembling an AR before venturing into suppressors. Besides, that will likely be the last item you will buy once completing an AR build.
The best place to start is learning about your state’s specific gun laws. For example, there are laws in certain states around pistol grips, barrel lengths, and magazine capacity.
You are explicitly encouraged to do your research.
Disclaimer: You are responsible for your own decisions. This website or its owners are not liable for any damages resulting from your actions.
ARs come in several different calibers. The most popular is the 5.56 NATO because of its availability, low cost, and performance. There is also 300 Blackout that tends to be used with suppressors and pistol ARs. Big game hunters tend to seek out the less common calibers such as 6.5 Grendel, 350 Legend, and 450 Bushmaster.
.223 Wylde – essentially this is the type of barrel allows you to shoot 5.56 and .223 rounds interchangeably.
AR-10 – AR’s that are chambered in .308 and come with longer, heavier barrels.
Pistol Caliber Carbines – some AR’s are modified to shoot 9mm or 45 ACP with Glock magazines.
As you can see there are lots of directions to go when building ARs. For first timers, it’s best to just start with the 5.56 caliber. Keep it simple for now.
Having all of these tools certainly makes the assembly jobs easier, but not all are absolutely required. If you truly are building an AR piece by piece then its a good idea to have all of these tools. In the long run you will have an easier time reconfiguring AR setups and building more guns.
- Armourer’s wrench – very useful for working on barrels, buffer tubes, and muzzle devices.
- Allen wrenches/Hex keys – mostly used for installing accessories on rails and hand guards.
- Vice block – holds the lower in a comfortable static position.
- Bench block – very useful for working on installing small parts and pins.
- Punch and hammer set – needed for assembling small parts to the lower receiver.
The lower is the main component that brings together the stock, grip, magazine port, and trigger as the main part of the gun held in your shooting hand next to your cheek. These can be purchased as a complete lower assemby or as these individual parts.
Note – Lower receivers are the serialized component of an AR. Whether you buy a fully assembled lower or just the stripped lower receiver itself, you will need to ship to an FFL where you will complete the background check at pick up.
All other lower parts can be ordered and shipped normally.
- Lower receiver (FFL required)
- Trigger assembly
- Safety selector assembly
- Magazine release
- Bolt catch
- Buffer tube
- Buffer spring
- Buffer retainer
- Buffer retainer spring
- End plate
- Castle nut
- Takedown pins
- Stock or pistol brace
The upper is the combination of the barrel, hand guard, and housing around the bolt. This is the basically the front half of the gun. The average Joes like to order these as a complete upper assembly to avoid dealing with the barrel install. In reality it isn’t all that difficult as long as you have a large wrench or armourer’s wrench to match the barrel nut.
Most of the “fun” parts are attached to the upper like the optics, muzzle devices, grips, lights, and other gadgets.
Note – Choose a barrel with a 16 inch length. Anything shorter is considered a pistol or short-barreled rifle (SBR). Pistols are legal, but additional paperwork and background checks are needed for an SBR. To avoid trouble with the ATF stick to the 16 inch barrels for now. As you learn more about the legal nuances of pistol braces and barrel lengths you can venture that direction.
All of these parts can be ordered and shipped normally.
- Upper receiver
- Forward assist
- Dust cover
- Bolt carrier group
- Charging handle
- Barrel nut or Delta ring
- Barrel (16 inch)
- Gas block
- Gas tube
- Muzzle device (flash hider or muzzle brake)
- Iron sights
AR15 Styles: To Each Their Own
People build all types of AR15 patterns. Depending on what you plan to use your AR for there are various parts and accessories you can put on it to change the design and size. The AR15 platform is great because you can make it your own and switch it up until you find what works for you. Below are some common “types” of AR15 configurations:
AR Space Gun
AR Truck Pistol
Other Optional Accessories
- Folding backup iron sights
- Sling attachement points
- Offset rails
- Extended mag release
- Pistol grip rubber cap
- Rail covers
- Forward or angled grips
- Magwell grip
- Optic magnifier
- Carrying case
Most of the assembly is pretty straight forward and actually pretty easy. Once you do install a piece the first time you will realize how it is not terribly complicated.
The assemblies below tend to be the more tricky ones the first time doing them:
- Installing the trigger assembly from scratch – unless you get a “drop-in” trigger that literally just drops in to the slot.
- Attaching the barrel to the upper receiver because you will need the armourer’s wrench. And then installing the gas block assembly because you need to line up the hole in the top of the barrel to the inside of the gas block.
- Choosing between two types of hand guards, ‘drop-in’ and ‘free float’. The free float tends to be the easier type to install and usually has more attachment slots for lights and grips up at the front end.
All of this may sound complicated, but really you just need to do it once to learn it. Written text is not the best way to show how it’s done, especially for visual learners. In this day of technology just look up a Youtube video to see how a certain step is done. There are plenty of tutorials online.
Mistakes to Avoid
Once you have completed your build, make sure you use proper protection when testing firing the first rounds. It’s a good idea to go to your local range and ask for someone to inspect your firearm before shooting.
To avoid catastrophic damage and/or injury, here are some mistakes to make sure you are not making.
- all parts are secure
- moving parts are lubricated (bolt carrier group)
- shoot only the caliber of ammunition that matches your barrel
- muzzle device is properly oriented and tightened
As always be sure to follow all basic firearm safety rules.
Now that you have a fully functional firearm, you will probably want to experiment with different setups of optics, rail attachments, muzzle devices, and maybe a paint job. You’re going to need plenty of ammo. Also you now have the knowledge to go build another one.