5 Best AR-15 Build Kits

Are you looking to build your custom AR-15?

Have you started looking at parts, but you’re not sure where to begin?

Would you like to finish an 80% receiver for your rifle?

Then what you need is an AR-15 build kit. There are a lot out there, so you need to be careful that you buy exactly what you need.

That’s why we went through many options and narrowed them down to our favorites.

Read on for more information about our picks for the best AR-15 build kits.

Product Our Rating

Review Of The Best AR-15 Build Kits

best ar 15 build kits

In this section, we go into detail on what each build kit involves and the features the companies put into them. Keep in mind the features and your purpose for buying one, and you should have no problem making a choice.

Brownells – AR-15 Receiver Set W/lower Parts Kit & Stock

This receiver set by Brownells is the most expensive option on the list, but it’s a complete set of all the parts you need to complete your AR-15 build.

The kit includes an Anderson Manufacturing 80% finished lower receiver. The lower is made from aluminum for lighter weight but durability.

The lower also has a black anodized finish to provide some more protection from corrosion.

At 80%, you will need to install fire control/trigger group milling, trigger pin, hammer pin, trigger slot, and the safety selector hole.

The upper assembly is made from Brownells and features a 16” barrel with a 1:8” twist that’s chambered for the 5.56 NATO.

With an A3 upper receiver made from aluminum and 10” M-LOK rail handguard, you get a quality upper with the ability to add accessories onto it.

The buttstock that also comes with it has an adjustable pull, fiberglass-reinforced polymer, and recoil absorption mechanisms.

This all seems like a lot, but Brownells also includes all the mil-spec parts and instructions you need to finish the lower and assemble all the parts.

The user experience boils down to this:

Positives Recap for This Product

  • A ton of parts and tools included with this kit
  • Looks tactical and stylish
  • Once assembled, the rifle shoots accurately and consistently
  • Easy to finish and assemble
  • Durable materials and design

Negatives Recap for This Product

  • Higher cost
  • The lower receiver is not mil-spec

PSA AR-15 Magpul CTR Lower Build Kit

This build kit by Palmetto State Armory includes everything you need to finish and assemble your lower receiver at an affordable price.

When you buy an 80% lower receiver separately, it isn’t finished and requires more parts. This kit completes the lower you bought.

All the parts included in this low kit are mil-spec, which means that they should fit with little difficulty any other mil-spec parts including upper receivers.

With the purchase of this kit, you get a CTR stock, MOE grip, and MOE trigger guard. These are in the Flat Dark Earth style, which is very much like the style the Army may use.

You also get their Palmetto State Armory Lower Parts Kit that finishes the lower you purchase.

Pro-tip: Get a lower receiver that’s also mil-spec. This makes it easier to match up and finish.

You also get a 6 position mil-spec buffer tube with this kit. A lot of great features to finish the lower receiver you’re working on.

Customers who used this product had this to say:

Positives Recap for This Product

  • Affordable price
  • Parts and kit fit easily with mil-spec lower receivers
  • Quality and durable parts
  • The finish looks great and offers protection from corrosion

Negatives Recap for This Product

  • No consistent complaints were found

Related: Best AR-15 Muzzle Breaks 

CMMG – AR-15 Lower Gunbuilder’s Lower Parts Kit

The CMMG kit comes with only the parts needed to finish the lower receiver you bought separately. As such, it’s extremely affordable.

The kit contains the following parts:

  • Takedown pin
  • Receiver pivot pin
  • Takedown pin detent (2)
  • Takedown pin detent spring (2)
  • Hammer and trigger pin (2)
  • Safety selector
  • Selector detent
  • Magazine catch
  • Magazine catch spring
  • Magazine release button
  • Bolt catch
  • Bolt catch plunger
  • Bolt catch spring
  • Bolt catch spring pin
  • Buffer retainer
  • Buffer retainer spring

It does not include the trigger, grip, and trigger guard.

This may be the build kit for you if you’re looking to fully customize your AR by buying every part separately.

The user experience boiled down to the following:

Positives Recap for This Product

  • Good quality parts
  • Excellent instructions
  • Tools help with other receivers
  • Some like the no grip and trigger because they want more customization control
  • Low price

Negatives Recap for This Product

  • Doesn’t come with grip or trigger

Related:Best AR-15 Angled Foregrips 

Brownells – AR-15 Lower Receiver Completion Kit

Brownells’ lower receiver completion kit is the build kit for those who still want to purchase their receiver to finish, but don’t want to also purchase separate grip and trigger assemblies.

This medium-priced kit comes with lower receiver parts and tools needed to finish an 80% lower. This includes:

  • Trigger spring
  • Trigger pin
  • Hammer spring
  • Hammer pin
  • Disconnector and spring bolt catch
  • Bolt catch plunger
  • Bolt catch spring
  • Bolt catch roll pin
  • Selector
  • Selector detent
  • Selector detent spring
  • (2) takedown detents and springs
  • Pivot pin
  • Rear takedown pin
  • Buffer retainer and spring
  • Magazine catch, button, and spring

It also comes with the trigger, trigger guard, and pistol grip.

All of the parts are made by Brownells and currently in production. They are mil-spec, and quality finished parts from this company, which has a great reputation.

It also includes a 6 position GI M4 carbine stock with adjustable pull and recoil absorption.

Here is what the customers had to say about the product:

Positives Recap for This Product

  • The complete lower kit comes with everything you need to finish the receiver plus grip, trigger, and stock
  • Good value for everything included
  • Easy to install, everything is mil-spec
  • Great directions and help from Brownells if needed

Negatives Recap for This Product

  • May come missing bolt catch springs, but Brownells quickly replaces them

Brownells – AR-15 Tactical Upper Assembly Build Kit

This affordable build kit by Brownells focuses on the upper assembly. This may be the perfect purchase for you if you’ve already gotten your lower and now you want the upper to finish off your build.

Though it focuses on the upper assembly (which is usually a simpler part), the parts that Brownells includes are good quality.

The Aero Precision upper receiver is made from 7075-T6 aluminum. This makes the part light and reliable.

To add to the reliability, the receiver uses M4-style cuts to ensure the smooth feeding. The M4 is the military version of the AR-15, so if it’s good enough for the military, it should be more than enough for you.

The upper receiver is stripped as well. This means that it’s finished and ready to install with compatible parts.

Speaking of compatible parts, Brownells chose all of these at mil-spec, so they fit easily with all other mil-spec parts and lower receivers.

This kit also comes with a DPMS forward assist assembly and ejection port assembly.

The upper assembly parts are all finished in a black finish for a tactical look and extra corrosion protection.

The upper assembly kit is made for the standard caliber, .223 Remington (5.56 NATO).

Here is what user reported about their experience with this upper assembly kit:

Positives Recap for This Product

  • Kit includes all the upper receiver and accessory parts you need
  • Affordable price
  • Finish has a nice look and quality protection
  • Upper receiver is good quality and consistent
  • Easy to assemble and install with other mil-spec parts

Negatives Recap for This Product

  • DPMS ejection port and forward assist are good but nothing special

Related: How To Hold an AR-15 

What Is A Build Kit?

There are different types of AR-15 build kits, but they all share the same common purpose.

Their job is boiled down to helping you finish the receivers on an AR-15.

In some cases, this means that they provide all parts and tools needed to finish the lower or upper receiver (or both).

In other cases, the build kits provide the tools needed to finish and install the parts you purchased separately.

Either way, it still falls into the category of a kit that helps you construct the receiver parts.

Sometimes, these kits can include other parts of the AR-15, but it doesn’t have to.

The focus on the receivers is because the receivers are technically the firearm. It’s the part that contains the firing mechanism of the rifle.

It’s also the part that’s more regulated by the government.

Why Build Your Own AR-15 Or AR-15 Parts?

There are several reasons you may want to consider building your AR-15 or AR-15 parts. These reasons range from personal to practical, but all are valid reasons.

Custom built AR-15 are a controversial subject, so it’s a good idea to be able to defend your decision in a reasonable way to those who don’t understand.

Who knows? You may be able to change some minds on the topic.

Here are just a few reasons you may want to build your AR-15 with a build kit:

You like to build things – Some people, like my father-in-law, love to take stuff apart and put it together again. 

He has built a couple of AR-15s at this point just because he loves to work with his hands and feel that sense of accomplishment when he puts together a complicated product.

This is a completely valid and easily understood feeling. If you give it a try, don’t be surprised at the immense amount of pride you feel when you fire an AR you’ve made with your own hands.

You want to customize your rifle – The AR-15 is considered America’s most popular sporting rifle, and one of the biggest reasons why is its huge level of customization.

There are thousands of options out there to help you get your AR setup exactly how you want.

Whether it’s a hunting build or competitive shooting build, using a build kit is key in getting the AR-15 just the way you want it.

You want to understand firearms better – The root of firearm safety and skill is knowledge.

Nothing helps you understand something better than putting all of an object’s little parts together into the whole.

Some folks want a grasp of how all the rifle parts work together for their understanding. If this is you, then doing an AR build with a build kit is essential for you.

You get an AR-15 for cheaper – If you have the patience, building your own AR can make a high-quality rifle much cheaper than buying it outright.

First, when you buy parts separately, they tend to be a little cheaper than when it comes pre-attached. This is because you don’t have to factor in the cost of labor.

Second, if you wait to buy each part until it’s on sale, you can get it for even less.

It may take a while, but the more patient you are, the more you save.

Related: How Far Can An AR-15 Shoot Accurately?

Features Of AR-15 Build Kits

Whatever reason you’re building your AR-15 for, you may want a build kit to help you out. But there is such a huge variety in the build kits, and you need a guide.

This section gives you a good start on what features to look for in an Ar-15 build kit. Keep this information in mind as you read the reviews later on.

Level Of Build Kit

This is the most important thing to decide before you start shopping for your AR-15 build kit.

What are you looking for it to do?

There are different levels of kits.

Some provide upper and lower receivers, buttstock, trigger assemblies, barrels, and more.

Others only come with the tools to finish an 80% receiver you purchased elsewhere.

In general, if you want to customize your rifle heavily, go with a kit that comes with the tools only. This way, you can buy the exact parts you want elsewhere.

If you want the experience of building the AR and you’re not as worried about the level of customization, then buy a kit with parts included.

This way, you also guarantee that everything fits without as much work.

Related: Best AR-15 Lowers 

Stripped Or 80% Finished.

If you buy a kit that comes with receivers (which most do), pay attention to the level of finish on the part.

A stripped receiver is finished. It has a serial number and is ready to install with help from the tools in the kit.

An 80% receiver is not finished, and it often doesn’t have a serial number, nor does it need one (see the answer in the commonly asked questions section).

It requires some extra work, but they’re a little cheaper. There are often great directions and guides included to finish the milling and drilling, so it shouldn’t be too hard.

Upper Receivers

The upper receiver is the chamber where the round is fired and ejected. Sometimes the upper receiver also comes with the barrel.

Upper’s can be made from lighter materials and must fit smoothly yet securely to the barrel and lower receiver.

The stock (not included in build kits) secure around the receiver.

Lower Receivers

The lower receiver is where the firing pin strikes the round and fires the bullet.

These parts are key to consistent usage of the AR-15. Look for a durable material with a good finish, and check out the user recaps for how it functions.

Sometimes these come with the trigger assembly, and the buttstock included.

The lower receiver connects to the upper receiver, trigger, and buttstock or stock.


Barrels are sometimes included in complete build kits.

If you’re comparing barrels, look for one that’s made from durable material and has some heat dispersing features such as specialized contour and free floating.


The buttstocks are also sometimes included with build kits. A well-designed buttstock can help absorb the recoil and keep your aim on the target.

Look for a buttstock that’s adjustable to your body and made out of a durable material with a good finish.

Easy Use

There are build kits out there that offer good tools, but they don’t include instructions on how to use them correctly.

There are also kits that give tools that do the job, but they aren’t as intuitive to use.

When you buy a build kit, be honest about your level of expertise in working on firearms.

If you’re new or not-as-skilled, get one that is proven to be easy to use.

The best way to see how easy a product is to use is to read customer reviews on the product.

We did that for you in the recaps section of each review. We make sure to point out any problems (or great successes) in this area for each build kit.


As always when shopping, make sure you buy something within your budget.

Build kits can get pricey depending on what’s included, so make sure to know what you’re willing to spend. However, don’t just go for the cheapest option if you need more parts or extra help.

If you are doing your build to try and save money, you need to check the prices of each of the products by clicking the link.

We make sure to mention the general price range of each option when compared to its other parts, but these items go on sale often.

An expensive item may not be that way when you click.

If you’re seriously into building AR-15s, bookmark this article and check back regularly to see if the prices have fluctuated.


Is the AR-15 an assault rifle?

No, the standard AR-15 you would buy for civilian use is not an assault rifle.

Many people mistakenly believe the “AR” stands for assault rifle when, in fact, it stands for ArmaLite Rifle (the company that designed it).

In the 1960s when the AR-15 was originally designed, it was an assault rifle capable of semi and full auto firing modes.

Then it was redesigned into the M$ for use in the US military. Later, it was rereleased to the public as the AR-15, but only with the semi-automatic function.

Without the full auto configuration, it is not considered an assault rifle.

Is it legal to build a fully auto AR-15 using kits?

No, fully automatic weapons are subject to regulation and restriction under the National Firearms Act of 1934.

This doesn’t mean you can’t own a fully auto weapon, but you must register and follow federal and state laws to do so.

However, building one is not allowed without a lot of paperwork, and the penalties are extremely stiff.

Make sure you know and follow federal, state, and local laws regarding firearms and help protect the reputation and the rights of responsible gun owners.

Do I need to put a serial number on my 80% finished kit?

Short answer, no.

As long as they’re 80% parts and you’re not building your rifle in a configuration regulated by federal and state laws, you can build without putting a serial number on it.

Here are some (but not all) controlled guns that you cannot build:

  • Short barreled shotguns
  • Short barreled rifles
  • Machine guns (full auto)
  • Destructive devices

You must also build the gun for personal use, not for resale or for gifting to someone else.

For a complete answer, check out our article on serial numbers and gun builds.


We hope you enjoyed our review of the best AR-15 build kits.

Taking the time and effort to customization an AR-15 to match your style is a great way to even more into the hobby of firearms.

These kits are a great way to help you finish the build or do one from the ground up.

It’s something of a rite of passage for gun enthusiasts to do their AR build and with these kits you can do so confidently.

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