Top AR-15 Build Kits For Your Next Project: From Basics to Ballistics

1. Best Complete Build Kit: PSA

Pros

• Lots of options
• Great inventory
• Solid price point

Cons

• Non-ambi controls
• So-so trigger

Palmetto State Armory at any given time has a dozen or more AR-15 kits up for grabs in pistol and rifle format. One of the best bangs for the buck is their Lightweight M-LOK kit which includes a nitride treated 15-inch 4150V chrome-moly steel barrel, chambered in 5.56 NATO, with a 1:7 twist, M4 barrel extension, and a carbine-length gas system.

As it includes PSA’s Classic Freedom Lower Build Kit along with a full-auto profile BCG with a 9310 bolt, all you need is a lower and the time to build it up. In short, this is as close to an AR-15 in a box as you can get.

2. Best Builder Set: Aero Precision

Pros

• Solidly built
• Includes all major components

Cons

• No LPK
• No Barrel

A household name in the AR receiver game, Aero Precision can set the home builder up with both an assembled upper — with forward assist and dust cover installed — and a stripped lower combo set that won’t break the bank.

We recommend their M4E1 Builder Set which just needs a BCG, barrel, and LPKto finish out.

It comes standard with a nylon-tipped tensioning set screw in the grip tang of the lower to aid in fitment between the receivers and M4 feed ramps.

3. Best Lower Parts Kit: Brownells

Pros

• Always in stock
• Made in the USA
• Mil-spec, easy installation
• Brownells Quality

Cons

• Rapid fire trigger suffers at distance performance

Bravo Company has dozens of upper receiver groups running from short 9- and 10.5-inch pistol uppers to 20-inch rifle models in a variety of calibers.

About the most-feature rich of these is their Kyle Defoor KD4 series uppers with SS410 barrels, ideal for use with 77-grain pills.

4. Best Custom Kit: Timber Creek

Pros

• Ambi safety
• Loads of colors
• Fantastic charging handle
• No FFL required

Cons

• Expensive
• No Lower
• No Upper or Barrel

Timer Creek Outdoors is one of the fastest-growing black rifle accessory makers in the country, and for good reason– they are good at what they do and make a quality product that performs with lots of custom options.

Their build kits include touches that take the performance of most rifles to the next level — including an oversize charging handle, extended mag release, and quality M-Lok handguard — often in colors designed to really make your rifle your own.

5. Best Trigger: CMC

Pros

• Fantastic trigger
• Simple installation
• CMC quality
• Looks great

Cons

• 3lb pull weight can hamper distance shooting

Texas-based CMC is primarily known for their excellent drop-in trigger packs; however, they also pair their 3.5-pound single-stage flat and curved triggers with a complete lower receiver parts kit. This pairs well with the company’s enhanced buffer set.

6. Best Small Parts Kit: Geissele

Pros

• Superior trigger
• Straightforward installation

Cons

• Easy to lose parts
• Expensive
• Often backordered

Pennsylvania-based Geissele is well-known in the AR-15 market even if they have gained something of a reputation of being a bit on the expensive side.

The good news is that their Super Duty and Ultra Duty lower parts kits are affordable and offer a great value. Add one of their buffer tube setson a stripped lower plus a grip and mag and you are ready to finish it out with the upper of your choice.

7. AR Trigger Runner-up: Geissele SRF- Brownells

Pros

• Great value
• Always available

Cons

• Fitting may be required
• Mag catch can have fit problems
• QC issues

For roughly the cost of one of Geissele’s SD or UD kits, Brownells offers a lower parts kit paired with one of Geissele’s glass-smooth and fast-shooting Rapid-Fire Triggers, which can be tuned in either 3.2- or 4-pounds by swapping out the included trigger springs.

While the Rapid-Fire Trigger pulls like a single-stage, it resets like a two-stage, making it ideal for many better builds.

8. Best Two-Stage Trigger Kit: Geissele + Brownells

Pros

• Top notch trigger
• Simple installation

Cons

• Some pieces may need to be deburred

Suppliers of high-end precision-driven AR platforms to the British military and others, LMT Defense offers both a complete lower parts kit that includes their two-stage trigger group and what they bill as their “Light” kit that comes sans trigger group to allow builders to make that personal decision themselves while still having LMT internals in their lower.

In short, unlike a complete rifle or pistol, AR-15 build kits are more on the component side of things, with varying degrees of “some assembly required” to finish the gun into a range-ready firearm.

These range from joining up a complete lower to a complete upper and adding a magazine and lube– possibly the easiest level– to building an AR from the ground up. Then, of course, there is everything in between.

Of Uppers and Lowers

For those who skipped AR-15 101, the platform is comprised of not one receiver as on most firearms, but two: an upper and lower.

Only one of these, the lower, is serialized and therefore considered a controlled item by ATF. Each can be purchased “stripped,” which requires further building out, or complete, which only requires final match up to be ready to roll.

Keep in mind there will typically be some minor “play” between uppers and lowers, especially if you select them from two different manufacturers, a factor that can be alleviated by picking up a set of matched lowers which have been machined to tight corresponding tolerances to eliminate the “slop.”

Upper receivers can be challenging. By far, a barreled upper is an easier learning curve to work with, especially for those who are on their first build and allow the builder to avoid having to pick up a torque wrench and reaction rod.

Also, with the barrel already installed right out of the box by a reputable firm, it alleviates the worrisome question of having the correct headspace in the chamber. While starting with a stripped upper is more of a heavy lift for inexperienced builders, it does allow much more customization when it comes to barrel choice.

When it comes to lowers, forged 7075/76 aluminum lowers advertised as “mil-spec” should be the baseline for a build, while a lower parts kit, buffer tube, and stock/brace are not an overly complex task to install correctly. There are any number of helpful (free) videos out there to walk you through it — and we have a complete visual guide on assembling an AR if you’re so inclined.

As a tip, threaded trigger guards are great as they keep you from having to drive a roll pin through that somewhat easy-to-break ear with a hammer. Likewise, when you install the buffer tube and receiver extension, be sure to apply a serious stake to the castle nut to avoid having it unwind with vibration while in use, which is a bummer.

The fun of getting greasy

For many in the gun community, there’s more to the sport of shooting than simply buying a gun off the shelf and using it.

Some folks love tinkering with firearms as much, if not more, than actually shooting them. Especially these days, a lot of us grew up playing with GI Joes, and later on, spending hours customizing digital firearms for our favorite annually-released first-person shooters. Well, you can do that customization in real life, too, and one of the best ways to do it is to build an AR15 with a build kit.

Saving a buck (or $50)

Second, as the market for new and used ARs is more expensive than it has been in a long time, people are looking for ways to obtain high-quality parts at a good value.

One approach is to reduce labor costs by assembling the rifle yourself.  Doing so not only saves you the money of paying someone to build it on a factory line, but you’ll also get the choose the parts that you want, exactly, and also you’ll pick up new skills.

Getting the parts in a kit makes the process a little more streamlined overall.

Parts Kits

One of the more common and often cheaper types of kit are the ones meant to populate a bare lower receiver.

These typically come with everything you need for a trigger, magazine catch, and bolt release, in addition to the retention pins. These simple kits are excellent for someone who has an upper ready-to-go and wants the experience of building a lower with the necessary parts or upgrading something particular about their AR.

Partial Build Kits

Second, you’ll find kits that include all of what we’d just mentioned, plus some furniture, usually the upper handguard, and you’ll sometimes find a stock included as well.

These kits are great for folks who either want to change the look and performance of an existing rifle or have a bare lower receiver and a barreled upper receiver lying around that they’d like to turn into a fully functional firearm. These kits can often be an incredible value for the money.

Complete Build Kits

You’ll find the most expensive kits have everything but the lower receiver. That is to say, they have a complete lower parts kit, some furniture, and an entire upper receiver, including the barrel, bolt carrier group, muzzle device, handguard, and maybe even some iron sights. If the upper is assembled, which it probably will be, the price on these starts to climb a little bit, but you still save on the labor of building the lower.

Luckily, these can be shipped directly to your house, thanks to the absence of a serialized lower receiver.

Trigger Kits. Finally, some kits focus on the trigger, often containing just the trigger itself and any relevant springs. These kits often feature some of the best triggers available and cater to individuals with a fully functional rifle who wish to upgrade the trigger.

Using one of these kits is a fantastic way to enhance a basic AR — tailoring its performance to your preference, especially since many individuals aren’t fond of the mil-spec triggers common in most ARs today.

These days, many AR owners typically begin their pursuit of the ArmaLite-style rifle by acquiring one or two complete guns then balancing out their collection with at least one or two personally assembled guns from kits and taking it from there in either direction.

The primary reason for opting for a kit build is that the builder can research and select each part meticulously, optimizing the build for a specific purpose (more on this later).

The result can range from the beautiful to the comical, and span from low-tier budget to super Gucci custom– all with the easy tweak of a handful of parts and components.

Few constructions in the consumer marketplace offer such variety. Additionally, the build process instills the builder with a skillset and knowledge base that takes them far beyond the basic understanding of manipulation or nomenclature and allows them to supervise as much of the production of their gun as they want.

They are responsible for the staking of parts. They are the one who installs every pin and spring in the lower. This makes the satisfaction of producing a working firearm both a personal and fulfilling experience: a journey into ballistic self-improvement, if you will.

1. Purpose-driven

The correct first step in any build is to define a list of expectations for the result once the final lube is added and the gun is function checked. Plan out your build in a road map of sorts by making a build list from the raw receivers to the barrel, LPK, grip, handguard, BCG, muzzle devices, and so forth.

For example, if all I have is a lower, then I’ll need one of the kits that includes everything else. I appreciate the convenience of not having to create a spreadsheet and shop around.

If, on the other hand, all I need is a new trigger, then a more complete kit will leave us with a pile of spare parts, which will either sit in a drawer or inspire us to further empty our wallets on parts to turn our spare parts into another AR.

What kind of optics or sights will you be using? This will point to whether you want an A2, A3, or A4 upper and what kind of top or quad rail system it uses.

Are length and weight a factor? This outlines how long a barrel is and the type of stock used.

2. Overall Value

Second, I think about the overall value involved in a given kit. Triggers are generally sold with a minimum of parts, so those are going to be as cheap as they can get. If, on the other hand, you can find a handguard or stock that you like on a good sale, you might be able to score it cheaper than buying it in a kit and then getting a smaller kit.

It’s always worth looking at a few different options if budget is a major issue for you in building an AR.

2. Component Quality

Third, quality matters. Since we’re saving money by buying a kit, it’s typically a sound investment to buy the best parts that you can.

This is especially true in parts that will get a lot of wear and tear, such as the trigger and magazine release. The last thing you need, especially in a rifle you might use in self-defense, is for the magazine retention spring to break, leaving you with a bullet in the chamber and nothing but a club with which to defend yourself.

4. Barrel Considerations

Do you intend to suppress it? This tells you if you want a threaded muzzle or want to use a QD attachment for the can of your choice.

Will you take it hunting where allowed– check your caliber choice with this– and if so, what kind of load will you use? This can lead to barrel length and twist decisions. If you’re looking for distance performance a 18-inch or longer Valk or Grendel upper might be appropriate, — but if you’re trying to keep your home safe or want a more truck-friendly build something like a .300 Blackout or traditional 5.56 upper would be a better option.

5. BCG

What is the purpose, for instance, will the gun be used sparingly as a range toy or will you stake your life on it in a potentially extended self-defense scenario? This will help you choose the appropriate BCG.

6. Aesthetics

Lastly, kits are a great way to have some say in the aesthetics of your AR. Some triggers, for instance, come in a variety of colors and can be a terrific way to add a pop of color to your rifle without getting a receiver that’s been coated in some wild new finish.

Additionally, the kits that come with furniture allow you to pick the final look of your gun while you’re in the planning process of a build. All in all, these kits are a way to customize an AR precisely to your liking.

Take everything you know about buying anything and throw it out the window when it comes to shopping for gun stuff, especially online.

Failing to research

While you can head to eBay or Amazon for just about any household goods you can name, prejudicial banking practices and deplatforming have driven many firearm industry vendors to more niche sites.

Further, shipping times are often longer and controlled items like finished lowers have to be transferred through federally licensed firearms dealers, adding extra steps to the process.

With that being said, don’t get in a rush. Do your research!

Skimping on the most important bits

Don’t compromise on the essential components of the AR – the barrel and the bolt carrier group – by opting for flawed, inexpensive options.

This is where most of the wear and tear on an AR platform will occur because this is where the force of the cartridge’s ignition takes place and the action is cycled, with metal-on-metal contact.

As such, this is where catastrophic failures will most often occur. At a bare minimum, make sure the BCG is of good quality, from a reputable maker, and is Magnetic Particle Inspected (MPI)– sometimes just seen as Magnetic Tested (MT)– high pressure tested (HPT) and shot-peened (SP).

If you are on a tight budget, feel free to try to nickel and dime almost anywhere but the barrel and BCG, or save for a couple more weeks for something better.

Lack of tools

Once you get your components, make sure you have the proper tools to complete an AR build.

Barrels will need to be installed and torqued down correctly, gas keys and castle nuts have to be staked, roll pins will require properly sized punches.

Investing in tools like a bench block, a small table vice, an AR-15 armorer wrench/multi-tool, hammers (preferably nylon and brass), the right-sized punch set, anti-seize compound/grease, clevis pins, and go/no-go gauges might seem overwhelming initially.

However, these tools will prove cost-effective if you undertake multiple builds over the years. Gunsmithing tools do not have an expiration date.

Check with your local gun store as, if they have a smith on staff, they often run build classes for a nominal fee if you bring your parts and will help with tips, tricks, and the loan of some of the more rarely used tools. Expect to do all your own work, however. Speaking of which…

Keeping it legal

Given the plethora of AR components available, it’s easy to make a mistake and inadvertently violate the National Firearms Act (NFA), potentially resulting in a decade-long sentence in federal prison.

Fundamentally, when it comes to lowers, if it is sold specifically as a rifle lower, it needs to stay a rifle lower for its entire existence.

The same goes for pistol lowers. When matching the two receivers up, keep those NFA regs in mind to ensure you stay away from having an illegal AOW or SBR unless you have an approved Form 1 beforehand.

Going even further, accessories can run afoul of the law as well, for instance attaching a vertical foregrip or an M4 stock to an AR pistol. Also, when counting a muzzle device into the minimum overall barrel length of a rifle, be sure that the device is permanently attached– just adding some red Loctite doesn’t count.

When in doubt, check it out before you build it. The last thing you want to do is go to some public shooting range somewhere where a photo of you and your questionable kit makes it into circulation.

Also, remember you have not only federal law but in many areas state laws that may affect your build. Finally, be sure you are building for your personal use, rather than to sell the finished product specifically for a profit– which can bring unwanted scrutiny from the alphabet guys.

In short, be well-informed about what you are purchasing and assembling.

• $50-$100. For about $50, it’s possible to find a reasonably basic lower parts kit that has everything you need to populate the lower, though for that price, don’t expect the world in terms of parts quality. I sometimes recommend these to folks who are building a budget rifle or want some spare parts.
• $100-$200. For about $150, you can get into more complete kits that may well include some furniture, and the sky is more or less the limit as far as what you get in terms of the trigger, handguard, and stock.
• $300 and Above. Over $300, and now you’re talking about the best triggers on the market, including binary triggers that can dramatically affect the rate of fire. The best match-grade triggers will also fall in this price range.

For kits, the pricing largely depends on the quality and the number of parts included.

It’s not apples to apples to compare a simple lower parts kit to something that has everything you need to build a gun. There are a variety of options in all of the different types of uppers to meet the needs of folks’ different budgets and firearm needs.

1. YouTube, LPK Installation Videos
2. Stag Arms Blog, The difference between Gas Piston and Direct Impingement technology for an AR-15
3. ATF, ATF Form 1, Application to Make and Register a Firearm
4. Gun Trust Guru, Can I Add a Vertical Fore Grip to My AR-15 Pistol?, July 10, 2019
5. ATF, If a person has a pistol and an attachable shoulder stock, does this constitute possession of an NFA firearm?
6. ATF, Definitions of a Firearm
7. ATF, What does “any other weapon” mean?
8. ATF, ATF – National Firearms Act Handbook