We tested dozens of AR-15 Lower Parts kits and found that Palmetto State Armory and CMC Triggers had the Best AR-15 Lower Parts Kits.
I used to think that just any old lower parts kit would do and that they were all the same. After building dozens of my own AR-15s, I found that there are differences worth paying attention to.
In this guide you will find our favorites along with details of what we have experienced over many years. We will list our tips on what to look for that are especially important for the first time you build your own AR-15.
Keep reading to save money, time, and a lot of confusion.
Quick Summary of Our Favorites
Best AR-15 Lower Parts Kit
Palmetto State Armory Classic Lower Parts Kit – Best Overall
- MSRP: $25
- Includes:
- Magazine catch assembly
- Bolt catch assembly
- Trigger guard assembly
- Front pivot pin assembly
- Rear takedown pin assembly
- Safety selector assembly
- Buffer tube detent/spring
- Standard AR-15 Grip
- No FCG
I have used 5 or 6 different Palmetto State Armory lower parts kits over the past 10 years.
They have every possible combination of kit I could ever want. They have just a basic lower parts kit like linked above, but they also have kits that include different popular grips. (See our Best AR-15 Grip Guide for our favorites!)
My favorite is the full lower build kit that includes the lower parts kit plus a grip, stock, FCG, and buffer tube assembly. They have options from Magpul, B5, BCM, and MPT to choose from. In most cases I find this is the best value.
I like how their kits have each assembly separated into separate bags. This makes building my lower easier since I can just open the bag for the assembly I want to work on. I don’t have to worry about getting anything mixed up, and if I need to stop part of the way through, it is no issue.
The lower build kits also include an extra takedown spring and detent. This is a nice extra since these are the most common parts that I lose when assembling my lower. It never fails that I launch a spring across the room to never be found again.
The part quality is usually top notch, however, on my last build I did have a takedown pin that had a rough finish along with the safety selector. I was able to clean it up somewhat, but it was still a disappointment.
CMC Triggers AR-15 Lower Parts Kit – Best Finish
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- MSRP: $35
- Includes:
- Magazine catch assembly
- Bolt catch assembly
- Trigger guard assembly
- Front pivot pin assembly
- Rear takedown pin assembly
- Safety selector assembly
- Buffer tube detent/spring
- No FCG
The CMC Triggers lower parts kit is a great option when you want to use a non-mil-spec trigger.
This kit is made in Texas and I find that the finish and quality are top notch. They make the controls on my rifle super smooth without any break-in time needed.
This kit is a great value as well. I often find these on sale at Primary Arms for less than $20! When the price drops, I always buy a few.
The only thing I don’t like about this kit is the packaging. The metal parts are in one bag, the springs in another, and the detents in another. I would prefer them to be separated by assembly. It takes a little time to sort everything out, but the quality and price make up for it, I think.
BattleHawk Armory AR-15 Lower Parts Kit – Best Value
- MSRP: $30
- Includes:
- Magazine catch assembly
- Bolt catch assembly
- NO Trigger guard assembly
- Front pivot pin assembly
- Rear takedown pin assembly
- Safety selector assembly
- Buffer tube detent/spring
- Trigger Pins
- Trigger Springs (mil-spec)
- No full FCG
I found this kit included with a KAK lower that was on sale, so I gave it a shot. The lower was cheaper than normal, so this kit was essentially free compared to normal prices.
I was impressed with the finish and the quality of all the parts. Everything went together smoothly and the controls on my build were very smooth.
I like that this kit comes with trigger pins. This means I can buy any standard or drop-in trigger and not have to worry if it comes with trigger pins or not.
It also comes with mil-spec trigger springs. This is a little strange to me, and I am not sure why. But, at least it gives me backup springs for the future.
This kit does not come with a trigger guard. This is great when I am using a lower with one built-in, but not so good when I am using a mil-spec lower.
I don’t like how this kit was packaged. It was all just in one bag. Not a big deal after a few builds, but not great for your first one.
Aero Precision Lower Parts Kit – Best for Aero Lowers
Save 5% off at Optics Planet with code “survivalstoic”
- MSRP: $36
- Includes:
- Magazine catch assembly
- Bolt catch assembly
- NO Trigger guard assembly
- Front pivot pin assembly
- Rear takedown pin assembly
- Safety selector assembly
- Buffer tube detent/spring
- No FCG
- 4-40 set screw for Aero Lowers
Aero Precision makes some of my favorite AR-15 stripped lowers. This lower parts kit is the perfect match for their lowers.
One of the things I like about Aero Precision lowers is the threaded rear takedown pin spring hole. It is tapped for a 4-40 set screw. This kit comes with the screw that I need, while the lower does not come with one.
So, if you want to take full advantage of the threaded hole, it is easier to just get this kit.
The price is similar to other lower parts kits. Just keep in mind this kit does not come with a trigger guard.
I found that the parts were in a couple bags, but not really organized in any particular way. One of the bags had a staple in the top, which was unusually aggravating for some reason.
The parts had a lot of rust preventive on them, and it was hard to get off. The finish on them was OK, but they did not look as good as some of the other kits I have used.
Overall this kit works great in my lowers, but I was disappointed in the looks of the last kit I used.
Rise Armament Lower Parts Kit – Best Packaging
- MSRP: $45
- Includes:
- Magazine catch assembly
- Bolt catch assembly
- NO Trigger guard assembly
- Front pivot pin assembly
- Rear takedown pin assembly
- Safety selector assembly
- Buffer tube detent/spring
- Trigger Pins
- No FCG
There are a couple things that I like about the Rise Armament lower parts kit.
All the parts are packaged into a nice blister pack. I was able to open it without dropping the parts everywhere, and it made a nice little tray where I could see everything and pick out what I needed. Much better than everything just thrown into a bag.
I also like that this kit comes with two trigger pins. I can choose any trigger that I want and not have to worry if it comes with trigger pins or not.
This kit does not include a trigger guard, so it is perfect for a lower with a built-in trigger guard like an Aero Precision M4E1 or a Spike’s Tactical stripped lower.
The only thing I don’t like about this kit is the finish on the parts. You can see how the mag release and the channels in the takedown pins are a little rough.
The price for this kit is a little higher than the others, so it is hard to recommend unless it is on sale.
How We Tested the Best AR-15 Lower Parts Kits
Over the past 10 years I have built various AR-15s and tested them at the range and in competitions. I looked at overall finish quality, smoothness of operation, dimensional specs, availability, price/value, packaging, and overall ease of using them in my build.
I then tried them with various lowers, both Mil-spec and higher end Mil-spec + lowers. I have fired at least 250 rounds through each, with my top picks seeing well over 1,500 rounds over the years.
Our top picks included input not only from our team, but the input from many others in our community, both in person and online. We considered everyone’s experience and opinions over the past 10 years to achieve what we think is the most balanced and comprehensive review available.
Tips for Choosing the Best AR-15 Lower Parts Kit
While it may seem that any lower parts kit will do, there are a few things to watch out for. Below are our tips for choosing the best QR-15 Lower Parts Kit based on our experience and testing.
Quality
Quality is obvious, no one wants to buy junk. But it is not easy to know before you buy.
One way to be sure is to buy from a reputable manufacturer. If the price looks too good to be true and it is made by a company that has a strange name, it may not be the best quality.
I find that companies who make other AR-15 components and have been in business for at least a few years usually have the best quality.
Most companies don’t make the lower parts kit items themselves, they contract it out to third party machine shops. Some parts kits from different companies may have actually been made in the same place without you realizing it.
So, you may really like a certain brand, but often it doesn’t make sense to pay the extra price.
Finish
While the materials used and the dimensional accuracy of the parts are important, I find that most companies get this right. Where they tend to slip up is in the finish quality of the parts, both surface finish and treatment.
The metal parts in a lower parts kit usually have a black phosphate coating to protect them from corrosion. I find this coating, along with the surface finish of the machined surfaces, dictates how smooth they feel once they are assembled into my rifle.
For example, the takedown pins will be very hard to slide open and closed if the finish inside the detent channel is not smooth. Similarly, the safety selector will be hard to switch on and off if the outside finish and the detent channel are not smooth.
Lower Parts Kit Contents
I also find that not all lower parts kits contain the same parts. You would think it would be standard, but it is not. Some may or may not include a trigger (fire control group of FCG), trigger guard, spare springs or detents, or other parts to build an AR-15 lower like grips, buffer tubes, and stocks.
I like to determine everything I want on my AR-15 before I build it, so I am not buying extras or missing something.
Here are the parts that come in most lower parts kits:
- Magazine catch, Spring, and Button
- Bolt catch, plunger, spring, and roll pin
- Front Pivot pin, detent, and spring
- Rear Takedown pin, detent, and spring
- Safety selector, detent and spring
- Buffer retainer and spring
Some kits may include:
- Trigger guard assembly
- Fire Control Group (trigger assembly)
- Trigger Pins
- Grip
Note on Trigger Guards:
If the lower I plan to use is a mil-spec lower without a built-in trigger guard, then I make sure my lower parts kit comes with one. I have also purchased one separately, although it is usually cheaper to just buy a kit with one.
If my lower has a built-in trigger guard, then I don’t need a separate one in the kit.
Note on FCGs:
I usually like to use a non-mil-spec trigger. I think it is one of the most noticeable upgrades that can be done to an AR-15. Many lower parts kits can be purchased without a trigger or FCG. Then I can just buy the trigger I want separately, and it saves me money.
However, some triggers do not come with trigger pins and some lower parts kits do not either. So, I find it is important to check. This happened to me once but luckily, I had some in another kit.
Organization
On my first few builds, a big pile of parts was intimidating. There are a bunch of springs and detents, and I had no idea where they went.
I find that if my lower parts kit has the parts separated, it makes it much easier. I especially like the ones that put each part group together.
For example, separate bags for the mag release parts, bolt catch parts, takedown pins, and so on. As I move through each stage of the build, I just open the next bag and don’t have to worry about getting anything mixed up.
Our top pick, the Palmetto State Armory Lower Parts Kit, has the parts in separate bags organized this way.
Stay Updated and Learn More
After you choose the best AR15 lower parts kit for you, be sure to stay up to date on all of our content by joining our Newsletter. Each week, we include tips on how to stay mentally prepared with actionable ideas and strategies. We also include any good deals we have found, plus updates to our content.
We would like to thank AmmunitionToGo.com for providing the ammo that we used to test these AR-15 lower parts kits at the range. We used Fiocchi M193 5.56 ammo for most of our testing since it is a standard NATO round.
Now, check out our other Self-Defense guides for more from AR-15 Basics to our favorite parts and upgrades. Also be sure to check out our favorite AR-15 stripped lowers, the Best AR-15 Stocks, the Best AR-15 Triggers, and the Best AR-15 Charging Handles for your next build!
Also check out our review of TacPack, a cool tactical gear subscription box that includes a lot of different AR-15 parts each month!
