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- Alfred Mendoza
- March 25, 2024
Building an AR-15 allows you to completely customize every part of your gun to exactly fit what you want from your rifle. However, choosing the lower parts kit is also one of your most complicated parts of your build, as it may affect your finished product’s quality and reliability. To help you find the best AR-15 lower parts kit, our team of experts tested out ten lower kits for you to choose from.
To know more about the features of these highly customizable kits, keep on reading.
- Meets or exceeds military specifications
- Color-coded for easy assembly
- Very smooth pull and a clean break
- Fit is perfect on many guns.
- Takedown pin detents are oversized.
- Includes Magpul MOE Grip
- Has Magpul Billet Trigger Guard
- The components are corrosion-resistant.
- Cost-effective and high-quality.
- This kit is made in the USA.
- All pins were sized perfectly.
- Give the ability to choose what component to put.
- Offers trigger-free parts kit
- High-quality
- It lets you save money by not spending with components that you don’t need.
Table of Contents
Top 10 Lower Parts Kits for AR-15
1. CMMG - AR-15 Lower Parts Kit
The CMMG – AR-15 kit is an AR-15 lower parts kit that contains every internal part needed to complete or rebuild an AR lower receiver. It features high-quality components designed to work with each other to ensure smooth operation and everything a shooter needs to complete a lower receiver build.
These components come in color-coded bags organized in related parts for easy assembly, excellent for beginners who had never built an AR-15 before. The CMMG also includes molded-polymer A2 pistol grips and a Mil-Spec trigger that offers a single-stage 6 to 6½ lbs service rifle pull.
PROS
- Meets or exceeds military specifications
- Color-coded for easy assembly
- Very smooth pull and a clean break
- Fit is perfect on many guns.
- Takedown pin detents are oversized.
CONS
- A2 pistol grips aren’t comfortable.
- Buttstock not included
2. Aero Precision - AR-15 Lower Parts Kit
The Aero Precision Enhanced Lower Parts Kit is a lower receivers kit with a Magpul MOE grip and billet trigger guard. Its components are manufactured in the United States of America and weigh 8.1 ounces altogether.
This Enhanced Lower Parts Kit comes with 28 different mil-spec components perfectly tailored to fit your AR. Each of the components of this Enhanced Lower Parts comes with corrosion-resistant coatings, giving you durability and smooth operation.
PROS
- Includes Magpul MOE Grip
- Has Magpul Billet Trigger Guard
- The components are corrosion-resistant.
- Cost-effective and high-quality.
- This kit is made in the USA.
CONS
- Some components require fitting.
3. CMC Triggers - AR-15 Lower Parts Kit
The Sharps Bros. unit is a budget AR rifle complete upper receiver that uses Mil-Spec Type III hard coat anodize billet with dust cover. This upper comes with a forward assist kit installed, a charging handle, and a bolt carrier group.
It is also constructed from 7075-T6 aluminum and features a “SHARPS BROS” discretely engraved on both sides. This complete upper receiver only weighs 9 oz and best used for .223, 5.56 NATO, .300blk, and 6.5 Grendel builds.
PROS
- All pins were sized perfectly.
- Give the ability to choose what component to put.
- Offers trigger-free parts kit
- High-quality
- It lets you save money by not spending with components that you don’t need.
CONS
- Do not have a pistol grip screw
- The trigger guard is plastic
4. Geissele Automatics LLC - AR-15 Lower Parts Kit
The Geissele Automatics LLC Kit contains top-quality steel for all the components necessary and high-end internal parts to get your lower part operational. This kit doesn’t come with the trigger and pistol grip that you may not want.
This kit also features lower receivers manufactured to “mil-spec” M16 / M4 dimensions ensuring optimum fit and function in your AR rifle or carbine. This kit also comes with a fire control system comprising hammer, trigger, disconnector, and pins, all “personal” parts of any custom AR-15.
PROS
- The kit uses high-quality steel for all the components
- It comes with the major AR lower components
- Crisp, easy-to-use safeties
- It fits a wide variety of mil-spec lowers
- Manufactured to “mil-spec” M16 / M4 dimensions
CONS
- The magazine release button may need hand fitting
- It does not include a grip
5. M&P AR-15 Complete Lower Parts Kit
The M&P AR-15 Rifle Complete Lower Parts Kit is an Enhanced Lower Parts Kit that includes everything you need to complete your lower receiver. All you have to do is find a stripped lower receiver and stock assembly of your choice. This kit is easy to install and also gives you the flexibility to add your own aftermarket upgrades.
The M&P AR-15 Rifle Complete Lower Parts Kit also features 20 total components built on par with military specifications. However, it doesn’t come with a lower receiver.
PROS
- Well organized LPK, quality materials
- Affordable price
- High-end OEM
- Excellent and durable finish
- Famous and respectable brand
CONS
- The safety selector is so rough and not ambidextrous.
- No trigger assembly
6. Double Star - AR-15 Lower Parts Kit
The DOUBLE STAR LOWER PARTS KIT is an AR-15 lower receivers kit that features high-quality American made parts and everything you need to complete your lower receiver. The kit includes a fire control group constructed from mil-spec heat treated 8620 steel, made to last for the weapon’s lifetime. It also comes with a smooth finish on all touchpoints and a crisp trigger pull with minimal creep or drag. Its lesser lower kits also use metal injected molded, making this kit an affordable choice.
Double Star also uses coiled steel spring pins instead of the standard split roll pins, so their parts are easier to install than the others. This kit has everything you need, including an additional takedown detent and spring as a back-up if one spring flies away during installation, never to be seen again.
PROS
- Oversized selector
- Smooth trigger
- Excellent reset
- Single-stage triggers
- Comes with extra detent and spring for the pivot pin.
CONS
- Difficult To Adjust
- Trigger guard is loose and has finish defects
What’s In A Lower Parts Kit?
- Pistol Grip
- Buffer Retainer and Spring
- Magazine Catch Assembly
- Safety Selector
- Safety Selector Detent
- Safety Selector Detent Spring
- Trigger
- Trigger Spring
- Trigger Pin
- Trigger Guard Assembly
- Hammer
- Hammer Spring
- Hammer Pin
- Disconnector
- Disconnector Spring
- 2 Takedown Detents and Springs
- Bolt Catch
- Bolt Catch Spring
- Bolt Catch Roll Pin
- Bolt Catch Plunger
- Rear Takedown Pin
- Pivot Pin
Things to Consider
Budget
When buying the best AR-15 lower parts kits, it is best to remember that the primary reason for buying a build kit or parts you need rather than separately purchasing them is to save money. Try to calculate each part’s actual cost when you buy them individually and compare the cost when you buy the best AR lower receiver kits on the market. Learn how you can build an AR-15 the cheapest way possible here.
Ergonomics
Ergonomics is also one thing that you must consider when buying an Enhanced Lower Parts Kit. It is best to focus on their materials or the quality control of the company. Determine whether the parts are mil-spec or premium build, as it may greatly affect your lower parts kit choice. Mil-spec kits come with simple and easy to build operation, while premium builds are mainly determined by personal preferences and are more expensive.
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Functionality
Most shooters are usually enticed with the overall “fit and finish” of the lower parts kit, which is an important consideration when assembling and disassembling the parts. The fit and finish of your lower parts kit also dictate your build’s functionality after installation. Hence, we recommend that you learn every part you slid into your build to make it function at its best potential. Many find AR-15 featureless grips beneficial when it comes to better functionality.
Durability
It would be best to consider your lower parts’ durability to ensure your build’s overall functionality and life span.
We suggest that you find the best lower parts kit like CMMG that offer precision-machined components made of top-quality steel with advanced finishing techniques, nickel boron, or Teflon.
Nickel-boron coatings were synthesized on mild steel by the electroless deposition method. [1] These types of coatings are corrosion-resistant.
Inclusions
Not all parts kits or build kits for AR-15 come with everything you need to build your lower parts. So, having many inclusions are helpful for your decision-making. We recommend that you find the best lower parts kit that includes a Fire Control Group, AR-15 stock and buffer system, pistol grip and trigger that could make your build better. You may also install a free float quad rail and add a foregrip bipod for more functionality.
FAQs
AR-15 lower parts kits aren’t the same. Some kits are mil-spec and premium built, and there are a few instances that the parts’ sizes differ from one another. Some kits provide roll pins for the trigger guards that are oversized for AR rifles. These instances usually happen because of the type of coatings and materials used for each part.
No, the AR-10 and AR-15 lower parts aren’t the same and are not interchangeable. Although most AR-15 LPKs will work with the AR-10, this isn’t the case for AR-10 lower receivers. The AR-10 shoots larger calibers, so its receiver and magazines are larger than AR-15.
Based on reliable reviews, buying quality lower parts kit matters because quality usually equals durability and functionality. Companies tend to price their kits higher when their quality control is higher and better, too.
And Our #1 AR 15 Lower Parts Kit is...
Based on extensive research, the CMMG is our #1 AR-15 lower parts kit because it features high-quality and mil-spec components designed to ensure smooth operation. This kit also comes in color-coded bags to organize related parts and for easier assembly.
It also includes a molded-polymer A2 pistol grip and trigger with a single-stage 6 to 6½ lbs service rifle pull. This lower parts kit is also best for the first time lower receivers builders.
Our #1 Recommendation
CMMG – AR-15 LOWER PARTS KIT
- Color-coded for easy assembly
- Very smooth pull and a clean break
- Versatile
- The trigger doesn’t creep for mil-spec
