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Best AR-15 Lower Parts Kits [2021]

Are you currently looking for a new lower parts kit for your AR-15? If so, you’ve arrived at the right place and your search is about to come to an end.

Best Overall: Palmetto State Armory Magpul MOE Lower Build Kit

Palmetto State Armory Magpul MOE Lower Build Kit

The Palmetto State Armory Magpul MOE Lower Build Kit is an overall solid option for a lower build kit thanks to its use of sturdy Magpul parts and mil-spec design.

See on Palmetto State Armory

Best Budget Pick: CMMG AR-15 Lower Gunbuilder’s Lower Parts Kit

CMMG AR-15 Lower Gunbuilder’s Lower Parts Kit

The CMMG AR-15 Lower Gunbuilder’s Lower Parts Kit is a solid choice for a budget lower parts kit that comes with the basic essential items. While it lacks a grip, trigger, or a trigger guard, it comes with all of the other items that you will need. If anything, investing in this kit could be a good idea if you want to have spare lower parts on hand to serve as future replacements for damaged components.

See on Brownells

Best Pistol Pick: Palmetto State Armory MFT Battlelink MOE EPT Pistol Lower Part Kit

Palmetto State Armory MFT Battlelink MOE EPT Pistol Lower Part Kit

If you need a lower parts kit for an AR-15 pistol, you’ll want to check out the Palmetto State Armory MFT Battlelink MOE EPT Pistol Lower Part Kit. Built to mil-spec standards, the standout features to the MFT are the rust resistant nickel coating and incredibly smooth EPT trigger.

See on Palmetto State Armory

A lower parts kit is something you will need to get if you plan on building a new AR-15 from the ground up and if you have a stripped lower receiver. The components in the lower parts kit you buy will enable you to complete your stripped lower receiver as part of your overall AR-15 set up. Alternatively, if you plan on upgrading your existing AR-15 rifle or carbine, purchasing new components for the lower receiver can serve as a vital part of that upgrade.

In this guide, we’ll dive into the merits of investing in building a new AR-15 from the ground up, which parts are included in most lower parts kit, a buyer’s guide for what to look for in a lower parts kit, and then our choices for the top three best lower parts kits that you can buy today.

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Why Should You Build A New AR-15?

There are many reasons to consider building a new AR-15 from the ground up, for which you will absolutely need to invest in a lower parts kit (assuming that you’re getting a stripped lower receiver that needs parts added).

The AR-15 is the most popular centerfire rifle in the United States today, and for good reason. It is highly accurate, reliable, ergonomic, and incredibly modular. In fact, the AR platform as a whole is one of the most customizable firearms in the world.

When buying an AR-15, you will always have two choices. You can either buy a complete AR-15 off the shelves, or, you can build your own by purchasing all of the parts you need and then putting the rifle together yourself. If you go with the latter route, you likely won’t need to buy a lower parts kit if you buy a complete lower receiver, but you will if your lower receiver is stripped (meaning that not all of the necessary parts are included).

The benefits to building your own AR-15 from the ground up are that you can truly customize your rifle, carbine, or pistol by preselecting every individual part. This will help make the rifle truly ‘your own’ rather than going with a factory made firearm.

Furthermore, building your own AR-15 from the ground up may be your only option. Gun sales have spiked dramatically this year due to uncertainty surrounding the pandemic, social unrest, and the economic recession. As a result, it can be very difficult to find an AR-15 still available for sale the factory. If this is the case in your local area, then buying each of the parts available online to build your own rifle could literally be the only choice available if you want an AR.

What Is the Lower Receiver To An AR-15?

The lower receiver is simply the lower part of your AR-15. It joins the complete upper receiver in order to create the rifle. The lower receiver specifically contains the fire control group, including the AR-15 trigger, hammer, disconnector, magazine catch, and the fire selector. It also houses the trigger assembly and the magazine.

The lower receiver is secured to the upper receiver via two pins that can be easily removed if you want to disassembly the rifle. Additional parts of the lower receiver include the magazine catch, which hold the magazine in place until depressed, the stock, and the pistol grip.

Most lower receivers are constructed using the same kind of aluminum that you find in cars, fishing reels, and aircraft (such as 6061 or 7075 aluminum). Both aluminums are very durable and strong, and yet also very lightweight. However, between the two, 7075 aluminum is undeniably the better option. For one thing, 6061 aluminum is not even mil-spec, and is not quite as tough as 7075 is. Its main saving grace is that it is more affordable.

Beyond the materials used, there are several different types of lower receivers as well. One of the most common types is the forged lower receiver, which begin as a solid piece of aluminum and are then forged into a true AR-15 lower receiver through the use of hydraulic hammers. From there, the process is completed on CNC machines.

Another common type of lower receiver is the billet lower receiver. The billet lower begins as a solid piece of aluminum as well, but does not use hydraulic hammers to transform it into an AR-15 lower. Instead, material is removed from the aluminum piece until all that remains is the fully functioning lower receiver.

As a golden rule, billet receivers cost more to make than forged lowers because more time goes into making them. However, the tradeoff is that billet lower manufacturers can really take advantages of the process to create a more aesthetically pleasing lower receiver, or otherwise a receiver that is simply more unique.

A prime example of this is the skeletonized lower receiver, which is simply a lower receiver that has a lot of the material removed until all that remains is the ‘skeleton’ of the lower. As you can imagine, the skeleton lower is much more lightweight than most other lower receivers. It’s a good choice for competition guns that involve speed.

Yet another type of lower receiver is the cast lower, which has liquid metal poured into a mold. When the materials hardens from cooling, the lower is then taken out of the cast. The finishing touches are conducted on a CNC machine.

In general, cast lower receivers are a bit weaker than billeted or forged lower receivers. This is why they are far less common, and many AR-15 manufacturers do not even bother making a cast lower receiver. No cast lower receiver is built to mil-spec standards.

What Is Included In The Lower Parts Kit?

You’re probably wondering, what’s even included in a lower parts kit in the first place? The truth is, it varies depending upon the kit.

In general, a lower parts kit is intended to come with all or most of the items that you need to turn a stripped lower receiver into a complete lower receiver, which can then be merged with a complete upper receiver to create a functioning AR-15.

Read also: Our guides on the best AR-15 side charging uppers and our favorite left-handed uppers.

However, not every lower parts kit will come with everything that you need, so it’s up to you research what is included in the specific parts kit that you are considering.

As a golden rule, you should go with a lower parts kit that includes the following items at minimum:

Item List
  • Trigger
  • Trigger Springs
  • Trigger Pins
  • Trigger Guard + Trigger Guard Assembly
  • Hammer
  • Hammer Springs
  • Hammer Pins
  • Bolt Catch
  • Bolt Catch Plunger
  • Spring
  • Roll Pin
  • Safety Selector
  • Safety Detent and Spring
  • Takedown Detents and Springs (x2 each)
  • Pivot Pin
  • Rear Takedown Pin
  • Buffer Spring
  • Buffer Retainer
  • Magazine Catch Assembly
  • Pistol Grip

Take note that some basic lower parts kits will come with each of the above items with the exceptions of the pistol grip, trigger, and trigger guard assembly. If you see a lower parts kit that is sold for a very low price (much less than most other complete lower parts kits you see for sale) chances are good that it could be missing these items.

Also take note that it can still be a good idea to purchase a new lower parts kit even if you are not building a new AR-15 or upgrading an existing one. That’s because it’s always a wise idea to have spare parts on hand, especially in the day and age we live in now where guns and gun-related parts are in much higher demand than they have been in recent memory.

Buyer’s Guide For The Best AR-15 Lower Parts Kits

These are the most important factors to consider when looking for a new lower parts kit for your AR-15:

Barrel Compatibility

Make sure that the lower parts kit you get is designed to be compatible with your AR-15 barrel. Many people overlook this aspect, because the barrel is technically a component of the upper receiver.

Mil-Spec Design

Any lower parts kit that you get should ideally be built to mil-spec standards. This means that it will be compatible with most other AR-15 lower receivers on the market, and should therefore be easy for you to install without the aid or services of a gunsmith.

A mil-spec lower receiver is any lower receiver built out of 7075 aluminum and coated in a hard coat anodized finish for solid rust and corrosion resistance. Mil-spec lower receivers are very durable, and also very common. An entire layer of aluminum oxide is formed over the entire lower, after the lower has been placed into a sulfuric acid bath and applied to an electric current.

Lower parts kit that are not of a mil-spec design are referred to as a premium lower parts kit. These kits allow for more customization, but are also much more expensive and may not be compatible with your lower receiver housing of choice.

What’s Included?

Be sure to carefully research all parts that come in your lower parts kit. Remember that not all lower parts kits include literally everything you need to complete your lower receiver. It’s up to you to research what is included.

Price

Last but not least, remember that you don’t need to exceed your budget. That’s because lower parts kits are available at a wide variety of different price points. Your goal should be to buy the highest quality parts kit that you can get for the price.

Read also: Our buying guide on AR-15 build kits. Great place to start your new build.

The 3 Best AR-15 Lower Parts Kits For 2021

Now that we’ve covered what to look for in a lower parts kit for your AR-15, here are choices for the top three best AR-15 lower parts kit in 2021:

CMMG AR-15 Lower Gunbuilder’s Lower Parts Kit

CMMG AR-15 Lower Gunbuilder’s Lower Parts Kit

If you want an inexpensive AR-15 parts kit that just comes with the bare essentials, you’ll want to give the CMMG AR-15 Lower Gunbuilder’s Lower Parts Kit a close look. This is a very basic lower parts kit that lacks a trigger, a grip, and a trigger guard. However, it includes just about every other piece that you will need for your lit.

Besides being a good choice for putting together an original lower parts kit from the ground up, you can also use this lower parts kit for the extra parts for repairs or replacements if they are ever necessary. Keep in mind that firearms and gun-related parts are flying off the shelves faster than they ever have in recent memory, so having extra parts on hand would be very wise.

Overall
All in all, the CMMG will be a great option for a basic lower parts kit with the essential parts that you need. Just be sure to also invest in a separate grip, trigger, and trigger guard.

See on Brownells

Pros
  • Relatively affordable for a lower parts kit
  • Solid choice for a basic lower parts kit
  • Good choice for buying spare or replacement parts
Cons
  • Lacks a trigger, grip, and trigger guard

Palmetto State Armory Magpul MOE Lower Build Kit

Palmetto State Armory Magpul MOE Lower Build Kit

The Palmetto State Armory Magpul MOE Lower Build Kit is built to mil-spec standards, meaning that it should be fully compatible with most other mil-spec AR-15 lower parts. All parts in this kit are specifically designed with the MOE standards in mine, or Magpul Orignal Equipment, which are very durable.

Just take note that this kit is indeed comprised of Magpul parts, so if you do not like Magpul furniture on your AR-15 this won’t be your preferred choice. The good news is that Magpul is well known in the gun world for making some of the highest quality AR-15 parts and components available, so that definitely counts for something.

Overall
If you’re looking for sturdy mil-spec lower built kit made out of high quality Magpul materials, the Palmetto State Armory MOE Lower Build Kit will be a solid pick for you.

See on Palmetto State Armory

Pros
  • Built using high quality Magpul parts
  • Mil-spec design, so compatible with most other AR-15 lowers
  • Military grade
Cons
  • Will not be the best choice if you do not like Magpul parts

Palmetto State Armory MFT Battlelink MOE EPT Pistol Lower Part Kit

If you are looking for a lower parts kit for an AR-15 pistol, you will want to pay close attention to the Palmetto State Armory MFT Battlelink MOE EPT Pistol Lower Parts Kits. This parts kit is also built using sturdy Magpul parts for solid rust and corrosion parts.

There are several feature features with the MFT. One of the best is the Enhanced Polished Trigger (EPT), which is very smooth and will help make it easier for you to fire your AR-15 pistol with faster follow up shots. The metal components to this parts kit come nickel coated for good rust and corrosion resistance as well.

Additional components in this kit include an MOE trigger guard, buffer spring, and pistol stabilizer with the addition of double sided QD points.

Overall
Overall, the MFT is an excellent choice if you need an AR-15 pistol lower parts kit. The quality nickel coating and smooth EPT fire control group are big standout features.

See on Palmetto State Armory

Pros
  • Built using sturdy Magpul parts
  • Built to mil-spec standards
  • Comes with a slick nickel coating over metal components for good rust and corrosion resistant
  • Comes with an Enhanced Polished Trigger (EPT) fire control group
Cons
  • Can’t be used for carbine or rifle AR-15s

Wrap Up

And that concludes our list of the top three best lower parts kit for an AR-15 in 2021.

Buying a new lower parts kit is something you will need to do if you want to build a new AR-15 from the ground up with a stripped lower receiver, so you need to think very carefully about the specific parts kit that will be the best choice for your AR-15.

Any one of the three lower parts kits that we have covered here today will be a solid choice for your AR-15, or alternatively, you can also follow the buyer’s guide that we outlined before to help you find a good lower parts kit as well.

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