Best AR-15 & AR-10 Lower Parts Kits (LPK)

Finishing up your AR-15 build and need a lower parts kit to finish out that stripped lower?

Aero LPK Parts
Aero LPK Parts

Nowadays…you can typically build an AR-15 that will perform better than a pre-built that costs 30-50% more.  

What’s more, you can get exactly the parts you want, and none of the ones you don’t.

A Few Of Our Personal AR-15 Uppers
A few of our favorite things…

Of course, to turn that lower into the beginnings of a rifle (or something you can slap together with a pre-existing upper assembly)…you’re going to need a lower parts kit.

Assorted AR-15 LPKs
Assorted AR-15 LPKs

It’s not sexy…but they contain all the itty bitty important parts that make your lower function like a champ.

We’ll cover what’s in a standard AR-15 LPK and our favorite picks.  Plus some AR-10 LPKs too since there’s some differences.

Table of Contents

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What’s in a Lower Parts Kit?

Specifically, you’re going to need the following:

Trigger SpringBolt Catch2 - Takedown Detents & Springs
Trigger PinBolt Catch PlungerPivot Pin
TriggerBolt Catch SpringRear Takedown Pin
Hammer SpringBolt Catch Roll PinBuffer Retainer & Spring
Hammer PinSafety SelectorMagazine Catch Assembly
HammerSafety Selector DetentTriggerguard Assembly
Disconnector & SpringSafety Selector Detent SpringPistol Grip

Now, I can feel like 75% of you losing interest immediately when confronted with that parts list but in the words of the Hitchhiker’s Guide: 

I promise it’s easier than it looks.  

In fact, you can check out the whole process of assembling a lower and decide for yourself.  If you can hammer a nail and turn a wrench, you’ve got what it takes to build a lower of your very own (and building an upper isn’t that much more involved).

Trigger Hammer Pin with Punch
Trigger Hammer Pin with Punch

Wondering which one to pick?  Where to buy them? What to do if you already have a trigger?

Fear not, firearms aficionados.  

I’ve got you covered.

Best AR-15 Lower Parts Kits

These are the best lower parts kits out there and are the ones I keep coming back to for build after build. 

1. Palmetto State Armory

Palmetto State Armory might sell the most AR-15s in the country…so they are one of my go-to sources for anything AR-15.

PSA .224 Valkyrie At High Bar Homestead
PSA .224 Valkyrie At High Bar Homestead

I’ve built plenty of their lowers with their LPKs.  Check out all our reviews of their guns here.

PSA LPK
PSA LPK

It may not look like much…but the baggies are a lifesaver…they are broken down into areas of lower assembly.  So now you don’t have to guess which spring or detent is which.

And almost all their kits come with additional furniture…I particularly like their Magpul MOE sets since I would have added one anyways.

55
at Palmetto State Armory

Prices accurate at time of writing

Prices accurate at time of writing

Also note that most lower parts kits don’t come with buffer tube assemblies so PSA has those “complete” sets too.

100
at Palmetto State Armory

Prices accurate at time of writing

Prices accurate at time of writing

Check out the entire selection of build kits and LPKs.  Some have their upgraded EPT trigger which is Nickel Boron coated (silver colored) for better trigger feel.

What’s your take on the PSA LPK?

Readers' Ratings

4.99/5 (160)

Your Rating?

2. Brownells MOE

Brownells is the premier online retailer of gun parts and accessories, so it makes sense that they would have an LPK for sale. The Brownells MOE AR-15 Lower Parts Kit actually comes with the buffer assembly, and Magpul MOE stock and grip, as well as an Geissele trigger, which is why it is so expensive compared to others.

230
at Brownells

Prices accurate at time of writing

Prices accurate at time of writing

This kit is great if you’re looking for getting some good parts out of the gate and don’t want to spend a lot of time picking out parts.  In other words, if you’re here more for the building than for the savings or the part picking, this is the way to go.

Not that these parts are bad, and it’s certainly very convenient to have everything you need to complete the lower in one contained package (and it’s over Brownell’s free shipping threshold too) but you can get better parts and save money if you shop individually.

3. Geissele Automatics Lower Parts Kit

Speaking of Geissele…they are known mostly for their triggers, muzzle devices, and handguards, but they make everything from complete rifles to parts kits as well.

And the Geissele parts kit is pretty great.

It’s precision machined with all the skill and accuracy you’d expect from Geissele, and the price isn’t half bad for a set this nice.  The only things that are missing are the pistol grip and trigger group.

Best Trigger-less LPK
50
at Brownells

Prices accurate at time of writing

Prices accurate at time of writing

I’d personally recommend throwing your favorite grip on there, and coupling that with a matching Geissele SSA-E trigger, or some other equally awesome Geissele offering.

4. Aero Precision Lower Parts Kit

Looking for something no-frills when you already have everything else like the trigger and pistol grip?

Aero LPK
Aero LPK

The Aero LPK gets the job done at an affordable price of $25.

Aero LPK Parts
Aero LPK Parts

They’ve also done well in my Aero, Anderson, and PSA lower builds.

25
at Aero Precision

Prices accurate at time of writing

Prices accurate at time of writing

Looking for a more standard LPK with trigger and pistol grip?
60
at Aero Precision

Prices accurate at time of writing

Prices accurate at time of writing

5. CMMG LPK

Another huge manufacturer of AR-15 parts and LPKs…CMMG.
CMMG LPK
CMMG LPK

They also come with baggies…but theirs are color coded with a legend in the back of the box to tell you specifically what’s there.

CMMG LPK with Colored Baggies
CMMG LPK with Colored Baggies

Highly recommend the CMMG LPK for a first time builder who isn’t looking to upgrade their trigger and pistol grip just yet.

Now let’s move onto the AR-15’s big bro…the AR-10.

Best AR-10 Lower Parts Kits

Most AR-15 LPKs will work with the AR-10.  But since the AR-10 is shooting larger calibers, the receiver and magazines are much larger.

Because of that these are a few of the parts that are NOT interchangeable.

  • Bolt Catch
  • Bolt Catch Roll Pin
  • Pivot Pin
  • Takedown Pin
  • Buffer
  • Buffer Spring
  • Magazine Catch

There’s also two “patterns” of AR-10 lower receivers.  By far the most common is the DPMS variant.  Unless yours says it is the Armalite style…chances are it’s the DPMS.

1. DPMS AR-10 Lower Parts Kit

And because of that…we recommend going with the source of the receiver pattern.

86
at Brownells

Prices accurate at time of writing

Prices accurate at time of writing

2. CMMG AR-10 Lower Parts Kit

Consistent with our AR-15 recommendations, we like CMMG’s AR-10 LPK.  My first AR-10 lower used one and it worked fine.

80
at Palmetto State Armory

Prices accurate at time of writing

Prices accurate at time of writing

3. PSA AR-10 Lower Parts Kit

PSA’s AR-10 is proprietary and works great (full review here), but their LPK works with DPMS patterned AR-10s from other manufacturers.

120
at Palmetto State Armory

Prices accurate at time of writing

Prices accurate at time of writing

They also have tons of other packages with different triggers and grips.

What If You Lose Parts?

Well, you could just order the part, probably from Brownells or the like, but shipping for one part is annoying.

If you’re going to make a hobby out of this, you are almost guaranteed to lose parts (springs and detents will go flying across the garage at some point), so it may make sense to invest in a spare parts kit like this one.  

Best Build Saver
8
at Cabelas

Prices accurate at time of writing

Prices accurate at time of writing

This kit gives you a spare of all the little springs and other fiddly parts you’ll need, as well as spares for when springs start to wear out and break down.

Upgrading From Standard Parts

Finally, I want to make a note about upgrading these parts kits.  Granted, a spring is a spring, but an upgraded trigger, buffer, grip, and stock can really make a huge difference in how your rifle performs.

The trigger is really going to be the single biggest performance factor for the speed and accuracy of your gun.

Tested AR-15 Triggers
Tested AR-15 Triggers

We’re coming out with a major update to our trigger recommendations, but for now these are the Best Drop-in AR-15 Triggers.

After that, start with your furniture and go with something like Bravo Company or Magpul, in whatever color and design you like, and at whatever price point matches your build goal.  See our favorites in Best AR-15 Furniture.

Parting Shots

That does it for lower parts kits.  You should now know what to look for, how to choose a lower parts kit, and what to buy, as well as how to move on from the standard parts kits.  

If you’re building a rifle, and you’ve got your lower, this should get you the rest of the way to completing it.

Don’t forget about taking a look at the Best AR-15 Upgrades [2018]!

Building a rifle?  Like these parts kits?  Hate these parts kits? Got questions?  Let me know in the comments below!

12 Leave a Reply

  • Andy M.

    Thanks for an article about a very overlooked area of builds. I have wondered quite often what expensive LPKs have going for them that budget LPKs don’t? And your input seems to confirm my personal opinion as a builder, as long as their in spec... nothing really different. However, I would like to mention my favorite LPK, and the only one that really stands about as being a little better/different... the STRIKE INDUSTRIES ENHANCED LPK. $40 w/o fcg & grip. Better mag release, bolt catch, & takedown/pivot pins than standard.

    4 months ago
  • David

    What about the CMMG kits vs Geissele? Also from a comment you made to someone else, it’s sounds like quality is mostly irrelevant as long that the parts are the right size/spec??? Did I understad that correctly??? Is the listed “oops” kit good enough quality you could take a Geissele kit, swap in all the “oops” kit parts and still feel 100% secure it will function as well??? Or was that a cheap oops option, but buying an extra lpk or 2 from Geissele to use as “oops” components be best for a patrol or PDW build that your and others lives will depend on??? Like the other person kinda eluded to, I’d love to know more about which parts Geissele makes vs which ones they get from a common supplier that you would find in many companies kits. But I loved the article!!! Thanks!!!

    6 months ago
    • David, PPT Editor

      I've tried 6 or 7 different LPKs over the years, I've never had an issue with any of them in terms of long term durability. I have gotten ones that were flatly not sized right, but all I had to do was contact the retailer and was sent new ones. Even with "Opps Kits" I've never found a difference in the long term. There are finish differences, Geissele, Aero, and CMMG have always installed very smoothly and quickly for me. Anderson was a little rough but still worked. I don't know exactly part for part who makes what. Your best bet for that info would be to contact each of them and ask, but they might not release that information.

      6 months ago
  • operator1961

    Any opinion on the Wilson Combat LPK?

    6 months ago
    • David, PPT Editor

      I would highly recommend anything by Wilson Combat. Their Beretta parts, AR parts, 1911 parts, everything they make is outstanding. And their LPK is surprisingly well priced too.

      6 months ago
  • Michael

    Does anyone know how the Aero Precision LPK compares to these?

    6 months ago
    • David, PPT Editor

      Highly recommend Aero LPKs. I've used them in several builds and have never had an issue.

      6 months ago
  • David Nuckols

    excellent piece - thanks for the info

    9 months ago
  • Jim

    I went the way of a PSA Magpul LPK, came with absolutely everything. Stock, Buffer Tube, Buffer and Buffer Spring and all of the little parts. The only thing that I would think about upgrading would be the trigger. All for a little over $100.

    10 months ago
  • Bravo Tango

    When I comment on one of these, I generally try to further the conversation, not to be critical. That being said, I don't see anywhere in this article that teaches how to choose an LPK, other than by price or the ones you like. Is there some info you can share on determining quality by materials used or how the parts are manufactured, i.e. forged, milled, cold wound springs, etc.? If not, I understand. If nothing else, you could emphasize using customer reviews as a tool to determine absolute quality or "bang for your buck". Thank you for sharing what you have thus far. I appreciate all the help I can get.

    10 months ago
    • David L

      Sadly this is one of those areas where it is very hard to tell who or how the parts were actually made. Many of the large brands don't actually make the parts themselves while still others make the parts themselves and for other major brands. Generally speaking though, since none of these parts is pressure bearing or have much mechanical value to them, they are unlikely to wear out or break even after tens of thousands of rounds. The main issue is that they need to be in spec from the start, but even that is mostly for installation rather than durability. My main goals when picking an LPK is that it comes with what I want (I generally get ones that do NOT have an FCG since I use aftermarket triggers), it is a decent price (around $50 or less), and that I get it from a company or retailer that I know has good customer service. I've had to return 2 kits for not being in spec, one was from a very good name brand and the other from a random no name. The no name about 80% of the parts were out of spec and the good brand only 1 part was out so they just sent me an oops kit to replace it.

      10 months ago
  • Tyler

    How do you feel about the Anderson lower kit? I just recently built a lower using the stainless steel trigger kit and I'm liking it so far.

    10 months ago
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