Best AR-15 Lower Parts Kits

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

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.

Lower Receiver and Its Working Parts
Your Lower Receiver and Its Intricate Working Parts

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 LPK and our favorite picks.

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).

But what, I hear you saying, about all those little parts?  

Well, many manufacturers have recognized what a pain in the posterior it would be to chase down all those little springs, detents, and what not, not to mention the expense that would be involved in shipping them all, so there are parts kits out there that include all of them.

These lower parts kits will include everything you need to finish that stripped lower, and when you’re done you’ll be able to slap an upper on it and go shooting.

Editor's Pick (Forged)
50
at Brownells

Prices accurate at time of writing

Prices accurate at time of writing

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.

See, I’ve built well over a hundred rifles, some for work, some for personal use, and I’ve used and tested literally every LPK that’s available today.  I can tell you what to look for, where to buy them, and what parts to replace to get the most out of your shiny new rifle.

Interested?

Let’s get started.

Choosing a Lower Parts Kit

You’d think that lower parts kits were all the same, I mean how many different ways are there to make a spring, right?

Well, there are some differences, and they can affect the price of your lower build dramatically, and even screw up your build if you aren’t careful, so it’s important to understand the differences.

First, you need to know that most parts kits won’t include the buffer tube, buffer, buffer spring, or stock assembly, so those will have to be purchased on the side.  This is just something to be aware of when you’re pricing your build.

A cheap stock assembly kit that will include all of these parts including a basic mil-spec stock will run you about $40.  Taking that into consideration, it may be cheaper to just buy a complete lower, rather than a stripped lower, LPK, and stock assembly.  

150
at PSA

Prices accurate at time of writing

Prices accurate at time of writing

You’ll have to price that for yourself, but its most likely that buying the three separately will save you some money, and will certainly give you an easier time choosing the parts you want which ones to upgrade.

For me, I’m almost never building a “cheapest of the cheap” gun, and I want a certain stock and a good trigger for all my guns, so I don’t like going solely on price anyway.  A gun that’s no fun to shoot is a much worse investment than a gun that costs $50 more and is a blast.

Which leads to my next point, and that is that some of the parts on your lower, particularly the pistol grip, stock, and trigger, will have an enormous impact on the accuracy of your gun, as well as your comfort when shooting it.

Our 12 Best AR-15 Stocks [Hands-on] article has some great recommendations when it comes to finding the perfect stock for you.

A gun with the ergonomics of a brick is no fun, and not worth the time, money, and effort spent on it.  Make sure you’re getting the parts you want, which might mean buying a trigger-less LPK so that you can drop that sweet 3Gun or single-stage precision trigger in it.  

You may also want to buy a buffer tube assembly and stock separately so you can get the exact buffer weight (which will dramatically impact felt recoil) and stock (which will dramatically affect ergonomics and shooter comfort) that you want.

Best 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.  These are repackaged and rebranded by some folks, but its best to try and get them from the original manufacturers when you can…cheaper that way too.

1. DPMS AR-15 Lower Parts Kit

The DPMS AR-15 lower parts kit is pretty much the standard-issue LPK for many folks.

This is a full set of mil-spec parts that is perfect if you’re looking for the cheapest of the cheap builds, building rifles in bulk (look, I don’t wanna know why you’re stockpiling them, but don’t do anything illegal with them, okay?), or stocking them for sale in a store.

Best Complete LPK
65
at Brownells

Prices accurate at time of writing

Prices accurate at time of writing

This kit includes everything but the stock and buffers assembly, but you can easily pick up a mil-spec buffer and stock for about $30 more, less if you shop around a bit, or have a spare left over from another build that got upgraded.

I’ve used this kit probably thirty times, maybe more,  and while it isn’t the best, and the trigger is way less than great, it is perfectly serviceable, and will do just fine if you’re building a rifle on the cheap.

You can also get a trigger-less version which will allow you to install a better trigger out of the box without worrying about having a spare lying around.

If you’re anything like me, spare rifle parts are dangerous and have a way of turning into spare complete rifles…much to the detriment of my wallet and relationship to my significant other.

2. Brownells MOE AR15 Lower Parts Kit

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 ALG Defense 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.

The ALG trigger and the MOE furniture are certainly a far sight better than standard mil-spec furniture, but you’ll have to decide if that’s worth it.

3. Geissele Automatics Lower Parts Kit

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

Best Trigger-less LPK
50
at Brownells

Prices accurate at time of writing

Prices accurate at time of writing

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.

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.

What’s your take on the Geissele LPK?

Readers' Ratings

4.99/5 (154)

Your Rating?

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.  That said, sometimes that’s the only way, and most places will drop it in a cheap bubble mailer for you.

However, 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.  If you’re going to get serious about this as a hobby, I highly recommend grabbing one of these.

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. We’re coming out with a major update to our trigger recommendations, but for now these are the 6 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.

Next, tuning your buffer weight to your rifle can dramatically reduce felt recoil and improve your shooting experience.  This is especially important and especially useful if you have an adjustable gas block.

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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