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  • Mil-Spec AR15 Lower Parts Kit (w/ Hammer and Trigger)

    Mil-Spec AR15 Lower Parts Kit (w/ Hammer and Trigger)

    Want an AR-15 trigger that suffers no creep, take-up, or over-travel? Looking for the easiest-to-install LPK? How about the most affordable parts kit possible? This mil-spec AR-15 LPK comes in at a great price with machining and performance that feels...

    $39.99
  • AR15 LPK Missing Parts Kit

    AR15 LPK Missing Parts Kit

    This AR15 LPK Missing Parts Kit has all the essentials for any lost parts, replacement parts, or for your next custom build. All parts are proudly made in the USA. This LPK Missing Parts Kit comes with: (1) buffer retainer (1) buffer retainer spring (1)...

    $11.99
  • KAK-308-LPK

    LR-308/AR-10 Lower Parts Kit (w/ Hammer and Trigger)

    We strive to provide accurate photographs of our product. Due to parts availability, this kit's trigger and hammer may come in stainless or black. Want an LR-308 trigger that suffers no creep, take-up, or over-travel? Looking for the easiest-to-install...

    $49.99
  • Premium AR-15 Lower Parts Kit Premium AR-15 Lower Parts Kit 2 Premium AR-15 Lower Parts Kit 3 Premium AR-15 Lower Parts Kit 4

    Premium AR-15 Lower Parts Kit

    A lower parts kit is essential to finishing your AR-type 80% lower or FFL-bought stripped lower receiver. This upgraded LPK maintains mil-spec fitment, but it also comes with a MagPul pistol grip and Magpul MOE trigger guard. This Lower Parts Kit...

    $64.99
  • AR15 LPK - Basic Build Kit

    AR15 LPK - Basic Build Kit

    The Kak Industry AR15 Lower Parts Kit comes with all of the basic essentials you'll need for your own custom AR15 build. This build kit includes the following: bolt catch kit magazine catch kit hammer & trigger pins pivot pin & detent &...

    $26.99
  • Magpul®  MOE® Enhanced AR15/M4 Polymer Trigger Guard Magpul®  MOE® Enhanced AR15/M4 Polymer Trigger Guard Magpul®  MOE® Enhanced AR15/M4 Polymer Trigger Guard

    Magpul® MOE® Enhanced AR15/M4 Polymer Trigger Guard

    The Magpul® MOE® Enhanced Trigger Guard is a simple but effective customization that can improve your AR's lower. It provides more room in the trigger well for gloved fingers, and installation is simple: This guard doesn't require any punches or...

    $8.99
  • AR15 Pin & Detent Parts Kit

    AR15 Pin & Detent Parts Kit

    The KAK Industry AR15 Pin & Detent Parts Kit is made out of the best parts on the market. This kit is great for replacement parts, a new build, or having spare parts. This kit includes: a pivot pin takedown pin pivot and takedown detents hammer and...

    $19.99
  • Strike Industries Enhanced Lower Parts Kit

    Strike Industries Enhanced Lower Parts Kit

    The Strike Industries Enhanced Lower Parts Kit is an excellent mil-spec+ LPK. It includes an ambidextruous safety selector and quality, machined components that provide smooth, reliable operation. Additional Features: Enhanced Bolt Catch Strike Magazine...

    $72.95
  • AR-9 Ejector AR-9 Ejector 2

    AR9 Replacement Ejector w/ Screws

    This is a replacement ejector for our AR9 80% lower receiver. Features: Fits ZR9 & New Frontier Armory Pattern AR-9 PCC Made from 17-4 Stainless Steel hardened to RC42 Includes 2 cap screws

    $11.99
  • Spike's Tactical Lower Parts Kit for .223/5.56

    Spike's Tactical Lower Parts Kit for .223/5.56

    The Spike's Tactical Lower Parts Kit provides reliable operation inside any AR-15's 80% lower or stripped lower receiver without breaking your budget. Its mil-spec fitment and springs ensure you get a clean, repeatable trigger and hammer reset for good...

    $71.96
  • AR9 Replacement Mag Catch AR9 Replacement Mag Catch 2 AR9 Replacement Mag Catch 3 AR9 Replacement Mag Catch 4

    AR9 Replacement Mag Catch

    This is the replacement magazine catch for our AR9 80% lower receiver. Features: Billet aluminum catch Dowel pin and capture set screw included

    $29.99
  • Aero Precision AR15 Enhanced Lower Parts Kit

    Aero Precision AR15 Enhanced Lower Parts Kit

    Aero Precision's Enhanced LPK includes some simple but effective upgrades, like a Magpul MOE pistol grip, and custom billet trigger guard. This kit includes precisely CNC-machined components with tight tolerances to ensure reliable operation once...

    $67.99
  • Aero Precision M5 .308 Standard Lower Parts Kit

    Aero Precision M5 .308 Standard Lower Parts Kit

    If you're starting an LR-308 build, you'll need a good lower parts kit. Aero Precision makes a lower parts kit designed for their M5, which is Aero Precision's version of a .308 AR. This high-quality M5 LPK is also compatible with our LR-308 80% lowers...

    $85.99
  • Aero Precision M5 .308 Enhanced Lower Parts Kit

    Aero Precision M5 .308 Enhanced Lower Parts Kit

    If you're starting an LR-308 build, you'll need a lower parts kit. How about an LPK with an upgraded grip?. Aero Precision's M5 Enhanced .308 Lower Parts Kit provides just that: Quality, mil-spec internals for your stripped lower receiver, or finished ...

    $104.99
  • Spike's Tactical - AR-308 Lower Parts Kit

    Spike's Tactical - AR-308 Lower Parts Kit

    The Spike's Tactical AR-308 Lower Parts Kit sports military-grade hardware (minus that third safety position) with a great fit and finish. This kit is compatible with both retail-bought .308 stripped lowers, and .308 80% lower receivers. What's...

    $64.80
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The lower parts kit (LPK) is one of the most important parts of any AR build. The LPK includes all the parts necessary to chamber a round, flip the safety, squeeze the trigger, and fire a round downrange using your AR-15 lower. A lower parts kit is absolutely necessary to convert your 80% lower receiver (or retail-purchased stripped lower) from a piece of aluminum or polymer to a fully-functioning firearm, quickly and cost-effectively.

Not sure which LPK you need for your AR? Read the parts kit compatibility guide!

Need help with assembly?

We wrote the ultimate guide on how to install the AR-15 lower parts kit. Follow these step-by-step instructions to assemble your lower receiver.

The Lower Parts Kit: What's Included

All lower parts kits include the following components for assembling the lower receiver, ordered alphabetically:

  • Bolt Catch
  • Bolt Catch Plunger 
  • Bolt Catch Roll Pin
  • Bolt Catch Spring
  • Buffer Retainer
  • Buffer Retainer Spring
  • Disconnector
  • Disconnector Spring
  • Hammer
  • Hammer Pin
  • Hammer Spring
  • Magazine Catch
  • Magazine Catch Button
  • Magazine Catch Spring
  • Pistol Grip
  • Pistol Grip Lock Washer
  • Pistol Grip Screw
  • Pivot Pin
  • Pivot Pin Detent
  • Pivot Pin Detent Spring
  • Safety Selector Lever
  • Safety Lever Detent 
  • Safety Lever Detent Spring
  • Takedown Pin (Front/Rear)
  • Takedown Pin Detent 
  • Takedown Detent Springs
  • Trigger
  • Trigger Guard
  • Trigger Guard Roll Pin
  • Trigger Pin
  • Trigger Spring

Additional Parts Required for Install

To complete the AR-15 lower parts kit install, you will also need a castle nut and latch plate. These two components are not usually included with the LPK but they are required for securing the safety lever detent and spring, and the buffer tube. They typically come with your tube or buttstock assembly instead. An LPK and buttstock combo kit is available.  If you already have a parts kit, simply grab the buttstock, tube, nut and plate here.

AR-10 and Pistol Parts Kits

We cater to all AR platforms, 80% builds, and calibers, so we've sourced quality parts kits for your pistol-caliber carbines and AR-9s, and your 1911, Glock-compatible, and Sig handgun builds. Want to throw more lead downrange with your black rifle? Grab a regular AR-15 LPK for your 6.5 Creedmoor or .308 AR-10 project. All 5.56/.223 parts kits are designed to work with both retail-purchased .308 stripped receivers and our LR-308 80% lower receivers. In fact, virtually all AR-type weapons use an AR-15 LPK!

Here's a detailed guide covering LPK compatibility.

Need help completing your .308 build?

Converting to Drop-in Triggers

One of the easiest upgrades any AR owner can do is swap out that factory hammer and trigger for a drop-in trigger. These custom, self-contained fire control units include a new hammer, trigger, disconnector, and sear. They quite literally drop into the lower receiver once a factory parts kit has been installed. Just punch out the hammer and trigger pins, remove the trigger, hammer, disconnector, and springs, drop the new trigger assembly in, and replace the pins. It's incredibly easy and takes just a few minutes. Pick up a quality upgraded drop-in trigger here. It'll help tighten up your groupings and make for quicker follow-up shots.


DISCLAIMER: If you are new to the world of DIY gun building, you likely have a lot of questions and rightfully so. It’s an area that has a lot of questions that, without the correct answers, could have some serious implications. At 80-Lower.com, we are by no means providing this content on our website to serve as legal advice or legal counsel. We encourage each and every builder to perform their own research around their respective State laws as well as educating themselves on the Federal laws. When performing your own research, please be sure that you are getting your information from a reliable source.

We are a national retailer of individual components and not all products depicted on this website are legal in every state. Shipping of various products found on this website are prohibited to some states (such as California, Connecticut, District of Columbia, Hawaii, New Jersey, New York, Rhode Island, and Washington). The information, pictures, text or products presented on this website are not a representation by us, and should not be understood by you, that any product or completed firearm is legal to assemble or own in your state of residence. We encourage each and every builder to perform their own research about the state and federal laws that apply to them. It is your responsibility to understand the law and we encourage you to consult with an attorney or your local ATF representative.