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19 of 19 Items
  • Sale
    Mil-Spec AR15 Lower Parts Kit (w/ Hammer and Trigger)

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

    This LPK offers the parts needed to finish your lower, and for a fraction of the cost of a "retail" bought assembly. This lower parts kit comes with all the internal parts needed to finish your lower, from the pivot pin to the trigger. With this kit...

    Was: $46.79
    Now: $38.99
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    AR15 LPK - Missing Parts Kit by KAK

    AR15 LPK - Missing Parts Kit

    The AR15 Missing Parts Kit is perfect for any lost parts, replacement parts, or for your next custom build. What's Included? Buffer retainer (1) Bolt catch spring (2) Bolt catch detent (1) Selector detent (2) Disconnector spring (2) Buffer retainer...

    Was: $11.99
    Now: $9.99
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    LR-308/AR-10 Lower Parts Kit (w/ Hammer and Trigger)

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

    We strive to provide the most accurate photographs of our product whenever possible. Due to availability limitations and supply chain constraints, slight variations of the trigger and hammer finsh (stainless or black) may occur.  If you're looking...

    Was: $76.79
    Now: $63.99
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    AR15 LPK - Basic Build Kit

    AR15 LPK - Basic Build Kit

    This AR15 Basic Lower Parts Kit includes all of the basic necessities needed for your own custom build. Most importantly what comes with this kit are the following, a bolt catch kit, magazine catch kit, takedown pin & detent & spring, pivot pin...

    Was: $32.39
    Now: $26.99
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    MOE® Enhanced AR15/M4 Polymer Trigger Guard by Magpul® MOE® Enhanced AR15/M4 Polymer Trigger Guard by Magpul® MOE® Enhanced AR15/M4 Polymer Trigger Guard by Magpul®

    Magpul® MOE® Enhanced AR15/M4 Polymer Trigger Guard

    Stop installing that boring mil-spec trigger guard on every AR you build. The Magpul® MOE® Enhanced AR15/M4 Polymer Trigger Guard is miles ahead of the mil-spec stuff. Why? For starters, it's extremely ergonomic and gives your trigger finger a...

    Was: $10.79
    Now: $8.99
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    Enhanced Lower Parts Kit by Strike Industries

    Enhanced Lower Parts Kit by Strike Industries

    If your .223 or 5.56mm AR-15's lower parts kit is worn out needs replaced, or if you just want to refresh the controls on your rifle, you need to get the Strike Industries Enhanced Lower Parts Kit. It'll rejuvenate your lower assembly and also has the...

    Was: $87.54
    Now: $72.95
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    AR15 Enhanced Lower Parts Kit by Aero Precision

    AR15 Enhanced Lower Parts Kit by Aero Precision

    For your next AR-15 build, you should start your lower receiver with a quality lower parts kit, so you don't just end up replacing it later. With that in mind, Aero Precision gives you their AR-15 Enhanced Lower Parts Kit to start your build off in a...

    Was: $81.59
    Now: $67.99
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    M5 .308 Standard Lower Parts Kit by Aero Precision

    M5 .308 Standard Lower Parts Kit by Aero Precision

    If you plan to start an LR-308 build, you're gonna need a good lower parts kit. Aero Precision makes a lower parts kit designed for their M5, which is their own proprietarily designed .308 rifle that can also work with your LR-308 build, provided yours...

    Was: $81.59
    Now: $67.99
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    AR15 LPK Pin And Detent Kit by KAK

    AR15 LPK Pin And Detent Kit by KAK

    The KAK Industry AR15 Pin And Detent Lower Parts Kit was manufactured with top of the line materials for the best quality parts. This kit is great for replacement parts, a new build, or having spare parts. This kit comes with a pivot pin, takedown pin,...

    Was: $23.99
    Now: $19.99
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    Aero Precision Enhanced Lower Parts Kit - M5, .308

    Aero Precision Enhanced Lower Parts Kit - M5, .308

    If you're planning an LR-308 build, a good lower parts kit is on your to-buy list. It'd also be nice if your lower parts kit came with a more comfortable grip than the standard A2 grip. Aero Precision makes a lower parts kit designed for their own M5, a ...

    Was: $101.99
    Now: $84.99
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    NiB-X Lower Parts Kit, Mod 3 by WMD Guns

    WMD Guns NiB-X Lower Parts Kit, Mod 3

    You know, you can get more out of your AR shooting experience even just by making minor changes to your AR's lower parts kit. This lower parts kit by WMD Guns is mil-spec save for one detail: the trigger, hammer, and disconnector have all been coated in...

    Was: $107.99
    Now: $89.99
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    AR-15 Lower Parts Kit Without Trigger - Spike's Tactical

    AR-15 Lower Parts Kit Without Trigger - Spike's Tactical

    The Spike's Tactical AR-15 Lower Parts Kit is made out of top of the line parts that don't compare to others on the market, allowing users to attain the most longevity. This LPK includes a Mil-Spec bolt catch, mag catch, mag catch button, Mil-Spec...

    Was: $137.99
    Now: $114.99
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    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 a key part to finishing your lower. It's one of the most important aspects of your AR-15 as far as quality is concerned. This lower parts kit offers all the parts needed to finish your stripped receiver. You'll also need an upper...

    Was: $77.99
    Now: $64.99
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    AR-308 Lower Parts Kit - Spike's Tactical

    Spike's Tactical - AR-308 Lower Parts Kit

    The Spike's Tactical AR-308 Lower Parts Kit has a great fit and finish along with a military grade design that is built to last. This parts kit is meant to be used with Spike's Tactical's forged sets and may not be compatible with any other large frame...

    Was: $77.76
    Now: $64.80
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    Lower Parts Kit for .223/5.56 by Spike's Tactical

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

    The mil-spec lower parts kit is adequate. It does the job it was designed for. The trigger, hammer, disconnector, detents, springs, and roll pins are perfectly suited to the job of making your lower (and the rest of your AR) work as intended. As with the...

    Was: $86.35
    Now: $71.96
19 of 19 Items

Quality, U.S.-made AR-15 lower parts kits.

The lower parts kit - which contains your AR-15's hammer, trigger, safety, and disconnector - make or break the overall "feel" of your black rifle or pistol. A poorly machined trigger and hammer will make for a poor trigger pull. We only work with the country's best gunsmiths and manufacturers to provide quality, mil-spec AR lower parts kits for all your AR builds.

Lower Parts Kits: What's Included

A complete lower parts kit includes the following components which are necessary to assemble any AR lower you fabricated with an 80% jig, or FFL-bought stripped lower receiver:

  • Hammer
  • Hammer spring
  • Trigger
  • Trigger
  • Disconnector
  • Disconnector spring
  • Buffer retainer
  • Buffer retainer spring
  • Magazine catch
  • Magazine release button
  • Magazine catch spring
  • Bolt catch
  • Bolt catch spring
  • Front pivot pin
  • Rear takedown pin
  • Hardware retaining dents
  • Hardware retaining springs
  • Pistol grip
  • Pistol grip washer/screw

How to Install The Lower Parts Kit

Need help? Follow our LPK install guide step by step.

Our guide covers every step in detail, with pictures. We cover how to install the hammer, trigger, safety, and all pins and springs, plus the other parts required to fully assemble your lower before installing your upper receiver.

What else is needed to assemble my lower?

Most lower parts kits do not include the buffer assembly, which is required for the upper receiver to operate and cycle rounds via the bolt and recoil spring. Grab a buffer tube or full buffer kit that include the recoil spring, buffer, castle nut before attempting your installation. 

As shown in our install guide, we also strongly recommend investing in a set of roll pin punches and gunsmith hammer.

Parts Kits for Other AR Calibers

Thankfully, the AR-15's various calibers all utilize the same parts kits. Even .308-receiver builds, like the .308 Winchester and 6.5 Creedmoor, use mostly AR-15 components in the parts kits. We have a quality .308/AR-10 parts kit for those builds available here. Building anything like a 300 Blackout, 9mm (AR9), 6.5 Grendel or regular old 5.56/.223 gun? Grab a standard AR-15 parts kit! They all use the same LPKs and buffer assemblies.

Upgrade that latch plate

The latch plate is the unit that retains the safety lever hardware with the buffer tube. It's also the perfect place for a quick-detach swivel sling mount. We've sourced some quality upgraded latch plates that provide multiple sling mounts and fold-out function for your buttstock and buffer, like the Sylvan Arms Folding Stock Adapter.

 


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 GunBuilders.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.