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