51 of 51 Items
51 of 51 Items
Build faster, finish stronger, and avoid mismatched parts. Our AR-15 lower parts kit selection gives gun builders, from first-timers to gunsmiths, everything needed to complete a functional AR-15 lower receiver. Each kit focuses on proper fitment, reliability, durability, and interchangeability, so your lower works flawlessly with any mil-spec upper, barrel, and buttstock you choose.
All lower parts kits contain the small but essential components that make your AR's lower receiver operate. By default, our complete lower parts kits include:
Don't need the full LPK? Already got your fire controls? Missing a spring from a previous installation? We've got you covered! We also offer partial parts kits that include just springs, detents, and roll pins, and partial sets of components, so you can save money without paying twice for extra parts you don't need.
Building your AR is ultimately about enjoying an upgraded rifle (or SBR or pistol) with better components than what you'll find at the local gun shop. That's why we offer individual and upgraded lower parts to help you customize your AR-15 at the start of your build. Grab a drop-in trigger for improved accuracy out of the box. Or upgrade your basic stock and grip with Magpul's improved furniture.
Got questions about building? We've got all the answers.
Q: What parts do I need to assemble my stripped lower receiver?
A: The stripped lower receiver requires three things: A lower parts kit, a buffer tube kit, and a buttstock (for rifles and SBRs). An AR pistol can make use of a pistol brace, or you can just leave the buffer tube bare. We also sell lower build kits that include everything you need in a single kit.
Q: How do I install my lower parts kit and buffer kit?
A: Installing your lower parts kit into your stripped lower receiver or fabricated 80% lower is easy. You'll need some Roll pin punches, a gunsmith hammer, and an armorer's wrench. Use our step-by-step LPK installation guide to get the job done!
Q: What is a drop-in trigger?
A: A drop-in trigger is a self-contained, AR-type trigger assembly that contains upgraded and precisely machined version of a standard hammer, trigger, disconnector, and the required springs, inside a preassembled casing.
The entire casing drops into the lower receiver and secures using standard hammer and trigger pins. You can also use anti-walk pins. Drop-in triggers make assembling the lower easier, while providing an improved trigger and action.
Q: Does an AR pistol require a special buffer kit?
A: No. AR-15 pistols use standard buffer tubes, latch plates, castle nuts, buffers, and buffer springs. They don't use buttstocks because installing a stock on an AR pistol would convert it into a short-barreled rifle (which is illegal without first registering it).
Some builders choose to install pistol braces on their AR pistols for added stability when firing. Braces are intended to be secured to the forearm and are not intended to be shouldered like a stock.
Q: What lower parts does the AR-9 require?
A: The AR-9 lower receiver uses a standard AR-15 lower parts kit and buffer kit. The only differences are the buffer weight (the AR-9's buffer is much heavier for blowback operation), and the magazine catch, which typically comes preinstalled on 9mm lowers.
When you buy a lower parts kit for your stripped AR-9 receiver, you won't install the AR-15 magazine catch. You'll install all other components like you would on any AR-15 receiver.
Q: What lower parts kit do I need for my AR-15?
A: No matter the caliber you're chambering, all AR-15 lower receivers use the same lower parts. For example, a 5.56 NATO, 6.5 Grendel, .223 Wylde, and 300 Blackout AR-15 all use the same LPK and buffer kit.
AR-10 lowers use their own lower parts kits and buffers that contain larger components to match their larger lower receivers.
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.