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9 of 9 Items
Lower Assembly Kits for AR Builds (AR-15, AR-9, LR-308/AR-10)
If you’re finishing the “bottom half” of your AR, a complete lower assembly kit is the fastest, most reliable way to get from parts on the bench to a ready-to-pin receiver.
Our kits bundle the components you’d otherwise hunt down one-by-one (like the lower parts kit, buffer tube system, stock or brace, and small parts) so your lower is ready to meet a barreled upper with zero guesswork.
Whether you’re building your first AR-15 in 5.56/.223, a compact AR-9, or an AR-10 for longrange shooting, you’ll find proven, mil-spec options here.
Our lower assembly kits provide the full LPK (trigger, hammer, disconnector, safety, bolt catch/release, mag catch, takedown/pivot pins, detents, springs, and hardware), plus a carbine buffer tube, buffer, recoil spring, end plate, castle nut, and either a buttstock or pistol brace.
That means your serialized stripped lower (or finished 80% lower) can be fully assembled into a functional receiver that’s ready for an upper and BCG. Upgrades in select kits include enhanced triggers, Magpul® furniture, or pistol-ready SBA3-style braces, which are perfect if you want better ergonomics without that pesky SBR tax.
A complete upper assembly is the "other half" to your lower assembly. Grab an AR-15 upper, AR-10 upper, or AR-9 upper based on your assembly kit's caliber, and you'll have everything needed to finish your new rifle or pistol!
AR-15 (5.56/.223 & 300 BLK): These kits include mil-spec LPKs and carbine buffer systems that work with all AR-15 lowers.
AR-9 (9mm): Choose an AR-9 assembly kit to match your PCC build. Note the mag catch and some small parts differ from the AR-15.
LR-308/AR-10 (.308 Win): Use LR-308/AR-10 LPKs and buffer components. Note that these are not cross-compatible with AR-15 lowers; they work with the larger AR-10 lower and upper receivers.
If you’re unsure which platform you’re building, check your upper or planned caliber and match the kit accordingly. Need further assistance? Our expert customer service is here to help! Call us or email us here.
Fewer mistakes: All required parts are in one box, reducing frustrating guesswork when it comes to build.
Compatibility: Stop decoding part lists. Our kits guarantee everything works together. Just assemble and go.
Consistent fit: Our kits are built with mil-spec receivers and quality parts to ensure reliability and accuracy.
Upgrade later: An assembly kit provides the bones for upgrading your AR later, reducing upfront costs.
We've got you covered! Use our step-by-step install guide to build your lower assembly.
Deciding on what specifications or parts to use for your custom AR? We've got detailed build guides for every caliber and platform to help you pick out the right stuff:
Q: What's included in a lower assembly?
A: Every lower assembly includes a lower parts kits, buffer tube, buffer, recoil spring, end plate, castle nut, and stock or brace.
Q: Do I need an FFL to buy one one of your lower assemblies?
A: Under federal law, no. These lower assembly kits are not considered firearms under federal law. Some state laws classify these kits as firearms. We cannot ship these kits to those states. See our shipping restrictions for more information.
Q: Is the LR-308 the same as the AR-10?
A: These platforms are identical except for one small difference in the shapes of the upper and lower receivers. See our guide for more info: The AR-10 vs. LR-308.
Q: What's the difference between the AR-9 and AR-15 lower assemblies?
A: Both use the same lower parts kit, including the trigger, hammer, disconnector and safety, pistol grip, and buffer system. The AR-9 uses a heavier buffer, and its lower receiver uses GLOCK magazines with a custom magazine catch and ejector.
Q: What else is needed to complete my AR build?
A: The lower assembly kit provides the bottom half of your build. You can complete your AR with a complete upper assembly. Note the lower assemblies' included 80% lower is unfinished. It must be fabricated before installation of components.
Some states have banned 80% lowers and certain firearm parts, or have otherwise restricted the sale and ownership of the products we sell. If you cannot add a lower assembly to your cart and check out, it may be because we cannot sell our kits in your state. Please check our Shipping & Return Policy before placing an order (See Restrictions).
Your build awaits!
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.