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What is an 80% lower?

What is an 80% lower?

Posted by on Sep 6th 2022

Building an AR-15 (or any firearm) is an exciting project that new and experienced shooters can take on. If you're looking into building an AR-type rifle or pistol from scratch, you've probably heard of the 80% lower receiver. This unfinished firearm part is the key to fabricating a custom AR or other gun. But what is it? Here's your guide.

DISCLAIMER: We are not attorneys. State and federal firearm laws change frequently, and the products discussed herein are banned in some states. This guide cannot be taken as legal counsel. If you are unsure about the legality of buying, building, or possessing any firearm or any firearm parts in your state, seek legal counsel.

What's an 80% lower?

An 80% lower is an un-serialized firearm receiver blank. It is not operable and cannot be made to operate without additional fabrication. An un-finished 80% lower cannot accept a trigger, hammer, or safety, so it can't be made to fire a live round.

  Shop 80 Lowers

The most common type of 80% lower receiver is made for the AR-15, like the forged and anodized lower pictured above. It is an unfinished version of the AR's stripped lower receiver. These lowers (and 80% frames) exist for other rifles and handguns, like the AR9, LR-308, 1911, Sig Sauer P320, and Glock® series of handguns.

What's a stripped lower receiver?

A stripped lower receiver is the firearm component of the AR-15. That means this core component is considered a regulated firearm under federal law. Although not assembled, this receiver can function as a firearm. It can accept a lower parts kit, which includes the fire control components: The hammer, trigger, safety, disconnector, sear, pins and springs necessary to make it work. The 80% lower is the builder's alternative to buying a stripped receiver from a gun store. Cutting and drilling an 80% receiver blank for an AR-15 turns it into a stripped lower, as shown above.

Some states have banned 80% lowers

Receiver blanks are not legal in all fifty states. Some states (like California) requires a firearm receiver or frame blank to be serialized before the user fabricates one. California residents must also submit to a background before building. Other states have banned the sale, ownership, fabrication, and use of receiver blanks. Because of changing firearm laws, the below list may not be all-inclusive. These are the localities and states that have restricted or banned receiver blanks:

What can I build with 80% lowers?

The most popular 80% lower is designed for the AR-15. The original AR has many variants, configured as rifles or pistols in various calibers. In the past few years, 80% frames have now been made for different handguns. This is a current list of available 80% lowers.

AR Platform

  • AR-15 (5.56/.223, 300 BLK, 6.5 Grendel, and others)
  • AR-9 (9mm)
  • LR-308 (.308 Winchester)


This guide compares 80% lowers and frames in detail.

Frequent Questions

Q: Does an 80% lower need a serial number?

A: Under federal law, no. The ATF recommends a unique serial number be applied to your homemade firearm. That way, it can be traced more easily in the event it is lost or stolen. Some states require serialization of 80% lower receivers and frames, like California.

Q: Are 80% lowers legal under federal law?

A: Yes, they are. There's a misconception that some federal law has made unfinished firearm receivers illegal. This is false. Just like how automatic knives are only banned in certain territories and states, so too are 80% lowers. The Gun Control Act of 1968 specifically allows for the building an un-serialized firearm at home for personal use, with no license required.

Q: Are 80% lowers different from their equivalent factory-made receivers?

A: Once fabricated, an 80% lower is identical in form and function to its platform's corresponding "retail-bought" receiver or frame. This ensures parts can be installed and the firearm can be customized with popular parts.

Q: What else do I need to assemble my receiver blank?

A: Receiver blanks are sold separately from the other parts required to fabricate a firearm. In addition to the lower, you will need the appropriate parts. Here's a complete AR-15 parts guide.

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, 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.