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Do 80 Lowers Need Serial Numbers?

You’ve figured it out: Yes, you can legally build a gun at home. But what are the legal requirements, if any, regarding serial numbers? Does your 80 Lower need a serial number? That’s a question filled with some legalese.


“So, do 80 lowers need serial numbers?”

It depends. As far as Federal law is concerned, you do not need a serial number affixed to your 80% Lower if you’re manufacturing a firearm for yourself with no intent to sell it to anyone else.

The finished firearm must also not meet any definitions that would constitute your firearm being classified as an automatic weapon, destructive device, or other NFA item. A typical AR-15 rifle or pistol does not usually meet any of these definitions.

The Bureau of Alcohol, Tobacco, and Firearms states the following regarding the legality and serialization of 80% lowers:

“Receiver blanks (80% lowers) that do not meet the definition of a “firearm” are not subject to regulation under the GCA (Gun Control Act). The ATF has long held that items such as receiver blanks, “castings” or “machined bodies” in which the fire-control cavity area is completely solid and un-machined have not reached the “stage of manufacture” which would result in the classification of a firearm per the GCA.”

So, because your 80% Lower isn’t a firearm, you don’t need a serial number according to the ATF. However, some states do, in fact, require you to have your 80% Lower engraved with a serial number before you machine it into a firearm.

Certain states require a serial number for your 80% Lower

Some states have adopted their own legislation that requires you to submit paperwork for a serial number for your 80% Lower. California, for example, recently passed legislation (AB 857) specifically requiring all home-built firearms have a serial number by January 1, 2019.

California requires the following guidelines be adhered to when serializing your 80% Lower:
1. Markings must be at least .003” deep
2. Font size must be at least 1/16”
3. Markings must use Roman letters and Arabic numbers
4. Markings must include the serial number
5. Markings must include the weapon model
6. Markings must include the caliber
7. Markings must include the maker’s name
8. Markings must include the city and state of manufacture


Keep in mind, these requirements must be adhered to before you turn your 80% lower into a firearm.You won’t be picking your own serial number if you live under the requirements of AB 857. The California Department of Justice will assign a unique serial number for your firearm.

“Can I ever sell my 80% lower-built firearm?”

You cannot sell your 80% lower-equipped firearm without a serial number, ever. If you do wish to sell your homemade firearm at a later date, it will need to adhere to all the official regulations that govern any store-bought gun, including having an engraved serial number.

It is also important to note that once again, you cannot legally build your 80% lower with intent to sell. If, for example, you build your 80% lower with no intent to sell but eventually wish to sell it many years later, this may not necessarily constitute an original “intent to sell”, though we strongly recommend consulting an attorney first.


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 80Lower Jigs, 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.

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