California 80 Lower Laws & FAQs

Are 80 Lowers Legal in California? 

Yes! California does have certain stipulations that other states don’t have (as usual), but it is 100% legal for you to purchase, complete, and own an 80% firearm in the Sunshine State. 

From the ATF: Individuals manufacturing sporting-type firearms for their own use need not hold Federal Firearms Licenses (FFLs). However, we suggest that the manufacturer at least identify the firearm with a serial number as a safeguard in the event that the firearm is lost or stolen. Also, the firearm should be identified as required in 27 CFR 478.92 if it is sold or otherwise lawfully transferred in the future. 

If I live in California, are completed 80 lowers subject to the CA Assault Weapons ban? Do I need a bullet button? 

Completed 80% lowers are subject to all the same laws that apply to any normal firearm. If you’re unsure about what those rules and stipulations are in California, check out our blog for a step by step instruction on what to do, and most importantly what NOT to do when building an AR in California. 

And for even more information on the incredible number of CA gun laws, Calguns.net has a very helpful flowchart that you can checkout here. 

ATF Serial Number Requirements for an 80 Lower

Per federal law, an individual building a firearm for personal use is not required to mark it with a serial number. However some states (including California), have more restrictive regulations which do require you to serialize your firearm upon manufacture. Notice I said upon manufacture. Simply owning an unfinished 80% lower does not require a serial number, but the second you finish drilling and milling out your 80% lower, there better be a serial number on it. For your convenience, 80% Arms offers an 80% lower receiver serialization service, where we will serialize your completed 80% lower. However we also 80% lowers with serial numbers already on them, so there is no need to send back in your lower for engraving once it is completed. 

The following is for California residents ONLY 

In July 2016, California passed AB 857 . This legislation requires all completed firearms to have a serial number applied by Jan 1, 2019. As stated in the paragraph above, an 80% lower receiver is not a firearm, so a serial number is only required once the 80% lower receiver is completed. Again to reiterate: unfinished 80% lower receivers do not need a serial number.

If you build an 80% lower into a 100% lower receiver after July 1, 2018, you must FIRST apply to the California DOJ for a serial number, pay a fee, and they will then assign a serial number that you must apply to your firearm. If you built your firearm prior to July 2018 and already engraved a serial number of your choosing that is compliant with ATF regulations, the text of the law seems to indicate that this should be in compliance. However, we have heard that CA DOJ has made statements suggesting that people must engrave a new DOJ issued serial number on their lower even though the lower receiver already has a ATF compliant serial number engraved on it. In our personal opinion, it doesn't seem like this what AB 857 actually requires, however we are not lawyers and can't offer legal advice.  I am not a lawyer, and i highly suggest you read the law yourself and come to your own conclusion, but if you want to minimize your risk of encountering problems with the CA DOJ, it may be advisable to engrave a CA DOJ issued serial number.

Do you have to Register an 80 Lower in California? 

If you build an 80% lower and do not use a CA DOJ issued serial number after July 2018, it is a misdemeanor. Getting a serial number for a lower in CA is not the same thing as registering it as an assault weapon. That is a whole different process.

What are the ATF Requirements for Serializing a Lower? 

According to the ATF, home built rifles for personal use are not required by federal law to have a serial number. However, some people wish to engrave one anyway, or you may be required to engrave one if you live in California (see above).

For firearms manufactured in the United States by a personal firearms manufacturer, federal law requires the following information to be present:

1. A serial number (must not duplicate a previous serial number)

2. Caliber. Most individuals use “Caliber: Multi”

3. The manufacturer's name. Generally this would be your first and last name.

4. Manufacturer’s city and state. This would be the city and state in which you live.

The above information must be engraved to a depth of .003 inches and the text size must be at least .125 inches tall.

Does 80% Arms have ATF determination letter? 

Yes, we have received a letter from the ATF certifying that they do not consider our 80% lowers a firearm. You can download a copy of this letter here.

As stated previously, 80% Arms can assist you with engraving a serial number onto your completed or unfinished 80% lower. Using a high powered laser, we will ensure that your engraving is clean, precise, and holds a professional high quality look. 

How do I finish an 80% lower receiver? 

You do not need to have any machining experience in order to finish out our 80% lower receivers. All you need is a drill press, a few drills and end mills, and the 80% arms jig. You can view our step by step guide by clicking here.