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 Golden 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 best 80% lower are subject to all the same laws that apply to any normal firearm. If you live in CA, you need to be careful to follow the laws related to the assault weapons ban. In general, if you build AR-15 style rifle with a pistol grip, you will need a device that prevents the removal of the magazine without disassembly of the action. A “bullet button” no longer counts to make the rifle California compliant. There are also “featureless” configurations that do not require a device to lock the magazine in place while the action is assembled. Check out our blog post on featureless rifles 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 check out 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 sell 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.