[cjhveal]

It's definitely not 100% unregulated to produce your own firearm in the United States. It can be very very illegal to do so and it's a really dangerous piece of advice to be giving a bunch of hackers. You must obey state and municipal laws regarding your eligibility to own a firearm at all. The firearm itself must be legal according to your state law. In the entire country, you must apply to the DOJ for a serial number before completion of the firearm and you must have it permanently engraved or imprinted upon the receiver or a piece of embedded steel.

[rsj_hn]

> In the entire country, you must apply to the DOJ for a serial number before completion of the firearm

This is incorrect and is itself "bad advice". You do not need a serial number from the DOJ if you are not selling. But as has been stated in the comments, CA does have more stringent local rules and I'll update my comment to reflect that. I also added a link that explains the situation.

[cjhveal]

You're correct on the facts here as they relate to federal law-- I was reacting to the post's previous mention that firearm manufacture for personal use was 100% unregulated by any existing law. You've since edited it to be much more accurate and my comment isn't necessary.

[seany]

The serial number part of this comment is only true if you want to sell a firearm you've made. If you built it for yourself undersized is perfectly fine (at the national level).

You also only have to apply for anything unless you become a manufacturer.

[Rebelgecko]

In California you have to buy serial numbers from the government, even if the manufacturing is just for personal use. There's also laws that make it illegal to make guns out of certain materials, and any pistol/handgun is basically required to be single shot/bolt action.