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How to Legally Build an AR Pistol in CA

This one’s a tough field of legal mines to navigate. We’ll keep the introductions simple, here: Yes, you can legally build an AR pistol in CA – you just have to be very specific and careful about how you do it. Let’s go over the legal requirements you must consider before even getting started:

  1. Build your AR Pistol using a dedicated pistol receiver or an 80% lower.

Never, ever build your AR pistol using a lower from a rifle. In the state of CA, once a gun is made into a rifle, it is always a rifle. Building a pistol using a rifle lower means, in the eyes of the CA DOJ, that you’re just building an illegal rifle – an SBR. That’s bad.

80% Lower Fire/Safe Marked (1-pack)

Lucky for you, an 80% lower is not considered a rifle! You get to legally make it a pistol lower just by machining it – just don’t ever install any rifle parts on it, like a buttstock.

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  1. Don’t keep parts around that could be used to make an SBR.

The ATF likes to throw around the word “intent” quite a lot, especially when talking about building guns. If you have a bunch of pistol parts laying around and an empty rifle lower receiver, you could be viewed as having the “intent” of building an SBR. That’s a huge no-no.

  1. You must build your AR pistol as a single-shot weapon.

This is where a ton of legal mud gets thrown around. California has what’s called the “Unsafe Handgun” law. Without getting into nitty-gritty details, this law carries a ton of red tape and dangerous legal boobytraps for you, the AR pistol builder.

Fear not! There’s a very easy way to get exempt from the Unsafe Handgun law by building your AR pistol as a single-shot weapon. To do this, you’ll need a barrel length of at least 6 inches (we recommend a 7″ AR pistol upper just to be safe) and a device called a “sled”. The sled is just a solid block of metal that sits in place of your AR’s magazine, effectively restricting the weapon to be “breech-loaded” and thus single-shot only.

Once you’ve finished your build, you can switch out that sled for a 10-round magazine, as long as its fixed.

  1. Keep documentation that you built your AR pistol as a single-shot weapon!

This is very important. It’s perfectly legal to convert your newly built “single-shot” AR pistol into a semiautomatic – but if you’re ever questioned by authorities about the history of your AR pistol, you’ll need to keep proof that it was, at one point, a single-shot weapon during production. Silly, right? Again, there’s crazy legislation covering this and it makes no sense, but that’s what it takes to legally build an AR pistol in CA. There’s an easy way to satisfy this proof: Document every step of your build with pictures.

You can even post the progress of your build on your favorite gun forum for all to see, though we strongly recommend taking pictures of your build (be sure to show the sled installed!) and keeping them safe on a thumb drive or even printing them.

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  1. Build your AR pistol with a fixed magazine!

This is perhaps the most important part of your AR pistol build: Your magazine has to be fixed. It cannot be made detachable, and bullet button laws no longer apply – they, too, constitute a detachable magazine as of January 1, 2017.

As long as your AR pistol does not meet the definition of an assault weapon (by having something like the AR MagLock installed), you’re good to go! If you didn’t buy your lower parts kit yet, you can pick up our combo kit. This is a CA-compliant lower parts kit that includes the ARMagLock!

ARMagLock - AR-15 Magazine Lock

Bullet Buttons no longer count for the “fixed magazine” requirement. The ARMagLock will be a key part of legally building your AR pistol in CA.

  1. Serialize your 80% lower!

Effective July 1, 2018, all home-built firearms made in the state of California will require a serial number and other specific markings in order to remain legal. The bill, AB857, will also require your finish your AR build before this deadline, otherwise, you’ll have to register your weapon with the CA DOJ.

Here are the requirements for marking your lower:

  • Markings must be at least .003” deep and printed no smaller than 1/16”
  • Markings must use Roman letters and Arabic numerals
  • Markings must include a serial #, model, caliber, maker’s name (that’s you!), city, and state

Starting January 1st, 2019, it will be illegal to possess a home-built firearm in CA without the identifying information engraved onto its receiver. 

Bullet Buttons don’t qualify as a “fixed magazine” solution anymore. Luckily, there’s the ARMagLock, which does. This will be a critical component of your CA-compliant pistol build. 

  1. Don’t install of the following on your AR pistol:

Installing any of these devices on your AR pistol will make it an SBR or an otherwise illegal weapon:

  • Stock of any kind
  • Braces of any kind (though not technically illegal, these are a gray area in CA)
  • Detachable magazine (bullet buttons don’t count!)
  • Forward pistol grip of any kind
  • Magazine with a capacity greater than 10 rounds
  • Suppressor or noise-reduction device of any kind

*DISCLAIMER: CA’s gun laws – especially those concerning AR 15s and AR pistols – are immensely complex. This article does not, in any way, constitute legal advice, nor should it be construed as legal guidance. If you’re uncertain about whether you’re following the right steps to legally build an own an AR pistol in CA, speak a lawyer who’s well-versed in firearms laws.

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