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How to Legally Build a Short Barreled Rifle

The latest fad in gun ownership (thanks largely to the ATF’s surprising stance on certain AR accessories) is building and owning NFA gun, especially Short Barreled Rifles, or SBRs. Short Barreled Rifles are a lot like AR 15 pistols, though pistols don’t get that expensive NFA designation. The kicker is the addition of a buttstock. An SBR is defined as a rifle with a barrel shorter than 16 inches, whose maker intended it to be fired from the shoulder. SBRs are superbly popular with elite Special Operations units and SWAT teams for their balance of power, accuracy, and maneuverability. 

Unfortunately for everyone who isn’t a cop or Frogman, like you and us, SBRs are restricted under the National Firearms Act. Because the strict legal requirements make owning an SBR a pain in the ass, we decided to make it a little easier. Below is a high-level summary that’ll help you figure out how to get your hands on one (legally). It’s up to you to seek official legal advice regarding the NFA and your state’s own laws governing the sale and ownership of SBRs. 

The Legal Requirements of Owning an SBR

Before you take any steps in turning an AR 15 pistol into a short barreled rifle you need to start the legal process. The first requirement is filling out ATF Form 1. This form is your application to make or register a firearm. Form 1 is pretty simple to fill out. Most of the information is self-explanatory. You’ll fill out this form and make three copies. Two will be sent to the ATF, and one will be mailed to the Chief Law Enforcement Officer (CLEO) in your city or county. You no longer need to seek permission from your CLEO, you merely have to notify him or her via the Form 1.

What it Costs to Own One

The forms sent to the ATF will need to be sent with appropriate payment. That’ll run you a cool $200 and it can be paid by check, money order, or credit card. After this is all submitted you have to play the waiting game – roughly three to six months. This is where we plug our own recommendation: It’s great to fill that free time with building your own AR 15 pistol that you’ll eventually turn into your SBR. 

AR-15 Pistol Kit (5.56 Caliber, 7" Barrel & 6" Keymod Hand Guard) w/ 80% Lower Receiver

Why bother with this build process? Simple, you’ll proudly own an almost-SBR that you’ve built and can enjoy! You can shoot it, train with it, and configure it to your liking as you wait for your NFA stamp. The best part? The NFA says you can shoulder a pistol brace or stabilizer, effectively making your pistol the next best thing to an outright SBR. 

An SBR That Starts as an AR 15 Pistol 

One step that blurs between the build requirements and legal requirements of an SBR is the marking requirement. This is one of the major reasons an 80 lower is best for building an SBR. It’s unmarked and you can add your own serial numbers easily. The serial numbers and information that must be added need to be .003” deep, and no smaller than 1/16th of an inch. An electro-pencil works well for this. 

Serializing Your Future Short Barreled Rifle

Serializing it is the first step we’d take in finishing an 80 lower. Until you’ve machined it, an 80 lower isn’t legally considered a firearm. This makes it easier to find an engraver to serialize your lower first. You’ll need to have the following information inscribed on your 80 lower: 

  • Name of maker of the gun (That’s you!) 
  • Location (City and state where the firearm was manufactured)
  • Caliber
  • Serial Number (001 works for your first NFA item, or 666 if you’re feeling frisky) 
  • Model Number (If you include a model number on your Form 1 it must also be engraved) 

Build it

After the engraving is finished you can start building your AR 15 pistol and future SBR! You’ll need to mill out your 80 lower receivers with an 80 lower jig, then install a lower parts kit. You’ll also need a pistol buffer tube that cannot accept a buttstock. We start with AR 15 pistols because it’s much cheaper and easier to add a rifle buffer tube and stock to complete your SBR than building a regular AR 15 rifle, then the swapping barrel out for a shorter model.

80% Lower Easy Jig with Tooling

Stamp it, Shoot it!

Once your stamp comes back from the ATF you can legally add a rifle buffer tube and stock, and that’s it! You now have a stable and maneuverable rifle that’s compact and lightweight! SBRs are just downright cool as Hell, and they make excellent self-defense rifles. They’re perfect for home defense, too. With an 80 lower, an AR 15 pistol kit, and a little bit of patience, you can have nearly the same type of rifle used and loved by ODA, Frogmen and Special Operations worldwide – all that’s missing now is a “giggle” switch, but that’s another topic for another day. Stay frosty.


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