NFA, Constructive Possession, and How to Stay Out of Jail

DISCLAIMER: We do not offer legal advice and nothing contained herein should be interpreted as legal advice. The legality of possession of any firearm is dependent on you and the state in which you reside. You are responsible for you, so understand the law before you venture into unfamiliar waters.

Short Story: The laws as they pertain to AR features are extremely important to the DIY-er. Make sure you understand these implications before you assemble an AR. If your build qualifies as an SBR or AOW be cautious. And be sure to follow the ATF process or you risk going to jail.

Current Law: NFA

Categorization of firearms under federal regulation was originally made in the National Firearms Act of 1934 (the NFA). NFA Title I covers your modern rifle, shotgun, and pistol. NFA Title II covers more sinister contraptions, like machine guns, short-barreled rifles and shotguns, suppressors/silencers, destructive devices, and “any other weapon” otherwise unclassified.

We won’t consider shotguns (Title I or Title II), because ARs are not shotguns.

Rifle

The legal definition of “Rifle” is a firearm with a buttstock that is intended to be fired from the shoulder, has a rifled barrel at least 16″ in length (including any permanently attached muzzle device), and has an overall length of at least 26″.

Pistol

A “Pistol” is a firearm designed to be operated using one hand (even though most civilized people equipped with two hands use ’em both).  If a firearm lacks a buttstock (and therefore, is not designed to be fired from the shoulder), it is probably considered a pistol (unless you install a vertical foregrip, in which case it is classified as Any Other Weapon [AOW], an NFA Title II weapon).

Short-Barreled Rifle (SBR)

Any firearm that has a buttstock installed and has either a rifled barrel under 16″ (including any permanently attached muzzle device) or an overall length under 26″, it is considered a “Short-Barreled Rifle” (SBR; an NFA Title II weapon).

Machine Gun

Any firearm that has a mechanism that results in more than one round being fired by pulling the trigger to the rear once is considered a “Machine Gun” or fully-automatic weapon. For the average citizen, a machine gun must be transferable, per federal definitions. You may not manufacture a machine gun, unless you are a Type 07 FFL and are registered as Class 2 SOT, and even then, you may only manufacture machine guns for government agency sales. We will not discuss machine guns further in this article.

Sound Suppressor (a.k.a. “Silencer”)

A “Sound Suppressor” is any device attached to the muzzle of a firearm that is designed to reduce the audible signature of that firearm. Suppressors may be purchased as suppressors, or may be manufactured from a variety of readily available components. While we believe that a sound suppressor is a great accessory for the AR, it is not part of the firearm, itself. As such, we will not discuss sound suppressors further in this article.

Destructive Device

“Destructive Devices” include explosive devices and rifled firearms with a bore over 1/2″ or .50 caliber. Neither of these pertain to the construction of an AR, so we will not discuss these further in this article.

Any Other Weapon (AOW)

“Any Other Weapon” is basically a junk drawer classification for any firearm or associated device that cannot be classified as a Title I firearm and does not fit into any other category of Title II items.

Title I versus Title II

Title I firearms (rifles, shotguns, pistols/handguns) are readily transferrable with relative ease. Generally, they may be manufactured by anyone otherwise permitted to posses a firearm for personal use without any registration or background check, or they may be purchased with a simple background check. Note that if you are not a Type 07 FFL, you MAY NOT manufacture a firearm with the intent to sell it.

Manufacture, purchase, or possession of Title II firearms and devices (machine guns, short barreled rifles/shotguns, sound suppressors, destructive devices, and any other weapon) is less straightforward. These devices require additional notification, registration, and permitting at the federal and local levels. Please visit our NFA Guidance article for more information on the NFA and associated processes.

NFA Considerations for the AR

NFA classifications that apply to DIY ARs are primarily Short Barreled Rifle and Any Other Weapon. Because both classifications, as they are applied to ARs, are dependent on the classification of the firearm as a rifle or pistol, this is the first step in dissecting these pitfalls. First we will explore the effects of the overall length and barrel length on classification. Then we will explore the implications of what you have attached to the gun.

Lengths

Default Classification Based on OAL and Barrel Length

Overall Length (OAL)

Overall length is measured from the rear of the buttstock (or receiver extension, if a pistol) to the tip of the barrel with any removable muzzle device removed.  If the firearm is equipped with an adjustable buttstock, the measurement is taken with the buttstock fully extended.  If a muzzle device is permanently attached (i.e. pinned and welded), the measurement is made to the tip of the muzzle device.

Barrel Length

If an ATF agent shows up at the range and you are out there with a firearm that is questionable, they will measure the length of your barrel very simply: by running a rod down the bore of the barrel and measuring the distance between the bolt face and the farthest fixed point of the barrel.

If you want to see how your firearm measures up, get yourself a long rod that will fit down the bore of your firearm.  You can use a cleaning rod or go to Lowe’s or Home Depot and buy a 0.1875″ (for 5.56) or 0.25″ (for 7.62) wooden dowel.

• With the bolt closed, run a rod/dowel down the bore of the barrel as far as it will go. It should be touching the face of the closed bolt.
• With the rod fully inserted, mark it where it emerges from the crown of the barrel. It is best to remove any removable muzzle device for this.  If you have a permanently attached muzzle device, you can mark where the rod/dowel exits the muzzle device, as this is the legal “end” of your barrel.
• Measure the rod/dowel from the end that was touching the bolt face to the mark you just made.

Attachments

Title I vs. Title II

Buttstocks

This one is relatively simple.

If you put a buttstock on a pistol, it is no longer designed to be fired with one hand. Therefore, is no longer a pistol. NFA classifies any firearm with 1) has a rifled barrel, 2) does not meet qualify as a rifle by both OAL and barrel length, and 3) is outfitted with a buttstock, as a short-barreled rifle (a Title II weapon).

Pistol Braces

This one is a little less simple.

A pistol brace is a device that can be installed on a pistol (especially an AR-style pistol) to allow a shooter to more easily wield a heavy weapon with one hand. This device was designed to allow disabled shooters, who would not otherwise be able, to handle an AR (or similar) pistol.

While some pistol braces look very similar to buttstocks, and it is very natural to shoulder a pistol outfitted with a pistol brace, the ATF generally accepted the use of this accessory for a long time.

In 2022, the ATF set policy in motion that would render any pistol brace installed on a pistol a short-barreled rifle and, if not registered as an NFA Title II firearm, illegal. In 2023, this ruling went into law.

After a public shitstorm-fueled Supreme Court ruling, the ATF has clarified that, since they do not regulate firearms accessories, the classification of a pistol equipped with a stabilizing brace as an NFA Title II firearm only applies if the pistol brace is installed by the firearm manufacturer.

For the time-being, if you install a pistol brace on an AR pistol, you are not breaking the law.

Vertical Foregrips, Angled Foregrips, Hand Stops, Finger Stops, and Barricade Stops

So far, things seem somewhat straightforward. The waters get muddy from hereon-out.

If you own an AR pistol, you MAY NOT affix a vertical foregrip (VFG) to the area forward of the pistol grip, without first registering the AR as an AOW. Pistols are defined as being designed to fire with one hand (even if you routinely use two). When you put a VFG on it, it magically transforms into a pistol designed to fire with two hands. Any. Other. Weapon.

Pistol Upper + AFG or Hand Stop or Finger Stop or Barricade Stop ≠ Prison

But don’t confuse a vertical foregrip for any other device attached to the fore-end of your pistol.

An angled foregrip (AFG) is one that is installed forward of the pistol grip. But doesn’t protrude straight down like a VFG. One would think that this wouldn’t matter, given the definition of a pistol and the transformation that occurs with a VFG. However, the ATF has determined that AFGs are not vertical foregrips, and therefore, do not convert a pistol into an AOW.

Hand stops and finger stops are designed to keep your hand from accidentally slipping off of the handguard and into the path of a bullet. Now, these are vertical protrusions from the fore-end of your pistol…but they aren’t long enough to be considered foregrips. Therefore, installing a hand stop or finger stop does not convert a pistol into an AOW.

Barricade stops are vicious toothed creatures that are designed to jam into wooden barricades for additional support. You probably wouldn’t want to wrap your fingers around one of these. But even if you did, its not considered a VFG, so it does not convert your pistol into an AOW.

We know this is confusing and doesn’t quite follow sound logic. We are not arguing with this week’s opinion (which excludes AFGs, hand stops, finger stops, and barricade stops from the Title II features list), but you should be aware that opinions can and do change. Most of the time, opinions change because of gun owner behavior…so be responsible. Thankfully, if the ATF reverses its opinion on AFGs, hand stops, finger stops, and/or barricade stops, they are easy enough to remove and cheap enough that it probably won’t get your panties in too much of a wad.

NFA: How to Stay Legal

If you are building an AR, you have a few options:

1. Install a barrel that is nominally at least 16″ long. It isn’t a bad idea to confirm that the barrel length measures at least 16″ per the procedure above.
2. If you want to minimize the length of your AR rifle, you can install a shorter barrel if you 1) permanently attach the muzzle device (pin and weld), and 2) the combined installed length of the barrel and muzzle device meet the minimum 16″ requirement (be sure to factor the overlap of threads).
3. If you intend to build an AR with a barrel that is less than 16″ (including permanently attached muzzle device), you can build it as a pistol without any further federal consideration (be aware of state and local laws).
   • If your AR has a barrel under 16″ (including any permanently attached muzzle device), DO NOT PUT A BUTTSTOCK ON IT, at least until you register it as an NFA SBR.
   • If your AR is built as a pistol (i.e. no buttstock + barrel under 16″), DO NOT PUT A VERTICAL FOREGRIP ON IT, at least until you register it as an NFA AOW.

“Constructive Possession” and How It Can Screw You

“Constructive Possession” is a dangerous term for someone who likes to build ARs. In essence, as it applies to your collection of ARs and parts, it means “you have the ability to do something even if you haven’t” and “because you have the ability to do something, you have broken the law”.

Excuse me???

Let’s walk through a couple of examples.

Example 1: The Parts Are the Whole

Let’s say you have a loose pistol upper receiver sitting in one room of your house. Let’s say you have a loose carbine lower receiver in another. In the eyes of the law, you can be found guilty of intent to assemble an NFA Title II weapon (or “constructive possession”). Even if you have never slapped that pistol upper on that carbine lower. Even if the thought to do so has never crossed your mind. You could, and that’s enough. And given that the pistol upper is floating around the house without its pistol lower mate (i.e. it is not part of an assembled pistol), you are, therefore, even more likely to build an SBR. Pre-crime. Go to jail. Do not pass go. Do not collect $200.

Example 2: The Boy Scout

Let’s say that you’ve decided that you don’t want to deal with the pistol brace drama and have disposed of a pistol brace that was previously installed on an AR pistol. Now you have your brace-less pistol outfitted with a carbine receiver extension sitting in your gun safe. Let’s say you are also building another AR; a carbine (classified by NFA as a rifle) this time. Right next to that gun safe, you have your brand new Magpul CTR buttstock for your new build. “Constructive Possession” to the rescue. Because you still have that naked carbine receiver extension on your AR pistol searching for a buttstock, and because you have a loose buttstock that is compatible with that carbine receiver extension, you have the partially cooked ingredients to make an NFA Title II weapon without the appropriate tax stamp, and therefore, you can be found guilty of a felony. No sh!t.

What To Do If You Are in a “Constructive Possession” or Other Illegal Situation

First, don’t tell us! We don’t care and we don’t want to know. We also recommend that you don’t tell anyone else and move to the next step.

Second, stop bending or breaking the law. Remedy the situation before you end up in prison.

If you have a vertical foregrip attached to your pistol, remove it. We understand the benefits of a foregrip on an AR pistol. If you are concerned about blowing your fingers off or the ergonomics of an AR pistol, feel free to swap it out for an angled foregrip, hand stop, finger stop, or barricade stop, none of which currently make your AR pistol any more dangerous.

If you have an AR pistol built with a carbine or rifle receiver extension (a.k.a. buffer tube), but do not have a buttstock or pistol brace attached (i.e. a bare buffer tube), you are wading into muddy waters. Technically speaking, if you don’t have a buttstock (or pistol brace) attached to the firearm, the firearm itself is not in violation.  However, as described in the scenario above, if you have a buttstock compatible with that carbine/rifle receiver extension lying around, you could have a problem. And it doesn’t matter if you simply followed the ATF’s guidance in May 2023 by removing your pistol brace; saying “but, you told me to” or “but, I didn’t know” is not a defense for breaking the law, and breaking one law to follow another is still…gasp…breaking the law.

Pistol Upper + Pistol Lower ≠ Prison

If you have a pistol upper, keep it installed on a dedicated pistol lower.  That means a lower equipped with a pistol buffer tube or (for the time-being) a carbine buffer tube and a pistol brace. As ridiculous as it sounds to anyone who knows their way around an AR, having the pistol upper installed onto a pistol lower takes some of the perceived intent out of the question (you have to put forth twice as much effort to break the law, even if it takes 10 seconds instead of 5). This doesn’t mean that you will be absolved of “constructive possession” for this or any other potential violation. But you will have an easier time explaining yourself.

Pistol Upper + Carbine/Rifle Lower = Prison

Now, if you have a pistol upper, a carbine lower (with buttstock), and no pistol lower, you have a bit of a problem. There is no acceptable explanation for having a pistol upper, a carbine lower, and no pistol lower in sight, other than an intent to assemble an SBR. If you have not registered a lower receiver as an SBR, you are guilty of “constructive possession”. Don’t panic if you had no idea, BUT TAKE IMMEDIATE ACTION. You have options.

If you really want an SBR, begin the process to register the lower receiver as an SBR and do one of the following immediately. You cannot legally build or possess an SBR before you receive your tax stamp so undo it now!).

Option 1: Make it a Pistol

Convert the carbine/rifle lower into a pistol lower, if legally permitted¹. If acceptable to convert the carbine/rifle lower into a pistol lower¹, you may either remove the buttstock (and get it out of the house) or better yet, replace the carbine/rifle receiver extension with a pistol receiver extension. If you have to wait for a pistol receiver extension, at least remove the buttstock and get it out of the house.

1: Note that if your receiver was manufactured as an assembled carbine or rifle, you cannot legally convert it to a pistol. If your receiver was purchased as a stripped or assembled receiver (and not part of a complete firearm) or as an assembled pistol, you can build it into whatever you want. Put simply: pistols can become carbines/rifles; carbines/rifles cannot become pistols. However, even if you are allowed to convert the “accidental SBR” into a pistol, you MUST ALSO FOLLOW YOUR STATE AND LOCAL LAWS. Your state and/or municipality may have requirements for construction, purchase, or possession of pistols. Just because you aren’t heading to a federal prison doesn’t mean you won’t be heading to prison…

Option 2: Make it a Carbine or Rifle

Convert the pistol upper into a carbine/rifle upper. You can swap the pistol-length barrel out for a longer barrel that meets the criteria for a rifle barrel (i.e. at least 16″ long) and be out of troubled waters (please check our Handguard Length article, for additional considerations). If you cannot do this immediately (e.g. you have to wait to receive a longer barrel), at least remove the pistol-length barrel immediately. If you cannot do this immediately (e.g. you don’t have the barrel nut wrench needed to remove the pistol barrel), we recommend that you immediately 1) remove the carbine buttstock and get it (and any other loose buttstocks) out of the house, or 2) separate the receivers and remove the pistol upper from the same house as the carbine lower (and any other non-pistol lowers) until you can remove the pistol-length barrel, to prevent any perception of intent.

Option 3: Build a New Pistol Lower

Build a pistol lower to put your pistol upper onto (e.g. if you can’t legally convert the carbine/rifle lower into a pistol lower¹). If you cannot do this immediately (e.g. you have to wait for a permit, a new lower receiver, or parts), we recommend that you immediately either 1) remove the carbine buttstock and get it (and any other loose buttstocks) out of the house, or 2) separate the receivers and remove the pistol upper from the same house as the carbine lower (and any other non-pistol lower) until you have a pistol lower in hand, to prevent any perception of intent.

Tell Us What You Think!

Please enable JavaScript in your browser to complete this form.

Was This Page Helpful? *

• Extremely
• Very
• Somewhat
• Meh
• Definitely Not

How Can We Make It Better?

Send It