Putting a vertical foregrip on an AR pistol is legal under federal law only if the firearm’s overall length is 26 inches or more. Below that length, attaching a vertical foregrip turns the pistol into an “any other weapon” (AOW) under the National Firearms Act, and you must register it with the ATF before making the modification. Skipping registration is a federal felony carrying up to 10 years in prison.
Why the Foregrip Matters
A pistol is defined by federal law as a firearm designed to be held and fired with one hand. The ATF has long taken the position that bolting a vertical grip onto a handgun means it is no longer designed for one-handed use.1Bureau of Alcohol, Tobacco, Firearms and Explosives. Adding a Vertical Fore Grip to a Handgun Once the firearm loses its pistol identity, it can fall into the NFA’s “any other weapon” category, which covers concealable firearms that don’t fit the pistol, rifle, or shotgun definitions.2Office of the Law Revision Counsel. 26 USC 5845: Definitions
The concealability piece of the AOW definition is what makes overall length the deciding factor. A firearm 26 inches or longer isn’t considered concealable on the person, so it cannot be an AOW no matter what grip is on it.3ATF. NFA Handbook – Chapter 2: What Are Firearms Under the NFA It also isn’t a rifle, because it has no shoulder stock. The result is a plain “firearm” under federal law, outside NFA registration.
How to Measure Overall Length
The measurement decides the case, so it has to be done the ATF’s way. Overall length runs along a line parallel to the bore, from the rearmost point of the firearm to the tip of the muzzle or a permanently attached muzzle device.3ATF. NFA Handbook – Chapter 2: What Are Firearms Under the NFA A few specifics catch people out.
A muzzle device only counts toward length if it’s permanently attached. Permanent attachment means full-fusion welding, high-temperature silver soldering at 1,100°F or above, or a blind pin with the head welded over. A thread-on flash hider or brake you can spin off with a wrench does not count. If the receiver extension or buffer tube folds or collapses, the ATF measures with it in its shortest configuration. Stabilizing braces and buffer tubes themselves do count, measured to their rearmost fixed point.
If your build is anywhere near the 26-inch line, measure it fully collapsed and count only the muzzle devices you’ve actually pinned and welded. A quarter-inch short is enough to turn a legal AR pistol into an unregistered NFA weapon.p>
Angled Foregrips and Handstops
Not every forward accessory triggers reclassification. The ATF’s concern is specifically the vertical grip, because a perpendicular grip is what signals two-handed use.
Angled foregrips, which slope forward rather than hanging straight down, have not been treated as changing a pistol’s one-handed design. Adding an angled foregrip to an AR pistol does not reclassify it as an AOW, regardless of overall length. The same generally holds for handstops and barricade stops, which are small protrusions that keep your hand from sliding toward the muzzle without providing a full gripping surface.
The ATF has never published a precise angle that separates “vertical” from “angled.” A grip marketed as angled but hanging nearly straight down sits in ambiguous territory. Products with a longer track record of acceptance, like the Magpul AFG, are the safer choice when you want to stay clearly on the legal side.
If Your AR Pistol Is Under 26 Inches
You have two options: keep the pistol as-is with an angled grip or handstop, or register it as an AOW before installing a vertical foregrip. There is no after-the-fact registration.
Registration means filing ATF Form 1, Application to Make and Register a Firearm, and waiting for approval before touching the gun.4Bureau of Alcohol, Tobacco, Firearms and Explosives. NFA Handbook – Chapter 6: Making NFA Firearms by Nonlicensee You submit fingerprints and photographs with the application.5Bureau of Alcohol, Tobacco, Firearms and Explosives. Application to Make and Register NFA Firearm – ATF Form 5320.1
One recent change helps: as of January 1, 2026, the NFA making tax for AOWs, SBRs, short-barreled shotguns, and silencers dropped from $200 to $0. Only machineguns and destructive devices still carry the $200 tax.6Office of the Law Revision Counsel. 26 USC 5811: Transfer Tax The registration itself is unchanged; only the fee went away.
As of February 2026, Form 1 processing averages about 36 days through the ATF’s eForms system and 20 days on paper.7Bureau of Alcohol, Tobacco, Firearms and Explosives. Current Processing Times Individual applications can run longer if they need additional review.
Penalties and Constructive Possession
Making an unregistered AOW by attaching a vertical foregrip without approved paperwork carries a fine of up to $10,000, up to 10 years in federal prison, or both.8GovInfo. 26 USC 5871: Penalties The firearm is also subject to seizure and forfeiture.5Bureau of Alcohol, Tobacco, Firearms and Explosives. Application to Make and Register NFA Firearm – ATF Form 5320.1 The government does not have to prove you knew the modification was illegal.
You don’t always have to attach the grip to face risk. Under constructive possession, prosecutors can argue that owning both a sub-26-inch AR pistol and a vertical foregrip amounts to possessing the parts to make an unregistered NFA weapon. ATF enforcement of that theory in this context is uncommon when the parts sit unassembled, but the exposure exists, especially if the foregrip has no other lawful firearm it could go on. Owning the same foregrip alongside a legal rifle or a pistol over 26 inches removes the issue, because neither combination produces an NFA weapon.
State Law Can Add Restrictions
Federal law is the floor. Some states restrict AR-platform pistols or regulate foregrips independently of the federal classification, and local jurisdictions can layer on more. Verify the rules where you live, where you shoot, and anywhere you plan to transport the firearm before installing anything.