Firearms & 2A Legal Glossary (2026): NFA, Carry & Gun-Law Terms
Quick answer: This glossary defines the firearms, ammunition, and Second Amendment legal terms every gun owner runs into, updated for 2026 law. The biggest recent change: on January 1, 2026 the federal NFA tax stamp for suppressors, short-barreled rifles, short-barreled shotguns, and AOWs dropped from 200 dollars to 0 dollars under H.R.1 (signed July 4, 2025). You still file a Form 4 or Form 1 and pass a background check, but no longer pay the tax.
2026 at a glance
0 dollarsNFA tax stamp 2026
29Permitless-carry states
42States suppressors legal
50+Terms defined
Firearms & gun-law glossary
Type in the box to filter, or click Term or Category to sort. Every definition is written in plain language for quick reference.
| Term | Category | Definition |
|---|---|---|
| National Firearms Act (NFA) | Federal Law | The 1934 law regulating suppressors, short-barreled rifles and shotguns, machine guns, AOWs, and destructive devices; requires ATF registration and a background check. |
| Gun Control Act (GCA) | Federal Law | The 1968 law that created the Federal Firearms License system, defined prohibited persons, and set rules for interstate firearm sales. |
| Firearm Owners Protection Act (FOPA) | Federal Law | A 1986 law adding safe-passage travel protections for gun owners and containing the Hughes Amendment. |
| Hughes Amendment | Federal Law | The 1986 FOPA provision that closed the machine-gun registry to new civilian machine guns, freezing legal civilian ownership to those registered before May 19, 1986. |
| Form 1 | ATF Process | The ATF application to MAKE an NFA item yourself, such as building a short-barreled rifle from a standard rifle. |
| Form 4 | ATF Process | The ATF application to TRANSFER an NFA item to you from a dealer or another individual. |
| Form 4473 | ATF Process | The ATF firearms transaction record a buyer completes at the point of sale for any dealer purchase. |
| Tax Stamp | ATF Process | The NFA making or transfer tax. As of January 1, 2026 it is 0 dollars for suppressors, SBRs, SBSs, and AOWs (previously 200 dollars); machine-gun transfers still cost 200 dollars. |
| eForms | ATF Process | The ATF online system for electronically filing NFA applications such as Form 1 and Form 4. |
| SOT (Special Occupational Taxpayer) | ATF Process | A Federal Firearms Licensee that pays a special tax to manufacture or deal in NFA items. |
| NFA Trust / Gun Trust | ATF Process | A legal entity used to own NFA items, allowing multiple approved users and simplified estate transfer. |
| NICS | Regulatory Body | The FBI National Instant Criminal Background Check System used to screen firearm buyers. |
| ATF | Regulatory Body | The Bureau of Alcohol, Tobacco, Firearms and Explosives, which enforces the NFA and Gun Control Act. |
| FFL (Federal Firearms License) | Regulatory Body | The federal license required to engage in the business of manufacturing or dealing firearms. |
| Suppressor / Silencer | NFA Item | A muzzle device that reduces the sound of a gunshot; NFA-regulated and legal for civilians to own in 42 states. |
| SBR (Short-Barreled Rifle) | NFA Item | A rifle with a barrel under 16 inches or an overall length under 26 inches; NFA-regulated. |
| SBS (Short-Barreled Shotgun) | NFA Item | A shotgun with a barrel under 18 inches or an overall length under 26 inches; NFA-regulated. |
| AOW (Any Other Weapon) | NFA Item | An NFA catch-all for concealable or disguised firearms such as pen guns, cane guns, and smooth-bore pistols; transfer tax dropped to 0 dollars in 2026 (previously 5 dollars). |
| Destructive Device (DD) | NFA Item | An NFA category covering explosives, grenades, and firearms with a bore over one-half inch, with limited sporting exceptions. |
| Machine Gun | NFA Item | A firearm that fires more than one round with a single trigger pull; civilian ownership is limited to examples registered before May 19, 1986. |
| Constitutional / Permitless Carry | Carry Law | Carrying a concealed handgun without a permit, legal in 29 states as of 2026. |
| Concealed Carry (CCW) | Carry Law | Carrying a hidden handgun; requires a license in states that are not permitless-carry. |
| Open Carry | Carry Law | Carrying a visible firearm; its legality and restrictions vary widely by state. |
| Shall-Issue | Carry Law | A jurisdiction that must issue a carry permit to any applicant who meets the objective requirements. |
| May-Issue | Carry Law | A jurisdiction that historically had discretion to deny permits; largely curtailed after the 2022 Bruen decision. |
| Reciprocity | Carry Law | One state recognizing a carry permit issued by another state. |
| Red Flag Law / ERPO | Carry Law | An Extreme Risk Protection Order that allows a court to temporarily remove firearms from a person deemed a risk. |
| Castle Doctrine | Carry Law | A legal principle allowing the use of force to defend one’s home without a duty to retreat. |
| Stand Your Ground | Carry Law | A principle removing the duty to retreat before using lawful force in self-defense in public. |
| Prohibited Person | Legal Status | Someone barred by law from possessing firearms, such as a convicted felon or a person convicted of domestic violence. |
| Straw Purchase | Legal Status | Illegally buying a firearm on behalf of someone who cannot legally purchase one; a federal felony. |
| Constructive Possession | Legal Status | Possessing the parts or means to assemble a regulated configuration, which can itself be unlawful. |
| AR-15 | Firearm Type | A modular semi-automatic rifle platform; the name means ArmaLite Rifle, not ‘assault rifle’. |
| Assault Rifle | Firearm Type | A select-fire military rifle capable of automatic or burst fire; heavily NFA-restricted for civilians. |
| Assault Weapon | Firearm Type | A feature-based legal and political classification that varies by state; distinct from a true ‘assault rifle’. |
| Semi-Automatic | Firearm Type | A firearm that fires one round per trigger pull and automatically loads the next. |
| Bullpup | Firearm Type | A rifle design with the action placed behind the trigger for a shorter overall length. |
| Pistol Brace | Component | A stabilizing brace for large-format pistols whose regulatory status has been repeatedly contested in court. |
| Lower Receiver | Component | The serialized, legally controlled part of an AR-type firearm, which is the ‘firearm’ itself under federal law. |
| 80 Percent Lower | Component | An unfinished receiver not yet legally a firearm; the 2022 ATF frame-and-receiver rule tightened how these are treated. |
| Magazine | Component | An ammunition-feeding device; capacity limits apply in some states. |
| Threaded Barrel | Component | A barrel machined to accept a suppressor or muzzle device; restricted in some states. |
| Caliber | Ammunition | The diameter of a firearm’s bore and its bullet, such as 9mm or .223. |
| Grain (gr) | Ammunition | A unit of bullet or powder weight equal to one seven-thousandth of a pound. |
| Hollow Point (JHP) | Ammunition | An expanding bullet designed for self-defense. |
| Full Metal Jacket (FMJ) | Ammunition | A jacketed, non-expanding bullet commonly used for target practice. |
| Plus-P (+P) | Ammunition | Ammunition loaded to a higher-than-standard pressure for increased velocity. |
| Subsonic | Ammunition | Ammunition traveling below the speed of sound, roughly 1,125 feet per second, ideal for suppressed shooting. |
| D.C. v. Heller (2008) | Court Case | The Supreme Court decision affirming an individual right to keep a handgun in the home for self-defense. |
| McDonald v. Chicago (2010) | Court Case | The decision applying the Second Amendment to state and local governments. |
| NYSRPA v. Bruen (2022) | Court Case | The decision establishing the text-and-history test and striking down discretionary ‘may-issue’ permit regimes. |
Frequently asked gun-law questions
How much is a suppressor tax stamp in 2026?
As of January 1, 2026 the federal transfer tax on a suppressor is 0 dollars, down from 200 dollars, under H.R.1. You still submit an ATF Form 4, pass a background check, and provide fingerprints, but there is no longer a tax to pay.
What barrel length makes a rifle an SBR?
A rifle becomes a short-barreled rifle, and therefore NFA-regulated, when its barrel is under 16 inches or its overall length is under 26 inches.
How many states have constitutional (permitless) carry?
29 states allow permitless concealed carry as of 2026. The rest require a concealed-carry license.
In how many states can civilians own a suppressor?
Suppressors are legal for civilians in 42 states with proper NFA registration. They are banned in California, Delaware, Hawaii, Illinois, Massachusetts, New York, New Jersey, and Rhode Island, plus the District of Columbia.
What is the difference between an assault rifle and an assault weapon?
An assault rifle is a select-fire military weapon capable of automatic fire and is heavily NFA-restricted. An assault weapon is a feature-based legal category defined differently by each state that bans them; most so-labeled rifles are ordinary semi-automatics.
Can civilians own machine guns?
Only machine guns registered before May 19, 1986 may be transferred to civilians, due to the Hughes Amendment. That fixed supply makes them very expensive.
What is the difference between an ATF Form 1 and Form 4?
A Form 1 is used to make or build an NFA item yourself, such as turning a rifle into an SBR. A Form 4 is used to transfer an already-made NFA item to you from a dealer or individual.
This glossary is provided for general education and is not legal advice. Firearm laws change and vary by state and locality; always verify current federal, state, and local law or consult an attorney before acting.