Welcome to the Gun Terminology Glossary
Understanding firearms means more than just knowing how to shoot – its about learn the language, culture, and responsibility that comes with the 2nd Amendment. This glossary is designed to provide clear, non-partisan explanations of common terms use in the gun community. Whether you’re new to firearms or a seasoned enthusiast, this resource will help you better understand the words, phrases, and concepts that shape American gun culture.
A
Action
The mechanism that loads, fires and ejects cartridges (e.g., bolt-action, pump-action, semi-automatic).
ACP (Automatic Colt Pistol)
A cartridge designation created by John Browning, used in calibers like .45 ACP
Ammunition
Ammunition refers to projectiles like bullets, shells, and rockets, along with their components such as primers, powder, and casings, designed to be discharged from firearms.
Assault Weapon
The term “Assault Weapon”, coined in the 1980’s in an effort to ban semiautomatic rifles, has arguably become one of the most successful antigun public relations tools in modern history. The term “assault weapon” is now broadly used by antigun activists to describe any and all semiautomatic firearms as taboo and undesirable for private civilian ownership, despite being legally owned and used by millions of Americans. Learn more about this from the National Shooting Sports Foundations Fact Sheet.
AR-15
TThe AR-15 is a lightweight, semi-automatic rifle originally designed by firearms engineer Eugene Stoner for the company ArmaLite. Though it was created for military use, it is now widely sold to civilians for hunting, sport, and self-defense.
About the AR-15
Popularity: Since Colt’s patent expired in the 1970s, many other manufacturers began producing their own versions of the rifle. Today, AR-15–style rifles are among the most popular firearms in the U.S. and the term has become a catch-all for this style of firearm.
“AR” meaning: The “AR” in AR-15 stands for “ArmaLite Rifle,” not “assault rifle” or “automatic rifle”. The 15 refers to the fact that it was the 15th model designed by the company.
Military vs. civilian versions: After ArmaLite sold the design to Colt’s Manufacturing Company in 1959, the rifle was adopted by the U.S. military in 1963 and became the M16. While military versions like the M16 are selective-fire (capable of fully automatic fire), the civilian AR-15 is semi-automatic, firing one round per trigger pull.
Highly customizable: One of the AR-15’s key features is its modular design. Owners can easily customize the rifle with a wide variety of aftermarket accessories, including different barrels, stocks, grips, and optics.
B
Ballistics
The science of projectile motion (internal, external, and terminal).
Barrel
The metal tube through which a bullet travels through when fired.
Bore
The inside diameter of a firearm’s barrel.
Bullet
A bullet is the projectile part of a firearm cartridge that is propelled from the barrel when the firearm is fired. The term is often used incorrectly to refer to the entire cartridge or round of ammunition.
C
Caliber
The science of projectile motion (internal, external, and terminal).
Carbine
The metal tube through which a bullet travels through when fired.
Cartridge
The complete round of ammunition. This includes the case, primer, powder charge and bullet.
Case/Casing
The metal casing (often brass) that holds all the components together in a cartridge.
Centerfire
A cartridge in which the primer is located in the center of the cartridge case head. Unlike rimfire cartridges, the primer is a separate and replaceable component. The centerfire cartridge has replaced the rimfire in all but the smallest cartridge sizes. Except for low-powered .22 and .17-caliber cartridges and a handful of antiques, all modern pistol, rifle, and shotgun ammunition are centerfire.
CHP
Concealed Handgun Permit – Colorado’s legal permit to carry a concealed handgun. Often times referred to as CCW (concealed carry weapon) falsely, as in Colorado the permit is only applicable to handguns not any other form of firearm or defensive tool.
Chamber
the chamber is a cylindrical cavity where a cartridge is inserted and held for firing. This chamber is typically located at the rear of the barrel in rifles, pistols, and shotguns, or within the rotating cylinder in revolvers. It must securely contain the entire cartridge to withstand the tremendous pressures generated during firing.
Key Aspects of a Firearm Chamber:
Chambering: The process of inserting a cartridge into this chamber is called “chambering” or “racking” the round.
Location: In most firearms, the chamber is a cavity at the rear of the barrel. In revolvers, the chambers are individual bores within the cylinder.
Function: The chamber’s primary purpose is to hold the cartridge in the correct position for the firing pin and to contain the resulting explosion.
Pressure Containment: The chamber is a reinforced part of the firearm designed to hold the high-pressure gasses created when the cartridge is discharged.
Single vs. Multiple: Most pistols and rifles have a single chamber in their barrel. Revolvers are known for having multiple chambers, each one capable of holding a single cartridge.
Clip
A term often misused to mean ‘magazine’; technically a clip is a device that holds cartridges together for loading, also known as a stripper clip.
Concealed Carry
Carrying a concealed firearm for personal defense.
D
Decocker
The science of projectile motion (internal, external, and terminal).
Defensive Mindset
The metal tube through which a bullet travels through when fired.
Derringer
A derringer is a small, large-caliber, short-barreled handgun designed to be easily concealable, named after American gunsmith Henry Deringer. These pistols, initially produced by Deringer for personal defense, became popular as pocket pistols, with variations including single-shot or double-barreled designs, some with over/under or side-by-side barrels that pivot for reloading. Modern manufacturers still produce derringer-style firearms in various calibers, though the original design was the single-shot, muzzleloading caplock.
Origin and Naming
- The term “derringer” comes from Henry Deringer, who invented and first produced these pistols in the mid-19th century.
- The name became a generic term for many similar small, pocket-sized handguns due to a widespread typo in newspapers reporting on President Lincoln’s assassination by a Deringer pistol.
Key Characteristics
- Size: Derringers are characterized by their small size, designed for easy concealment.
- Caliber: Despite their small size, they were originally produced in large calibers.
- Barrels: Original derringers were single-barrel, but variations quickly appeared with multiple barrels, such as the over/under Remington double-barrel design or the Sharps four-barrel “pepperbox”.
- Action: Historically, derringers used various actions, from muzzleloading percussion locks to later metallic cartridge designs.
Usage and Modern Production
Modern Derringers: Today, several companies manufacture derringer-style handguns, offering various calibers and modern features for concealed carry.
Purpose: Originally intended as a hold-out or concealed personal protection firearm, they were favored by gamblers and individuals needing discreet protection.
Discharge
means to intentionally or unintentionally cause it to fire, expelling a projectile like a bullet or pellet from the barrel. There are two main categories of discharge: a negligent discharge results from operator error or mishandling, such as a user’s carelessness, and is a preventable, chargeable offense; an accidental discharge is caused by a mechanical or equipment failure, not human error, and is generally not a criminal offense.
When the term “discharge” is used in a legal context, it refers to the act of firing a firearm.
- Unlawful discharge is a criminal act, often a felony, where a firearm is fired illegally, such as into a building, occupied vehicle, or public space, and is subject to severe penalties.
- Criminal negligence can be a key factor in unlawful discharge, where the firearm is discharged due to the operator’s reckless disregard for safety rules, even if the intent wasn’t to cause harm.
Types of Discharge and Their Causes
A gun not designed to be “drop-safe” being dropped
Negligent discharge: Often stems from operator error, such as:
Improper handling of the weapon
Failing to keep the finger off the trigger
Mishandling a loaded firearm
Not following basic firearm safety rules
Accidental discharge: Occurs due to a mechanical issue or equipment failure, including:
A broken firing pin
A stuck firing pin
A malfunction of the firearm
Dry Fire
the practice of activating its firing mechanism without any live ammunition in the chamber. The shooter pulls the trigger, and the hammer or firing pin moves forward with an audible “click,” but no shot is fired.
Dry-firing is a common training method that helps shooters improve their skills without the noise, recoil, or expense of live ammunition.
Purpose of dry-firing
Cost-effective: It allows for extensive practice without paying for expensive ammunition or range fees.
Improves technique: Dry-firing allows a shooter to focus on fundamental skills such as trigger control, sight alignment, and grip without the distractions of a loud bang or recoil.
Builds muscle memory: Frequent, deliberate practice of handling the firearm builds the muscle memory necessary to make consistent and accurate shots.
Practices drills: Advanced maneuvers like drawing from a holster, performing reloads, or clearing simulated malfunctions can be practiced safely at home.
Dummy Round
The metal casing (often brass) that holds all the components together in a cartridge.