Firearm Technology and Vocabulary

To write or speak with legitimacy about guns, gun crime, and gun violence requires accurate use of terminology. This is a basic guide for describing firearm technology, accessories, and safety or regulatory technologies.


Fact: In 2013, handguns were used in 90.7% of firearm homicides where the type of gun used was known.“Crime in the United States (2013).” Federal Bureau of Investigation.

Long Guns

Automatic vs. Semi-Automatic

Automatic: Firearms that continuously fire when the trigger is pulled and stop when the trigger is released or all the ammunition runs out — often referred to as “machine guns.”Opfer, Chris. “What’s the Difference between a Semiautomatic Weapon and a Machine Gun?” How Stuff Works. January 28, 2013. Automatic weapons are regulated under the National Firearms Act, which prohibits civilians from purchasing or possessing automatic weapons manufactured after 1986. To obtain an automatic weapon produced before 1986, a person must complete an ATF application form, obtain law enforcement certification, and pass a background check. Transfers of pre-1986 machine guns also require payment of $200.“The Bureau of Alcohol, Tobacco, Firearms and Explosives’ National Firearms Registration and Transfer Record.” Office of the Inspector General. June 2007. 'The Bureau of Alcohol, Tobacco, Firearms and Explosives’ National Firearms Registration and Transfer Record.” Office of the Inspector General. June 2007.

Semi-Automatic: : Firearms that fire a single shot every time the trigger is pulled and automatically reload without the user having to “cock” the gun or add ammunition. The majority of guns collected and sold in the United States are semi-automatic.“Background Information on So-called “Assault Weapons”” National Shooting Sports Foundation. 2011.

Bullet vs. Cartridge

ChartA cartridge is one piece of ammunition (“ammo”), and a bullet is the part of the cartridge that is propelled. A typical cartridge has four parts:

Bullet: The projectile fired from a cartridge when gases are produced by ignited gunpowder.“Firearms Definitions.” Tennessee Courts.
Case: The container that keeps the parts of the cartridge together. It is often called a “shell casing,” but that is redundant. Police often recover casing at crime scenes.Tompkins, Al. “What Journalists Need to Know about Guns and Gun Control.” Poynter. November 15, 2014.
Gunpowder: The substance that serves as propellant charge.
Primer: An explosive material that initiates the ignition of a cartridge and, when struck, detonates the gunpowder.Ibid. Tennessee Courts.

Additional Ammunition Types

The larger the magazine, the more rounds a shooter can fire before stopping to reload. Currently eight states (CA, CO, CT, HI, MD, MA, NJ, NY) and Washington, DC restrict civilian transfer or possession of high-capacity magazines. Some states define high-capacity magazines as those accepting 10 or more rounds of ammunition, whereas others define them as accepting 15 or more rounds.“Large Capacity Ammunition Magazines Policy Summary.” Law Center to Prevent Gun Violence. May 31, 2013.

Caliber: With the exception of shotguns, firearms are described by their caliber.Luft, Kerry. “Firearms Primer for Journalist.” Medill National Security Zone. Caliber is the measure of the inside diameter of gun’s barrel, and is expressed in millimeters or inches. For a firearm fired from a close distance, the higher the caliber, the more powerful the weapon.Ibid. Topkins, Al

Gauge: A gauge is the measure of how many lead balls of a shotgun bore’s diameter must be combined to weigh one pound. The lower the gauge, the more powerful the weapon.Ibid. Topkins, Al

Assault Weapons

The definition of assault weapon varies among the states that use the term. Federal legislation restricting the possession of these weapons took effect in 1994 and expired in 2004. This legislation defined “assault weapon” to semiautomatic rifles, pistols, and shotguns with at least two of a list of specified military-style features, including flash suppressors, pistol grips, folding stocks, and barrel shrouds. The term also covered a list of named firearms and copies of those named firearms.Violent Crime Control and Law Enforcement Act of 1994, Title XI, Subtitle A.

Today there are seven states (CA, CT, HI, MD, MA, NJ, NY) that restrict access to assault weapons, utilizing varying definitions. Some state apply a “two-feature” test similar to that in the expired federal law, while others employ a broader “single-feature” test. Most definitions include a list of named firearms.Cal. Penal Code § 30510; Conn. Gen. Stat. § 53-202a; H.R.S. § 134-1; Md. Criminal Law Code Ann. § 4-301, Md. Public Safety Code Ann., § 5-101(r)(2); Mass. Gen. Laws ch. 140, §§ 121; N.J. Stat. § 2C:39-1(w); and N.Y. Penal Law § 265.00(22).

Assault weapons are not automatic weapons, which are regulated under the National Firearms Act, as noted above. Assault weapons are sometimes referred to as “assault-style rifles” or “modern sporting rifles.”“Modern Sporting Rifle Facts.” National Shooting Sports Foundation.

Examples of Safety Technologies

Other Terms

Federal Firearms Licensee (FFL): Gun dealers (e.g. gun store owners or pawn shop purveyors), manufacturers, or importers that engage in the business of selling firearm and/or destructive devices and are required to be licensed under federal law.“How to Became a Federal Firearms Licensee (FFL).” Bureau of Alcohol, Tobacco, Firearms, and Explosives. “Application for Federal Firearms License.” Bureau of Alcohol, Tobacco, Firearms, and Explosives. Accessed May 1, 2005. FFLs are required to keep records of their sales for 20 years“ATF Guidebook: Importation & Verification of Firearms, Ammunition, and Implements of War.” Bureau of Alcohol, Tobacco, Firearms, and Explosives. and to run background checks before selling or transferring firearms. Individuals who are not “engaged in the business” of selling, importing, or manufacturing firearms are not required by federal law to conduct background checks on people to whom they sell firearms.“Background Checks Reduce Crime and Save Lives.” Everytown for Gun Safety. January 2015. Seventeen states currently go beyond federal law and require background checks on handgun sales by these unlicensed people as well.

National Instant Criminal Background Check System (NICS): A set of databases operated by the FBI that FFLs use to determine whether a person is eligible to purchase a firearm.“National Instant Criminal Background Check System.” Federal Bureau of Investigation. Before completing a sale, the FFL calls the FBI or a designated agency for their state, who runs a background check on the prospective buyer to determine whether he or she is prohibited from possessing firearms. These checks typically takes 90 seconds or less.

Firearms Tracing: When a gun is recovered at a crime scene, law enforcement agencies can send the model and serial number to the ATF National Tracing Center, which will attempt to trace the gun back to its manufacturer and from there to the firearms dealer who first sold it, who should have retained a record including details on the original purchaser.National Tracing Center.” Bureau of Alcohol, Tobacco, Firearms, and Explosives.; “Background Checks for All Gun Sales Will save Lives and Help Police Catch Criminals.” Mayors Against Illegal Guns.

Time to Crime: The amount of time between the first legal purchase of a firearm and its recovery by law enforcement in a crime. Guns recovered within three years of their original purchase have a “short timeto-crime” and are more likely to have been trafficked.“Federal Programs.” US Department of Justice Office of Juvenile Justic and Delinquency Prevention.

Microstamping: This technology engraves a code (for example the firearm’s serial number, make, and model) on the firing pin of a semi-automatic firearm. Every time the gun is fired, the firing pin stamps this alphanumeric code on the shell before it is ejected. A microstamped casing recovered at a crime
scene will allow law enforcement to identify the gun’s first purchaser and start the investigation process. California requires microstamping in all new models of semiautomatic handguns sold in the state.