Letter M

The Definition of Machine Gun

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Machine Gun

A fully automatic firearm that rapidly fires multiple rifle-caliber shots with a single pull of the trigger.

19 Other Firearms Definitions You Need To Know

Bolt Face

The forward end of the bolt which supports the base of the cartridge and contains the firing pin.


The point of a projectile.


Also known as a Case. The envelope (container) of a cartridge. For rifles and handguns it is usually of brass or other metal; for shotguns it is usually of paper or plastic with a metal head and is more often called a "shell."


Abbreviation for Double Triggers


A firearm is said to be on safe when its safety is engaged and off safe when it is ready to fire.

Match Grade

A higher quality item used to increase accuracy, generally used for competition in a match. Match grade ammo and barrels are the most common improvements made to a firearm to improve accuracy for competition.


Abbreviation for Concealed Firearms License.


The tunnel down the barrel of a firearm through which the projectiles travel.

  • A smooth-bore firearm is one that does not have rifling on the barrel's internal surface.
  • A big-bore firearm is one that fires a large caliber.
  • A small-bore firearm is one that fires a small caliber.


The diameter of the bore of a firearm measured as a fraction of an inch. Although such a measurement may be frequently stated in millimeters. It is correctly expressed as ".40 caliber" (note the decimal point) or as "10 millimeter" (without "caliber" or the leading decimal point). Caliber numbers when used to identify the size of the bullet a gun will file are usually followed by words or letters to create the complete name of the cartridge. These letters often represent a brand name or an abbreviation for the name of the company that first introduced the round.

Gas Check

A metal cup placed on the end of a lead bullet to protect the lead against the hot gases of the burning powder charge. Used in some types of firearms ammunition when non-jacketed bullets are used in high pressure cartridges, to prevent the buildup of lead in the barrel and aid in accuracy.


Violent Crime Control and Law Enforcement Act of 1994. It is an act of Congress dealing with crime and law enforcement that became law in 1994. Of the sections of the bill, it included the Federal Assault Weapons Ban.

Iron Sights

The mechanical sighting system which usually comes with the firearm made of metal with no optics.


Two shots fired very quickly with the use of the sights.

Overbore Ammunition

Small caliber bullets being used in large cases. E.g. .22 bullet in a .45 acp case.

Sporting Firearm

Any gun that can be used in a sport.

Smokeless Powder

The propellant powder used in modern ammunition. It is not an explosive, but rather a flammable solid that burns extremely rapidly releasing a large volume of gas. Commonly called "gunpowder" and usually made from nitrocellulose, or nitrocellulose and nitroglycerin. It is classified as a "Flammable Solid" by the Department of Transportation.

Rear Sight

The rear sight is placed at the end of the barrel nearest the shooter. It may be in the shape of a square notch, a U, a V, a ring, or simply two dots designed to be visually placed on either side of the front sight while shooting.


Slang word for short barreled revolver.


A heat-treating process that incorporates carbon into the surface molecular structure of the steel, providing a hard-wearing surface without making the entire receiver brittle. The parts to be casehardened are packed in a crucible with carbon-rich media such as bone meal and charcoal, heated to bright orange, about 1800F, then quenched in bubbling oil. Also called Carbonizing.