(rev 5/2/03)


This page describes the most common types of firearms and the "actions" of those firearms.

Select to learn about assault rifles and Saturday night specials."


The term "action" refers to characteristics of the mechanism that actually fires the cartridges, commonly (though incorrectly) called bullets, or the one that controls the way the cartridges are loaded into the firing chamber and the empty cases are removed.  Some actions are peculiar to the type of firearm, like "single action" and "double action" in revolvers.  Others, that are used in multiple types include BOLT, PUMP, SEMIAUTOMATIC, LEVER, and AUTOMATIC.


One broad category of firearms is HANDGUNS, which are guns designed to be held in one hand, and includes pistols, semiautomatic handguns, machine pistols, revolvers and "derringers".

Another broad category of firearms is "long guns," sometimes called "shoulder guns," which includes rifles and shotguns.

Finally, there are firearms that are not normally held by a person and must be rested on the ground or mounted on something.  Examples of these are large machine guns and guns that are mounted on aircraft, tanks, foundations, etc.  An anti-aircraft gun is an example.  When such guns are of caliber greater than .50 caliber, they are typically called "cannons."


When most people say "pistol" all they mean is "handgun."  However, for some purposes--like the FBI Unform Crime Report system--the term is used to mean "semiautomatic handgun, which is often called an "automatic" even if it isn't really."  However, a "machine" pistol is a fully automatic handgun, like the "UZI" you see in movies.  The term may also be used to refer to anything--including a single-shot or breech (rear) loading handgun--other than a revolver, as the US Bureau of Alcohol, Tobacco and Firearms (BATF) defines the term via the Code of Federal Regulations.

Both automatic and semiautomatic handguns are loaded with cartridges by first loading a container called a magazine, or loosely called a "clip", then inserting the magazine into the grip (handle) of the gun.  Such magazines can be made to hold a gazillion cartridges, but the ones that come with the handguns have limits of anywhere from five to 19 cartridges.


A revolver could be a "long" gun in that rifles (types of long guns) have been built using a "cylinder" to hold the cartridges in the gun preparatory to them being fired.  However, the word "revolver" is generally used to refer to a handgun that uses a cylindrical magazine called the "cylinder."  It is this cylinder from which the gun gets its name.

The cylinder is at the rear end of the barrel, with part of the frame behind it.  The cylinder has several holes (typically six) through it, pointing the same direction as the barrel.  One of these holes is behind the barrel and, in effect, forms an extension of it.  When the gun is loaded, a cartridge is placed in one or more of the holes.

The cartridge in the hole behind the barrel is fired, then the cylinder is rotated (i.e., "revolved") so that the next cartridge is behind the barrel ready to be fired.  The cartridge is fired by a "hammer" behind the frame being released to move forward under spring pressure to hit the "firing pin" that, in turn, strikes the "primer" at the back end of the cartridge.  This primer "explodes" setting off the powder inside the cartridge.  The hammer is released as a result of the trigger (under the cylinder) being pulled.

With a "single action" revolver, the cylinder is moved into position to fire the next cartridge by the user pulling back ("cocking") the hammer.  With a "double action" revolver, the cylinder can also be moved into position by the first part of the trigger pull, which also cocks the hammer.  This makes a double action revolver faster shooting than a single action revolver, but also reduces accuracy because more force is necessary to pull the trigger.  So a person desiring to maximize accuracy can also pull the hammer back on a double action revolver before pulling the trigger.



A "derringer" is a type of handgun that is very small and short.  It has one barrel or often two "barrels" (actually "bores") together in one barrel structure that hinges down in front to enable the cartridge(s) to be loaded directly into the back end of the barrel.  Such guns have been built with several bores.  The design is named after the inventor or an early maker of such guns, although with a spelling error.


A rifle is a gun that is designed to be held in two hands and usually has a barrel over 18 inches long and a "stock" that rests up against the shooter's shoulder when the gun is fired.  This stock helps to steady the firearm so that it can be aimed more accurately than a handheld firearm.  The firearm name comes from the treatment called "rifling" on the inside of the barrel.  This is a set of grooves that spiral down the length of the barrel.  These grooves cause the projectile to spin along its flight from the gun to the target.  This spin causes the projectile to fly straighter.


A shotgun is a long gun that looks somewhat like a traditional rifle on the outside.  But a shotgun is usually used to shoot a packet of "shot," like little beads.  Because of what it shoots, the inside of a shotgun barrel is not usually "rifled."  If the gun is used only to shoot big chunks of lead, called "slugs," the barrel may be rifled.  Most shotguns, however, are designed primarily to shoot the "shot" and, if the gun is used to shoot slugs, the slugs themselves usually have the grooves to cause the slugs to spin as they come out of the barrel.



A semiautomatic firearm is one that shoots one cartridge each time the trigger is pulled, but uses energy from the firing of each cartridge to eject the empty case and insert the next cartridge into the firing chamber of the gun.


A machine gun is a fully automatic "rifled" gun.  A fully automatic gun is one that shoots cartridges--usually rapidly--as long as the trigger is held.  For handheld guns, the term "machine gun" is usually used for rifles only, although there are "machine pistols."  Some (usually larger caliber) machine guns are mounted on or in tanks, aircraft, etc.  Some used by the military are mounted on tripods for field use.  A machine gun rifle that shoots cartridges of calibers that are normally used in handguns is called a sub-machinegun.  The old Thompson sub-machinegun ("Tommy gun") seen in war and prohibition era gangster movies is the most common example of this.



Many rifles and a few shotguns use "bolt action" to insert a cartridge into the firing chamber of the gun and to remove the unfired cartridge or the empty case after the cartridge is fired.  The "bolt" is a nearly cylindrical rod that fits in the gun behind the firing chamber.  It has two tabs that stick out into channels in the gun frame, and these tabs turn into cuts off to the sides of the main channels to lock the bolt into position when the bolt is "closed" behind the cartridge in the firing chamber.

The bolt pushes the cartridge into the chamber, and is then turned to lock in place and make a totally enclosed firing chamber except for the bore of the barrel in front of the cartridge.  Turning the bolt back, then pulling the bolt to the rear, pulls out the cartridge or the empty case and ejects it. .  A handle that sticks out to the side of the bolt near the rear end is used to move the bolt in and out and to turn it into and out of the locked position.



Moderate numbers of both rifles and shotguns use "pump action" to enter and eject cartridges and cases into and out of the gun firing chamber.  The "pump" is under the barrel out in front of the trigger when a cartridge/case is not being moved.  There, it serves as a device to hold the gun and steady it the same as gun stocks on some guns.  To eject a case and load the next cartridge, the pump is pulled back as far as it will go toward the rear end of the gun, then pushed back out to the far position.



A lever action is mostly used on rifles, but a few shotguns have been made with lever action.  The lever is located under the trigger and a bit behind the trigger.  Part of the lever even functions as the trigger guard, the device that keeps things from bumping the trigger and accidentally firing the gun.  The lever hinges at a point forward of the trigger.  To eject a cartridge or empty case from the gun firing chamber, the rear (handle) end of the lever is pushed forward.  Bringing the lever back into the firing position loads a cartridge into the firing chamber, if the gun magazine was not empty, and cocks the hammer so that the gun is ready to fire again.  The lever action rifle was the first "repeating" rifle and appears in "western" movies about the cowboys, cavalry and indians.



An assault rifle is a rifle used by militaries.  It has a switch that permits it to fire like a semiautomatic rifle or as a fully automatic rifle.  Some also have a switch position that causes the gun to shoot a short burst of several shots each time the trigger is pulled.  Compare to what laws and gun control advocates call ASSAULT WEAPONS.