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Gun Vocabulary Words
ACP - Automatic Colt Pistol. Colt's proprietary designation for a type of rimless cartridge design for
reliable feeding from the magazine in a semi-automatic handgun. Example: .45 ACP
Action - The receiver of a gun containing the breech-locking and firing mechanism. The seriallynumbered, legal soul of a firearm. Major types are: Boxlock, Sidelock, Blitz, Falling Block and Bolt
Ambidextrous Safety - A safety catch that can be operated by either hand. Of benefit to left-handed
shooters and in the event of an injury to the right hand.
Automatic [Action] - A type of firearm which, utilizing some of the recoil or some of the
expanding-gas energy from the firing cartridge, cycles the action to eject the spent shell, to
chamber a fresh one from a magazine, to cock the mainspring and to fire again. Such a firearm
will fire continuously as long as the trigger is held back, until the magazine is empty. A machine
gun. A firearm thus activated, but which shoots only one bullet with each separate pull of the
trigger, while often erroneously referred to as "automatic" is more properly termed SemiAutomatic.
Automatic Safety - A safety catch on a break-open gun that resets to the "safe" position each
time the gun is opened, usually via a limb attached to the toplever spindle
Backstrap - Rear, metal, part of a handgun---which together with the frontstrap, provides a mounting
frame for the grips
Ballistics - The study of the action of propellant powders upon projectiles, their speeds, energies and
trajectories. Ballistics can be categorized into three phases: Interior (the projectile's behavior inside the
bore), Exterior (the projectile's behavior in flight), and Terminal (the projectile's behavior upon contact
with the target).
Barrel - An essential component of a firearm; a tube, sealed at one end (the breech) in which a
propellant is ignited, whose rapidly expanding gasses create powerful pressure to force a single or
multiple projectiles through its bore, out the open end (the muzzle) and down range towards a target.
Barrel Length - The length of a barrel as measured from the muzzle to the standing breech in a breakopen gun or to the bolt face in a closed bolt-action rifle, including the chamber. A revolver barrel
measurement, by convention, does not include the cylinder, only the barrel itself.
[In] Battery - A condition of a firearm where it is loaded, with the action closed, cocked and (with the
possible exception of the safety catch) ready to fire
Bayonet - A knife, optionally mountable to the muzzle-end of a rifle or musket to add the function of a
spear. For close-range combat and as a last resort when the ammunition is exhausted
Benchrest - (1) A stout table from which to fire a rifle, removing as much human error as possible in the
interest of testing rifles, loads and/or adjusting sights. (2) Both a type of rifle and the competition in
which it is used. A heavy, invariably single shot rifle, made for stationary target shooting. The rifle often
having a flat underside for unaided stability on the bench. An exercise for ultimate accuracy of rifle and
load with the variables of human marksmanship purged from the formula.
Bipod - A two-legged stand, usually hinged and attached to the forend of a rifle, for use as a rest in the
interest of increased stability in aiming
Black Powder- The first successful propellant harnessed for use in firearms. Composed, generally of 3
parts potassium nitrate, 2 parts powdered charcoal and 1 part sulphur. Black powder explodes--expending its energy in an instant of time, produces volumes of vision-impairing smoke, its residue
promotes rust in gun bores and it is unpredictably dangerous to handle. Black powder was replaced in
the marketplace by nitro-glycerin-based powders around the turn of the last century because they
burned more slowly (maintaining pressure on the projectile longer during its travel through the bore,
allowing higher velocities), did not blind shooters with the smoke, did not promote rust in bores and was
much safer to store and to handle. For these reasons, it is dangerous to shoot modern nitro powders in
vintage guns (such as those with barrels of damascus steel) originally designed and contoured for the
pressure curve of Black Powder
Blue - A chemical rust process that produces a very dark, almost black, blue finish to the steel parts of a
firearm which enhances the appearance and provides some protection from unwanted rust. Sometimes
it can have a slight brownish undertone. The percentage of blue finish remaining on a gun can be a
proxy for describing its condition
Bolt - A cylindrical shaft, controlled by an attached lever, which rotates a partial revolution engaging
locking lugs in complementary recesses, contains an internal spring-loaded firing pin, and becomes the
breech-block of a bolt-action firearm
Bolt Action - An action type, most frequently used on rifles, perfected by Peter Paul Mauser in 1898,
whereby a cylindrical shaft, controlled by an attached lever, manually feeds a cartridge into the
chamber, rotates a partial revolution engaging locking lugs in complementary recesses in the front
receiver ring, allows firing by the fall of an internal spring-loaded pin, opening, extraction, re-cocking
and ejection with the same lever in preparation for the next shot
Bolt Stop - A displaceable flange, usually towards the rear of a bolt action firearm which in normal
position, either detented or under spring tension, prevents the bolt from falling completely out the rear
when cycling the action. It is readily moved aside by the bolt stop release to allow removal of the bolt
for cleaning or disassembly
Bore Sight (v) - A process by which sights are adjusted to converge on the same line as the bore.
Accomplished by placing a rifle in a rest, sighting down the open bore on a prominent distant point at an
appropriate range, then aligning the sights to superimpose on the same point. Alternatively, may be
accomplished with a device known as a collimator. The process should conserve ammunition when
sighting-in a rifle by approaching proper sight adjustment before actually firing the rifle with live
ammunition
Butt - The end of a gun stock; the part that rests on the shoulder when the gun is mounted
Cal. or Calibre - System of measurement for the internal bore diameter of a rifled-barreled firearm (rifle
or pistol) based on the decimal part of an inch. For example, .25 calibre and .250 calibre both signify a
bore size of 1/4 inch. American calibre designations refer to the distance from land to land, not groove
to groove. Ammunition companies' marketing departments occasionally take liberties with exact
measurements. For example, a .270 Winchester bullet actually measures .277 inch in diameter
Cant (v) - To tilt a gun to one side or the other, complicating sighting considerably. Can cause material
loss of accuracy, particularly with a rifle at longer ranges. Some better long range target rifles are
equipped with Spirit Level sights to help the marksman control canting
Carbine - A general term referring to relatively short-barreled, quick-handling rifle, often intended for
use on horseback. In Winchester lever-action terminology, a carbine has a single barrel band. In
German, a Stutzen.
Cartridge - In its definition valid from circa 1870 to the present: a small usually cylindrical packet,
containing a detonating primer, a powder charge, a load---either a single projectile for a rifle or a
quantity of small pellets for a shotgun---and possibly some attendant wadding. The cartridge is placed
into the breech of a firearm, comprising all required consumables for the firing of the weapon
Chamber - An area at the breech end of a barrel, of about the diameter of the cartridge for which the
gun was intended, and into which the cartridge is inserted. The nominal length of a shotgun chamber
will accommodate the loaded cartridge for which it was intended and allow for its crimp to open fully
when the cartridge is fired. Although one can easily insert a longer-than-nominal-length loaded cartridge
in a shotgun chamber, it is not advisable to do so because when it is fired the crimp will open into the
forcing cone. Because of the taper of the forcing cone, the crimp will not be able to open fully and the
gun will develop far greater pressure than it was designed to handle.
Choke - A carefully measured constriction of the bore of a shotgun at the muzzle, designed to control
the spread of the shot as it leaves the barrel.
Choke tubes - Short, interchangeable cylinders, of subtly different internal tapers, that screw into a
threaded recess at the muzzle of a shotgun. By inserting different choke tubes, one can alter the shot
pattern thrown by the gun. Choke tubes should be tightened until snug. Guns fitted for choke tubes
should never be fired without tubes in place.
Clip - A simple, disposable narrow spring-lined channel-rail in which cartridges are supplied for military
weapons. The shooter positions the clip vertically above the firearm's magazine, then pressing down
with the thumb, slides the cartridges from the clip and down into the magazine. Also: Stripper Clip or
Charger (THIS IS DIFFERENT THEN A MAGAZINE THAT HOLDS BULLETS)
Cock (n) - A firearm's exposed hammer.
Cock (v) - To tension the mainspring of a gun in preparation for firing, such as by pulling back
the external hammer, pulling back the slide of a pistol, or opening and closing the barrel(s) of a
break-open gun.
Cocker/De-Cocker - A type of action on a break-open gun or rifle where, in place of a
traditional top tang safety, a somewhat more robust tab is fitted. Normally such a gun is carried
in the field loaded, but with the action not cocked---an exceedingly safe condition. Then, when
ready to fire, the shooter, instead of pushing a safety tab forward, pushes this larger tab forward,
cocking the mainspring, making the gun ready to fire. Then, if the shot is not taken, he may
simply slide this tab rearwards again, de-cocking the gun and returning it to the still-loaded, but
very safe position. Or, in German: Handspanner.
Cocking Indicators - Small devices attached to the internal hammers of a break-open gun and
visible from the exterior of the gun to show when each lock is cocked and when it has been fired.
These are usually in the form of protruding pins on a boxlock gun or in the form of engraved or
gold inlaid lines on the tumbler pins of a sidelock gun
Crosshairs - Basic form of telescopic sight reticle, having one fine vertical line and one fine horizontal line
with which to establish the point of aim.
Cylinder - That part of a modern revolver that holds cartridges in separate chambers radially around a
central hingepin. The cylinder revolves as the handgun is cocked, bringing each successive cartridge into
position, and locked into alignment with the barrel for firing.
DA or Double Action - An action type, typical on revolvers, where pulling the trigger through a long
stroke revolves the cylinder, cocks the hammer and fires the gun---and alternatively, where manually
cocking the hammer and then pulling the resulting single-stage trigger fires it also.
Deringer - A small, single-shot, percussion pistol designed and manufactured by Henry Deringer
of Philadelphia.
Derringer - Spelled with two rs, any very small easily concealed handgun.
Double Action - An action type, typical on handguns, where the hammer may be cocked
manually prior to each shot, OR, one may pull the trigger through a long throw which cocks the
hammer (and in the case of a revolver, advances the cylinder) and fires the revolver in one
complete motion
Dust Cover - A small hinged or sliding door covering the ejection port of a firearm to prevent
detritus from clogging the works.
Ejectors - Fittings inset into the breech end of a pair of barrels of a break-open gun that kick out
fired shells, while only raising unfired shells enough to be removed by hand. Recognizable at a
glance on the breech end of a double gun because the fitting is split in two---one ejector for each
barrel.
Elevation - Adjustment of the point of impact of a firearm in the vertical plane; the knob used on
an iron sight or telescopic sight to raise or lower the point of impact. Photo
Energy - Capability to perform work. As measured in foot-pounds, the amount of force it takes
to lift and object weighing one pound, one foot. To calculate the energy, in foot-pounds, of a
bullet in flight at any point on its trajectory:
W = Weight of the bullet in grains.
V = Velocity in feet per second
Erosion - Deterioration of the inner surface of a firearm's barrel due to the intense heat of a
cartridge's discharge. High-velocity rifles are particularly susceptible to this wear, especially near
the throat.
Extractors - A fitting inset into the breech end of a pair of barrels of a break-open gun. When
the gun is opened the extractor lifts the cartridges so they may be removed by hand.
Recognizable at a glance on the breech end of a double gun because the fitting is solid---one
extractor taking care of both barrels together.
Eye Dominance - Although we have two eyes for depth perception and for spare parts, there is a
natural tendency for one eye (the master eye) to take precedence over the other, regardless of the
relative visual acuity of each eye. It is a fortunate condition when the eye on the side of the
shoulder where one is comfortable mounting a gun is also the dominant eye.
To test for eye dominance, pick out a small object several feet away. With both eyes open,
center your right index finger vertically over the object. Close your right eye. If your finger
appears to jump to the right, you are right eye dominant. Then open your right eye and close your
left eye. If your finger remains in position in front of the object, you have confirmed your right
eye dominance. Alternatively, if in the above test, upon closing your right eye your finger
remains in position covering the object, you are left eye dominant. If you close your left eye
instead and your finger appears to jump to the left you have confirmed your left eye dominance.
Eye dominance problems can be treated with 1. A severely-cast, crossover stock to bring the
dominant eye in line with the gun's line of sight, 2. A patch over the dominant eye, or just a small
piece of frosty Scotch tape on shooting glasses intercepting the dominant eye's line of sight, 3.
Fully or partially closing the dominant eye, or 4. Learning to shoot from the dominant-eye
shoulder. While less convenient, methods that retain the use of both eyes better preserve the
ability to perceive depth in three-dimensional space---a great benefit in wingshooting.
Eye Relief - The distance that equates the exit pupil size of a rifle scope's ocular lens to the
entrance pupil of the user, in order to achieve the largest, unvignetted view. This distance must
be sufficient to ensure that the ocular rim of the scope does not lacerate the shooter's eyebrow
upon recoil. And, the scope should be positioned so that eye relief is suitable when the rifle is
comfortably mounted.
Feed Ramp - An inclined, polished area on a repeating firearm, just behind the chamber, that
helps guide a cartridge into the chamber when pushed forward by the closing bolt
FFL - Federal Firearms [Dealer's] License. Under federal law, to ship a firearm, a selling dealer
must have in his possession a copy of the receiving dealer's license
Firearm - A device which, on demand by activating some sort of switch like a trigger, ignites a
very-rapidly burning propellant or an explosive, expels a projectile such as a bullet, or projectiles
such as shot, from a tubular barrel (or barrels) with sufficient force as to cause acute bodily harm
to the target, animal, or person which it hits.
Flinch (v) - To jerk a firearm off target inadvertently at the instant of firing in timid anticipation
of recoil.
Fluid Steel barrels - Barrels made of homogeneous steel (not damascus steel) --- standard
practice for over a century
Fluted Barrel - A rifle or pistol barrel, into which longitudinal grooves have been milled. Fluted
barrels, while more expensive to make than round barrels, dissipate heat more rapidly and they
provide a better stiffness-to-weight ratio.
Follower - A smooth, sometimes contoured plate, within a magazine, at the top of a spring,
across which cartridges slide when being loaded into a chamber
Frontstrap - Front, metal, part of a handgun's grip---which together with the backstrap, provides
a mounting frame for the grip panels
Gauge - System of measurement for the internal bore diameter of a smooth-bore firearm based
on the diameter of each of that number of spherical lead balls whose total weight equals one
pound. The internal diameter of a 12 gauge shotgun barrel is therefore equal to the diameter of a
lead ball weighing 1/12 pound, which happens to be .729" (Or in British: Bore.) The Gauge/Bore
system is also used, by convention, to describe the internal barrel diameter of large-bore, 19th
century, English, single-shot and double-barrel rifles
Grain - A unit of weight widely used to express the weight of bullets and of powder charges.
Equal to 1/7000 pound.
Grip Safety - An interlock, often found on semi-automatic handguns, which helps prevent
accidental discharge while adding no perceptible inconvenience when firing the arm
intentionally. By the mere act of gripping the pistol in the hand, the shooter operates the grip
safety, releasing its lock on the firing mechanism
Grooves - The cut-away, concave portions of the rifling inside the barrel of a firearm
discharging a single projectile
Group - A set of holes in a target left by a succession of bullets fired from the same rifle or
handgun, using the same ammunition and sight setting. Fired (within the limits of one's
marksmanship ability) to determine the inherent accuracy of the rifle/ammunition combination--and to aid in the proper adjustment of the sights
Gun - (American) A firearm. (British) 1. A shotgun. 2. A person shooting a shotgun from a butt
at a formal driven shoot.
Half Cock - A middle position for an external hammer that effectively provides a safety
function. With a firearm with non-rebounding hammers, when on half-cock, the firing pin will
not rest on the firing-pin. And, whether rebounding or non-rebounding, an inadvertent pull of the
trigger should not release the hammer and fire the gun
Hammer - The part of a gun lock, which driven by a spring and released by a pull of the trigger,
falls and (usually via an intervening firing pin) strikes the detonating primer of the load and
discharges the gun. Hammers may be external or internal
Hammerless - A firearm with a coil-spring-actuated firing pin, or with its hammer enclosed
inside the action body; i.e.. no externally visible hammer
Handgun - A small, short-barreled firearm, possibly small enough to be concealed on the
person, and able to be held and discharged in one hand. The term includes antique dueling
pistols, modern single-shot, semi-automatic pistols and revolvers.
Handloading - The process of assembling cartridge case, bullet or shot, wads and primer to
produce a complete cartridge with the use of hand tools in the interest of loading for firearms for
which cartridges are not available, experimenting with loads to achieve better performance, or to
save money. Not to be attempted without knowledgeable instruction and careful study of the
process.
Hang Fire - A dangerous situation resulting occasionally from the use of outdated old
ammunition where the primer does not fire instantly upon being struck by the firing pin. The
cartridge may fire in a virtual instant or some seconds later. In the event that a cartridge fails to
fire immediately upon the pull of the trigger, always count out ten seconds before opening the
breech.
Heat Treating [Carbon Steel] - A process to achieve the desired balance between hardness and
resilience for the intended purpose of the metal. First, the steel is heated to above its austenitic
temperature (around 1800°F depending on the alloy; glowing orange, and no longer magnetic).
Then, is quenched in water or oil to cool it as rapidly as possible. Now, exceptionally hard and
too brittle for most applications, it is re-heated to a specific lower temperature than before and
quenched again, relieving the desired amount of its hardness.
Hollow-Point - A bullet type with a concavity at its tip, designed to promote expansion upon
hitting a solid target
Iron Sights - A set of two metallic protuberances fitted normally to the top of a firearm; one near
the muzzle and the other near the breech, which when adjusted and aligned properly with the
target, aid in the placing of the projectile in the desired location---as opposed to a telescopic
sight.
Keyhole - The tendency of a bullet to tip in flight and hit a target sideways, leaving a distinctly
oblong hole. This destabilization of the spinning bullet in flight is typically caused by a bullet
weight inappropriate for the rate of twist of the rifled barrel, an out-of-balance bullet or its
having nicked an impediment such as a blade of grass, in flight.
Magazine - A spring-operated reservoir for cartridges for a repeating firearm; often removable.
Magazine Follower - A plate, mounted to the top of a spring, inside a magazine, over which
cartridges may slide smoothly as they are guided into the chamber of a repeating firearm.
Mag. or Magnum - A marketing term for a cartridge of greater than normal power or velocity--and of the firearm designed to handle it safely.
Minute of Angle; MOA - A 1/60th part of a degree, the unit of measure used in adjusting rifle
sights. As it turns out conveniently, a minute of angle translates almost exactly to one inch at 100
yards (actually 1.047 inches), to two inches at 200 yards and three inches at 300 yards
Misfire - A dangerous situation resulting typically from the use of outdated old ammunition
where the primer does not fire upon being struck by the firing pin. The cartridge may fire in a
virtual instant or some seconds later---a hangfire. In the event that a cartridge fails to fire
immediately upon the pull of the trigger, always count out ten seconds before opening the breech
Muzzle - The end of a barrel, pointing towards the target, out of which the load is discharged.
Muzzle Brake - A fitting attached to the muzzle of a firearm, with a series of perforations
designed to deflect some of the forward-rushing gasses and pull the firearm forward off the
shoulder, reducing recoil. While muzzle brakes can be effective in reducing recoil, their resultant
blast is at least mildly offensive to anyone else standing nearby.
Muzzle Energy - The power of a projectile or a load of shot at the point that it exits the muzzle
of a firearm, normally expressed in foot-pounds.
Muzzle Velocity - The speed of a projectile or a load of shot at the point that it exits the muzzle
of a firearm, normally expressed feet per second.
NIB - New, unfired, in original box
NRA - National Rifle Association - Since 1871, promoter of firearms knowledge,
marksmanship and safety. Defender of our right to own and to use firearms. Everyone with an
interest in guns, and in freedom should be a member
Open Sight - A metallic attachment to a firearm, designed as an aid in aiming; an iron sight---as
opposed to an optical or telescopic sight
+P - A marketing term for a commercial (usually handgun) cartridge loaded a bit more
powerfully than its dimensionally-interchangeable, standard counterpart
Parkerizing - A chemical phosphate process developed during the second world war to provide
an economical, durable and non-reflective surface finish to military firearms
Patch - A small piece of cloth, wrapped around a ball when loading a muzzle-loading firearm, or
attached to a rod for cleaning the bore of a firearm after use.
Picatinny Rail - A metal bar, available in a variety of lengths, with a continuous row of Weaverlike scope mount base slots, which when attached to a firearm, allow convenient attachment of a
variety of sights, lights, slings, bipods and other accessories designed to fit this standard system
Pistol - A short-barreled firearm, often concealable, normally held and discharged in one hand.
In today's vernacular, especially a semi-automatic, repeating handgun---as opposed to a revolver.
But, the term can actually mean any one-hand-held firearm: matchlock, flintlock, percussion or
the latest technology from Heckler&Koch.
Pistol Grip - The generally-vertical part of the stock of a rifle or shotgun held by the triggerfinger hand---as opposed to a straight English grip---resembling the grip on a handgun.
Ported barrels - Barrels with a series of holes or slots drilled near the muzzle. When a ported
barrel is discharged, gasses moving violently down the barrel hit the forward edge of the holes
and pull the gun forward off the shoulder, reducing felt recoil. Porting holes, when cut along the
top of the barrel also work to depress the barrel under discharge, counteracting muzzle jump.
Ported barrels may provide some benefit to the shooter, but the sideways blast of gas is
somewhat obnoxious for others nearby.
Primer - A small capsule of soft metal containing a detonating compound, press-fitted into the
head of a cartridge. When the primer is struck by the firing pin, the small charge explodes,
touching off the main powder charge inside the cartridge, launching the bullet or shot charge
QD - Quick-detachable, as in scope mounts or sling swivels.
Rail Mount - A telescopic sight with an integral rail on the underside. The rail provides rigidity
to the scope and it provides a convenient point of attachment for a typically European quickdetachable mounting system. Longitudinal positioning is more flexible because the rail is less
obstructed by objective or ocular bells and windage/elevation turrets.
Receiver - The frame or action body of a firearm. The housing that contains the mechanism that
fires the gun. The serially-numbered part which legally constitutes the firearm. Photo
Recoil - The tendency of a firearm when fired to move backwards, and a little upwards as a
reaction to the force of the projectile moving down the barrel. As Newton says, to every action
there is always an equal and opposite reaction. The mass of the firearm provides some inertia to
counteract the momentum of recoil. What remains is absorbed by at the shoulder or the hand.
The heavier the gun, the less the recoil. The more powerful the cartridge, the more the recoil.
Recoil Pad - A soft appendage, usually of some kind of rubber, often fitted to the butt end of a
shoulder-mounted firearm to reduce the sensation of recoil. A recoil pad has the additional
benefit of being less vulnerable to damage than a checkered wood butt or a brittle horn or plastic
buttplate
Reticle - A matrix of dots, posts or lines, visible inside a rifle's telescopic sight, normally
adjustable via exterior knobs for windage and elevation. After careful adjustment at a known
range, the shooter aims the rifle by superimposing this matrix onto the target. With good
estimation or range, cooperation from the wind, a clear eye and a steady hand, he may have a
reasonable expectation of hitting his target. Also, less correctly: Reticule. Or, in British:
Graticule.
Revolver - A firearm (normally a handgun) with a multiple-chambered cylinder which rotates
incrementally to bring each successive loaded chamber into battery. .
Rifle - A shoulder-mounted firearm, having a series of spiral grooves (rifling) cut inside the
barrel that impart a rapid spin to the single projectile, gyroscopically stabilizing it in flight for
greatly improved accuracy over that of a smoothbore gun.
Rifling - Spiral grooves cut into the inside of a barrel that impart a rapid spin to the single
projectile, gyroscopically stabilizing it in flight for greatly improved accuracy over that of a
smoothbore gun.
Rim - A flange at the base of a cartridge case that provides purchase for the firearm's extractor to
grasp and remove or eject the spent case.
Rimfire firearms cartridges have their priming compound spun by centrifugal force into the
crevice of the hollow rim on sophisticated equipment in factories. Rimfire cartridges, such as the
.22 Long Rifle, cannot be reloaded with consumer equipment, at home. Rimfire cartridges are
detonated when the firing pin hits the edge of the base of the cartridge and pinches the priming
compound between the folds of the rim.
Safety - A device, incorporated into the design of most firearms actions that, when engaged,
should prevent the discharge of the firearm. Some safeties are more positive than others. A safety
device is not a perfect substitute for the general principles of responsible gun handling. Never
point a gun in a direction you do not intend to shoot.
Select Fire - A firearm with a switch allowing a choice of either semi-automatic operation or
fully-automatic [machinegun] operation. The State of Connecticut tried to write a law prohibiting
machineguns, but they thought they were being sophisticated by using the term Select Fire
instead of the more plebeian Machinegun. Consequently, firearms that operate in fully automatic
mode only, are not prohibited in Connecticut.
Semi-Automatic [Action] - A type of firearm which, utilizing some of the recoil or some of the
expanding-gas energy from the firing cartridge, cycles the action to eject the spent shell, to
chamber a fresh one from a magazine and to cock the mainspring, placing the gun in position for
another shot with nothing more needing to be done than to provide another pull on the trigger.
Autoloader. Often erroneously referred to as automatic---but automatic actually refers to a
machine gun. The Colt Model 1911 pistol and the Browning Auto-5 are semi-automatic designs.
Shotgun - A shoulder-mounted firearm with one or two (or very occasionally more) smoothbore
barrels through which is fired a charge of a small handful of tiny pellets, usually at flying birds
or other moving targets.
Sight Radius - The distance between the front and rear sights. As a longer lever provides greater
mechanical advantage, the greater the distance between the two sights, the more inherently
accurate they will be.
Single Action - An action type, typical on handguns, where the hammer must be cocked
manually prior to each shot (if it be a revolver) or prior to the first shot with an already loaded
chamber and de-cocked hammer (if it be a semi-automatic).
Snap Caps - Dummy cartridges with spring-loaded "primers" used to test the mechanical
functioning of a firearm, particularly the trigger pulls, hammer-fall and ejector-timing of a breakopen gun. It is not advisable to dry-fire a break-open gun on an empty chamber. Hardened steel
parts can shatter without the soft brass primer to act as a shock absorber. Snap caps cushion the
blow of the hammer and firing-pin when the use of a live cartridge would be impractical
Squib Load - An underpowered powder charge, usually caused by a fault in cartridge loading,
often insufficient to expel a projectile from the muzzle of a firearm, If such a blockage is not
noticed and cleared, the bullet from the next attempted shot could be blocked, causing the barrel
at least to bulge, and very possibly to burst.
Stripper Clip - An expendable retainer for a small quantity of cartridges suitable for filling the
magazine of a repeating firearm
Takedown - A firearm that can be separated into (at least) two subassemblies in order to make a
shorter package than when put together---without tools. There is no specific requirement
regarding how this disassembly must be accomplished; the mechanical design is up to the
creativity of the maker. This arrangement allows for more convenient transportation of a firearm,
but with rifles, where the action normally separates from the barrel, usually at a small sacrifice in
accuracy.
Telescopic Sight - An optical sight, offering some magnification, often variable, with some kind
of adjustable aiming grid inside (a reticle), which when mounted on a firearm, usually a rifle,
makes sighting easier
Trajectory - The arc described by a projectile (or a load of shot) after it exits the muzzle of a
firearm. Falling objects accelerate downwards at a rate of 32 feet per second, per second. The
faster a projectile travels, the greater the distance it can cover in a given time before dropping too
far. Hence, the higher the velocity of a bullet, the flatter the trajectory it will achieve.
Trigger - The small lever on a cartridge firearm, which one pulls to cause the spring-loaded
firing pin to impact the primer, causing the gun to discharge. Normally, the trigger simply
connects to the sear. Pulling the trigger moves the sear out of its notch, releasing the springloaded hammer to strike the firing pin which in turn strikes the primer; or the coilspring-loaded
firing pin directly. Other, often-Germanic systems have their own miniature lockwork which,
when cocked, allows an exceedingly light trigger pull to discharge the firearm---a setting that
would be perilous to carry in the field.
Triggerguard - A bow-shaped flange, normally made of steel, but sometimes of horn or other
material, designed to cover the trigger well enough to reduce the possibility of accidental
discharge, while not being so obtrusive as to prevent the firing of a quick shot.
Twist - The length, within a rifled barrel, required to accomplish one full rotation. 1:12 Twist,
means a bullet passing down the bore would complete one revolution in twelve inches. Different
weights of bullet require appropriate rates of twist.
Windage - Adjusting the point of impact of a firearm in the horizontal plane; the knob used on
an iron sight or telescopic sight to move the point of impact in traverse, right or left, to
compensate for the effects of wind
Zero (v) - To adjust the sights of a firearm so that, with competent marksmanship, the projectile
should hit the desired target
Source: http://www.hallowellco.com/abbrevia.htm