Accuracy

The measure of precision in consistently obtaining a desired result. In shooting, the measure of a bullet’s or gun’s ability to place all shots close to the same point.

Action

The mechanism of a firearm by which it is loaded, locked, fired and unloaded.

Adjustable Objective

In scopes, the front objective turns to focus the image. Most AO scopes also have yardage ticks to rangefind while focusing.

Air Resistance

The slowing effect of air on a projectile in flight.

Annealing  

In handloading, the controlled heating of brass after work-hardening to prevent it from becoming too brittle. Only the neck should be annealed, and great care should be taken not to overheat and thus soften the head and rear portion of the case. See Work-harden.

Antimony

A metallic element that increases the hardness of lead when combined as an alloy.

Anvil

In the priming system, a fixed metallic point against which the priming mixture is crushed and thereby detonated by the action of the firing pin. Boxer anvils are part of the primer; Berdan anvils are part of the cartridge case.

Ball

Early term for "bullet" due to the shape of the earliest projectiles being round lead balls. Still used in military nomenclature, usually to describe a full-metal jacketed bullet.

Ball Powder

Trademarked name for a double-base smokeless propellant powder developed by Olin, Inc. Both spherical or flattened spherical shapes are made.

Ballistic Coefficient (BC)   

Ratio of the sectional density of a bullet to its coefficient of form. Represents the projectile's ability to overcome the resistance of the air in flight. A bullet with a numerically high BC will meet less air resistance that a bullet with a low BC.

Ballistics

The science of projectiles in motion. Divided into interior ballistics— covering the time between the start of primer ignition and the bullet's exit from the barrel; exterior ballistics—the bullet's movement from barrel exit to target impact; and terminal ballistics —the bullet's behavior from the moment it enters its target until it stops moving.

Barrel-cylinder Gap

The clearance between barrel and cylinder in a revolver. In the U.S., the industry specification is 0.001" to .012". Revolvers with gaps larger that .012" can suffer a bullet lodged in the bore due to excessive gas loss through the over-spec gap.

Battery Cup

Type of primer in which anvil and primer cup are supported in an outside cup. Shotshell primers are of this type.

Bearing Surface   

The portion of a bullet's surface that actually touches the bore in moving through the barrel.

Bedding     

Manner in which the barrel and action of a rifle is fitted to the stock.

Bell

To expand the mouth of a case slightly in order to seat a bullet more easily. Also called flare.

Belted Case

Case head type with a raised band or belt at the base ahead of extractor groove. A variant of the rimless case. The belt acts to control headspace of the cartridge. See rim and rimless.

Bench Rest

A solid table or bench used for supporting a gun when testing for accuracy. Bench Rest target shooting has become an important shooting sport where the smallest group wins.

Berdan   

A centerfire priming system characterized by an anvil mounted in the case's primer pocket with one to three small, off-axis flash holes. Berdan primers have no anvil as the anvil is integral with the case. Poorly suited to reloading. Common in Europe, especially in military ammunition. Named for the inventor, Col. Hiram Berdan, an American.

Black Powder

The oldest ballistic propellant for muzzle loaders and early cartridge arms composed of a mechanical mixture of potassium nitrate (saltpeter), charcoal and sulfur.

Boat Tail

Name given to a bullet type with a tapered base due reduce aerodynamic drag.

Body (of a case) 

The section of a bottleneck cartridge case between the head and the shoulder that contains the powder.

Bolt

The locking and cartridge-supporting mechanism of a firearm that operates in line with the axis of the bore. It contains the firing pin, firing pin spring, extractor(s) and sometimes the ejector.

Bolt Thrust

The force on the face of the bolt or breech of a firearm caused by the pressure of burning powder gases. Bolt thrust acts on an axis parallel to the bore.

Bore

The inside of the barrel of a gun of any kind and, in rifled arms, the diameter of the barrel before the rifling is cut.

Bore Sight

To approximately align the sights of the firearm with a target by sighting through the bore.

Boxer

The standard American centerfire priming system, named after the inventor of this type of primer, Col. Edward Boxer of the British Army. Characterized by a large, on-axis flash hole in the case and the anvil mounted in the primer cup. See Primer.

Brass

An alloy of copper and zinc of which cartridge cases are usually made. This term is often applied to empty cartridge cases. Typical cartridge brass has a copper/zinc ratio of 70/30.

Brisance   

The characteristic in an explosive of brusqueness or shattering power. The more brisant an explosive, the more rapidly it detonates and the greater its relative power. In small arms, brisance is usually applied to priming compounds.

Bullet

The missile only. Becomes a projectile when in flight. Not to be applied to the term cartridge. See also ball.

Bullet Path

The track followed by a bullet in flight. It is described by the location of the projectile above (+) or below (–) the line-of sight at a given range.

Bullet Pull

The amount of force needed to extract a bullet from a loaded cartridge. Used by ammunition manufacturers to measure uniformity of crimp.

Bullet Puller

A tool for extracting bullets from loaded cartridges. The inertial and collet types are most common.

Burning Rate

A relative term used to rank the rapidity with which a given powder releases energy during burning in comparison with other powders.

Caliber    

A term that derives from Latin qua libra, meaning "what pound," first applied to the weight of a bullet and then to the diameter. Caliber now refers to the diameter of either a projectile or the bore of a gun. It is the approximate bore or groove diameter expressed (in English) in hundredths of an inch. A bullet that is 0.451" in diameter is 45 caliber. To write ".30 caliber" is technically incorrect. According to the strict definition, such a bullet would only be 0.003" in diameter! Frequently compounded with other descriptive words or numbers to create a cartridge name, e.g., 308 Winchester or 30-40 Krag. Also used in artillery as a measure of length equal to the diameter (or caliber) of a specified gun, as, a "fifty-four caliber" 5-inch naval rifle has a barrel that is 5x54", or 270 inches long. A "6 caliber" bullet ogive has a radius equal to 6 bullet diameters.

Canister Powder  

A propellant powder intended for retail sale to hobby handloaders. As these hobbyists do not have access to pressure testing equipment and rely instead on published load data, every effort is made to insure that lot-to-lot variation over time is minimized. "Non-canister" propellants are sold in bulk to ammo manufacturers who have pressure testing equipment.

Cannelure

Circumferential groove(s) around a bullet or cartridge case. Used for identification, to hold lubricant, or for securing the bullet in the case..

Cap  See primer.

Cartridge  

A complete unit of assembled ammunition: case, propellant powder, primer, and bullet. Commonly applied only to rifle and pistol ammunition, but technically correct for shotshells also.

Case

The paper, metal, or plastic container that holds all the other components of a cartridge. Sometimes called hull or shell.

Case Forming

To alter or modify one cartridge case to another of different shape and or caliber. Also see wildcat.

Case Hardening 

A heat treating process which increases the surface hardness of iron alloys. Often produces distinctive colors, such as seen on the frames of Colt Single Action revolvers.

Case Trimming    

Shortening an overly long case by removing metal at the case mouth.

Cast Bullet

Bullets for rifles or pistols cast from molten lead or lead alloy in a mould. See mould blocks

Center Fire (CF)

Refers to metallic cartridge case having a centrally located primer in the base. Also called centerfire. Most center fire cartridges are reloadable.

Chamber

That part of the barrel at the breech end, formed to accept and support the cartridge. In a revolver, chambers are located in the cylinder.

Chamber Cast

A casting, usually of sulfur or low melting-point metal, poured in the chamber to more easily measure chamber shape or condition.

Chamfer

To bevel or ream a taper on the inside of a case mouth to facilitate bullet seating.

Charge    

The amount of propellant powder measured into the case in loading. Also refers to amount of shot measured into shotshell.

Choke

A constriction at the muzzle of a shotgun barrel designed to control the spread, or dispersion, of the shot charge.

Chronograph

A mechanical or electronic device used to measure the velocity of a projectile.

Collimator   

In shooting, an optical device used to roughly align the sights with the bore of a rifle or handgun. Essentially, a collimator allows bore sighting without having to see through the barrel.

Combustion

Burning; in firearms, the chemical process which unites oxygen and other substances in gun powder to produce heat and gas. Also called deflagration.

Compensator

A device fitted to the muzzle of a firearm to reduce recoil or muzzle rotation. Usually applied to such devices when fitted to a handgun. See muzzle brake.

Components

The individual parts that go into the making of a cartridge.

Compressed Charge

A charge of powder which is compressed by the bullet during seating in the case.

Copper Crusher     

Small, solid copper cylinder used in a pressure gun to measure chamber pressure. See pressure gun.

Cordite 

Trade name for a long, tubular-grained, double-base powder used mainly in Great Britain, and one of the earliest smokeless propellants. The granules are often as long as the powder space.

Core

The interior part of a jacketed bullet; usually a lead alloy in sporting ammunition.

Corrosion

The eating away of the bore because of rusting or the chemical action of salts deposited in the bore by corrosive primers or powders. Cartridge cases can also be corroded by salts or acids.

Corrosive Primer

A primer whose burnt residue is hygroscopic (attracts moisture) and forms chemicals that can cause corrosion. These chemicals will rapidly rust a bore unless removed with a water-based solvent. All component primers in the U.S. have been non-corrosive for decades.

Crimp

The bending inward of the mouth of the case in order to grip the bullet, or to close the mouth of a shotshell case. Two types are used. A roll crimp is the bending or rolling the mouth of the case into the crimp groove or cannelure of the bullet. In a taper crimp, the mouth of the case is pressed into the bullet body without bending the case mouth.

Crimped Primer   

A forcing inward of the brass around the top of the primer pocket to prevent set-back of primers. This is usually found on military cartridges intended for use in fully automatic weapons. Unless the crimp is removed after depriming—either by swaging or reaming—repriming of the case is very difficult.

Cupro-Nickel

A copper-nickel alloy once used extensively for bullet jackets. It was largely replaced by gilding metal because of barrel fouling problems.

Deburr

To remove burrs or roughness sometimes left on case mouth edge by trimming operation. See chamfer.

Decap or Deprime

To remove or eject a primer from its primer pocket. Usually done by the decapping pin in the sizing or expanding operation.

Deterrent Coating

A chemical coating applied to the surface of powder granules to control the burning characteristics of the base powder. Aptly described as a "temporary fire-proofing" of a powder kernel.

Die

In handloading, a tool to form or reform cases or bullets by cold-working, or to seat bullets.

Double-base Powder

Nitrocellulose (smokeless) propellant that uses nitroglycerine as the plastisizer.

Drag

see air resistance

Dram Equivalent

In shotshells, a term used to indicate that a charge of smokeless powder produces the same velocity as a given number of drams of black powder. Thus, a 3 dram equivalent load has a charge of smokeless powder that gives the same velocity as a similar load charged with 3 drams of black powder. One dram equals 27.3 grains.

Drift

In exterior ballistics, the deviation of a projectile from the line of departure due to its rotation or spin. Also commonly but incorrectly applied to the effects of wind. See wind deflection.

Drop

The distance a projectile falls due to gravity, measured or calculated from the line of departure as it travels downrange. Must be corrected for difference between line of sight and line of departure. Drop is normally reported assuming a horizontal barrel.

Duplex Load

A dangerous condition that uses two different powders in loading the same cartridge. There is little or no advantage to duplex loading in small arms and results are unpredictably dangerous.

Elevation

The vertical adjustment of a sight to bring the point of aim into coincide with the desired point of impact.

Energy

The amount of work capable of being done by a projectile at a given range, expressed in foot-pounds in the English system. Found by multiplying the square of the velocity in feet/sec by the weight of the bullet in grains and dividing by 450,400.

Engraving

The marks made on the bullet by the rifling.

Erosion

The wearing away of the bore of a firearm due to friction from the projectile, the action of hot powder gases, or the abrasive effects of partially burned powder grains.

Expander Ball or Button

The round steel part of a die that expands the sized neck of a cartridge case to the diameter needed to hold the new bullet firmly.

Expansion Ratio     

Ratio of interior case volume to bore volume.

Extruded Primer

A primer that, on firing, has the metal of the primer cup forced back into the firing pin hole in the face of the bolt. Also known as cratering. Usually a gun problem, not a pressure sign.

Extruded Tubular Powder

Another term for cylindrical powder. Formed by forcing damp propellant mix through a die during manufacture and cutting to desired lengths. Usually has one or more longitudinal holes through the grains.

Extrusion 

A shaping process that forces a solid mass through a hole of smaller diameter to produce a wire; used in the manufacture of bullet cores.

Fireform

Using the pressure of normal firing to shape a cartridge case to fit a given chamber.

Firing Pin 

That part of a gun's mechanism that strikes the primer to start ignition.

Flake Powder

A smokeless powder characterized by thin, disc-shaped granules.

Flash Hole 

The hole leading from the primer pocket into the body of the cartridge case. Also called the vent.

FMJ

Full metal jacket. See metal case.

Foot-pound

A unit of kinetic energy in the English system defined as the effort required to raise one pound to a height of one foot against the force of gravity.

Forcing Cone

The slope of the forward end of the chamber of a rifle or shotgun which decreases the chamber diameter to bore diameter. In a revolver, the bevel in the rear of the barrel just ahead of the cylinder.

Form Factor

A multiplier which relates the shape of a bullet to the shape of the standard or reference projectile used to determine the ballistic coefficient.

FPS

Feet per second, a measure of velocity in the English system. Also feet/sec, ft/sec, or fs.

Freebore 

The distance, if any, which a bullet travels upon firing before it contacts the origin of the rifling.

Frontal Ignition  

Experimental type of cartridge ignition system where primer flash is directed to the forward part of the powder charge through a metal tube.

Galling

Friction between a case and sizing die producing roughness on the case and case metal deposited on the die surface.

Gas

In handloading, the vapor produced by burning powder. This heavy gas is capable of expanding rapidly, creating sufficient pressure to propel the bullet at high speed.

Gas Check

A copper or brass cup used to prevent hot, high-pressure powder gases from deforming the base of lead bullets.

Gas Ram

Similar to a spring gun in function, without the mainspring. A gas ram is a gas strut placed in the compression chamber of the rifle. Behind the piston is compressed air. When the airgun is cocked, the air is further compressed. When the airgun is fired the air expands and pushes the piston forward, compressing the air in front of the piston and thus fires the pellet.

Gauge

A term used to identify most shotgun bores, with the exception of the .410 shotgun. It relates to the number of bore diameter lead balls weighing one pound. Note: The .410 shotgun is a caliber. The .410 refers to the diameter of the barrel.

Gilding Metal

A copper-zinc alloy used for bullet jackets. Defined as 95 parts copper to 5 parts zinc. Commercial bronze (90 copper, 10 zinc) is also used for jackets.

Grain

In English weight measure, 7000 grains equal one pound; 437.5 grains equal one ounce. Incorrectly used in referring to a granule, or kernel, of powder. Thus "35 grains of powder" always refers to 35 of the weight-unit grains, never to 35 individual granules of powder.

Grand Slam

An honorary award to a hunter who has collected the four varieties of North American wild sheep. Also the trademark of the premium hunting bullet made by Speer.

Granulation

Refers to powder grain size and type. Can apply to either black or smokeless powder.

Grease Groove

Lubricating groove. On a lead bullet, a circumferential groove used to hold lubricant.

Grooves

Spiral cuts or impressions in the bore of a firearm that cause a bullet to spin as it moves through the barrel. See rifling.

Group

The pattern made at the target by a number of bullets fired with one aiming point and usually one sight setting. Usually measured from center to center of the holes farthest from each other.

Gun Powder

Propellant explosive used in small arms. Can be either smokeless or black powder.

Gun Show

A gun show is a temporary market for guns and ammunition, usually held at a meeting hall or fairground.

Half-jacket   

A short bullet jacket, or a bullet swaged with a short jacket, which leaves some lead in contact with the bore. A three-quarter jacket is similar but longer, so the bearing surface of the bullet is covered by the jacket material.

Handloading

The practice of loading or reloading small arms ammunition by hand-powered equipment and methods.

Hangfire  

Slang term for a delayed firing, which is any detectable delay in the ignition of a cartridge after pulling the trigger. Can be a chemical delay caused by the cartridge or a mechanical delay caused by a defect in the firearm. Chemical delays are recognized as being less that 0.3 second. The use of modern lead styphnate priming has virtually eliminated the chemical delay. Chemical delays were more common with the now-obsolete potassium chlorate priming compounds.

Headspace  

The distance from that surface of the barrel or chamber that prevents the cartridge from moving further forward into the chamber, to the face of the breech with the action fully closed and locked. This is the most important dimension governing the safety of the shooter.

Heel

The edge of the bullet base.

Holdover 

The vertical distance a shooter must aim above a target to obtain a hit at ranges greater than the gun's "zero." See zero.

Hollow Point (HP) 

Bullet design feature; an axial hole in the tip of a bullet to speed the release of energy into a target and reduce the chance of over-penetration.

Hot-Cor 

The trademark for Speer's exclusive process of manufacturing flat-base rifle bullets. A molten core is poured into a clinically clean jacket and then the bullet is immediately swaged to shape, with a resulting tight bond between core and jacket.

Hydrostatic Shock

A pressure wave created by a bullet passing through animal tissue, which is high in water content.

Ignition    

The initiation of burning, either of a priming compound or a propellant.

IHMSA

International Handgun Metallic Silhouette Association.

Improved

Term used to indicate a standard cartridge case which has been altered by fireforming to reduce body taper and/or increase shoulder angle. Improved cases have greater powder capacity than the corresponding standard case.

IMR

Abbreviation for "Improved Military Rifle," a trademark of DuPont (now IMR Powder Company) to its line of single-base rifle powders.

Ingalls' Tables      

Ballistic tables computed by Col. James M. Ingalls and first published in 1918. The most widely used ballistic tables in the U.S. prior to the development of computers.

IPSC

International Practical Shooting Confederation.

Jacket

The cover or "skin" of a bullet. Usually made of gilding metal in the U.S., but copper-clad mild steel is also used in other countries. See cupro-nickel and half-jacket.

K (used as a prefix) 

Applied to cartridge case improvements developed by experimenter Lysle Kilbourn. Example: the 22 K-Hornet.

Keyhole 

The elongated imprint of a bullet on a target that shows that the bullet was not traveling point-on at the time of impact.

Lands

The spiraling raised portion of a rifle barrels interior remaining after the grooves have been cut or formed.

Lead Crusher

A pure lead cylinder used in a pressure gun for obtaining lead units of pressure (L.U.P. or lup). Formerly used to test low-pressure cartridges such as shotshells, this system is now obsolete in the U.S.

Leade

See throat or freebore.

Leading  

Lead deposited in the bore from the friction of lead bullets rubbing against the bore, or from gas-cutting of lead bullets. A form of metal fouling, some leading is normal; however, excessive leading can destroy accuracy and raise pressures.

Line of Departure

The straight line at which a bullet leaves the muzzle of a firearm, equivalent to the axis of the bore extended into space. The bullet immediately falls away from this imaginary line due to gravity.

Line of Sight (LOS)

The straight line through the sights of a gun to the point of aim.

Loading Block

A block of material, usually wood or plastic, with rows of holes to conveniently hold a number of cartridge cases during the loading operation. Especially useful when charging cases with a powder measure.

Loading Density

Ratio of the volume of powder charge to the volume of the case.

Lock Time  

The period of time between the release of the sear by trigger movement and the instant the priming mixture detonates after being hit by the firing pin.

Locking Lugs

Protrusions on the bolt which engage a mating recess inside the receiver ring when the bolt is closed. This feature prevents the bolt from moving rearward when the rifle is fired. Usually used in reference to rotary bolt-action firearms.

Lubricant     

Case sizing lubricant is used to reduce friction when sizing cartridge cases. Bullet lubricant is used to help minimize leading when firing lead alloy bullets.

Lubricator-Sizer      

A tool used to simultaneously size and lubricate cast lead bullets.

Magnum

A cartridge of exceptional size or power.

Mean Radius (MR)

The average radius of a group of shots from the center of the group. Another method of recording accuracy, MR is commonly seen in military contract specifications for accuracy. Extreme spread is more commonly used to measure accuracy in commercial ammo manufacturing and hobby shooting.

Meplat

The flat or blunt end of the nose of a bullet.

Mercuric Primer

A primer in which the primary initiator is mercury fulminate. These primers have been obsolete since the advent of metallic cartridge reloading over a century ago. On firing, the compounds release minute amounts of metallic mercury. Mercury attacks the cartridge case making it brittle and thus unsuitable for further loading.

Metal Case (MC)

Also Full Patched (FP) or Full Metal Jacketed (FMJ). A type of bullet in which the core is completely encased in jacket material, except for an opening on the base. Standard military bullet type.

Metal Fouling

Bullet jacket material deposited in bore due to friction. More common in very high-velocity rifle cartridge, metal fouling must be removed to prevent corrosion due to the electrolytic action of the copper against the steel barrel. Metal fouling can also result from a rough bore at any velocity.

Micrometer

A measuring instrument with a fine screw adjustment for measuring very small distances. Usually calibrated to read in increments of 0.001" or 0.0001".

Mid-range Trajectory (MRT)

The highest vertical distance of a bullet above the line of sight at a point approximately halfway from muzzle to target or point of aim. The MRT is varies with the zero range for a given load. Also called the maximum ordinate.

Minute-of-angle (MOA)

A unit of angular measurement equal to 1/60th of a degree. Although usually approximated as one inch per 100 yards, it is actually equal to 1.047" per 100 yards.

Misfire

Complete failure of a cartridge to discharge after the primer is struck by the firing pin.

Moderator

A device designed to reduce muzzle report on an airgun by moderating the air released when firing.

Mould Blocks

Two "mirror twin" pieces of metal having a bullet-shaped cavity in which lead bullets are cast from molten lead.

Mushroom

The ability or capacity of a bullet to increase its diameter upon impact with animal tissue. The name comes from the desired shape after expansion.

Muzzle

The front end of a barrel. The point at which a projectile leaves the barrel.

Muzzle Blast

The compression of air caused by hot, high-pressure powder gases jetting from the muzzle of a gun.

Muzzle Brake

A deflector fitted to a gun muzzle to deflect exiting gases. Usually used to reduce recoil by redirecting the jet effect of muzzle blast. Also called a recoil compensator, or comp for short.

Muzzle Energy (ME)

The energy of a bullet at the muzzle. At this point a bullet's energy is highest. See energy.

Muzzle Pressure

Gas pressure in the barrel at the muzzle at the instant the bullet leaves the muzzle.

Muzzle Velocity (MV)

See velocity.

NBRSA

National Bench Rest Shooters Association.

Neck 

The portion of a cartridge case that grips the bullet. In a bottlenecked case, the cylindrical portion of the case in front of the shoulder.

Neck Down or Up  

To change the diameter of the case neck during case forming.

Neck Expansion      

The act of expanding a sized case neck by pulling it over an expander plug or button.

Neck Ream  

Reducing neck wall thickness from the inside with a reamer. Commonly performed when forming a short case from a much longer one, such as the 300 H&H to 6.5mm Remington Magnum conversion.

Neck Size 

To resize part or all of the neck only, leaving the case body unchanged.

Neck Turn 

Reducing neck wall thickness from the outside by cutting or grinding.

Non-corrosive

Cartridges or primers with priming mixture that does not contain any compound capable of causing rusting or corrosion of bore or adjacent parts. All commercial small arms primers made in the U.S. and most military ammunition produced since 1954 has non-corrosive primers, although it is well to clean the bore promptly when in doubt.

Non-mercuric

A priming mixture containing no mercury compounds.

NRA

National Rifle Association.

NRMA

National Reloading Manufacturers' Association.

NSSF  

National Shooting Sports Foundation.

Ogive

The curved portion of a bullet ahead of the cylindrical, or shank, section. Also, the radius of this curve, usually expressed in calibers.

Oil Dent       

Dent in a cartridge case formed by too much oil or lubricant when sizing. Usually seen on the shoulder of bottleneck cases.

Overbore Capacity

A common but unscientific term referring to a cartridge case that has too much case volume for its bore volume. Technically, every case can be over its bore capacity with some powder. Generally used when a case has a volume so large in relation to the bore diameter that only the very slow burning powders will give satisfactory performance, or very little velocity is gained by adding more powder.

Parallax

In telescopic sights, the condition that exists when the crosshairs do not lie exactly on the image plane. Excessive parallax makes the shooter's eye position very critical if repeatable accuracy is to be obtained. Most lower power scope have the parallax pre-set at 150 yards; high-magnification scopes (10X and up) commonly have an adjustable objective to correct for various distances.

Patched or Paper-patched Bullet

A bullet with a wrapped paper "patch" commonly used in older black powder cartridges. Derived from the even older cloth patch used to wrap a muzzle-loader ball. The patch helped seal the powder gases and reduced bore leading, and was an evolutionary step towards today's metal bullet jackets.

Pattern

The way a shotgun places its shot load. Generally measured as the percentage of pellets that strike in a 30" circle at 40 yards.

Pierced Primer

A primer that has been punctured; caused by a defective firing pin, a weak firing pin spring or excessive clearance between the firing pin and breech.

Plinking

Informal target practice commonly at informal targets. Shooting for fun where no one keeps score.

Pneumatic

Any airgun that uses compressed gas as its powerplant. Examples would be Precharged, Single-Stroke, and Pump-up.

Point of Aim

That point on which a gun's sights are aligned; the intended spot where the shooter wants his bullet to strike.

Port Pressure

In a gas-operated firearm, the pressure measured at the gas port leading to the piston assembly.

Powder 

The propellant material used in most gun systems. Divided into two basic types: smokeless powder and black powder. It is produced in a wide variety of types, forms and brand names intended for specific applications. It varies chiefly according to burning speed. The fast-burning types are used for light bullets in short barrels at low velocities: slower-burning powders are used in longer barrels and in greater quantities to drive the bullet at higher velocities. Most powder contains a major percentage of nitrocellulose, with small traces of other compounds intended to control burning rate or prevent deterioration; such powder is called single-base; smokeless powders containing a percentage of nitroglycerine are called double-base. Powders containing substantial amounts of other organic nitrates are called multi-base. Further identified by shape of individual kernels or granules. See ball powder, flake powder and extruded tubular powder. Black powder is a mechanic