Accuracy: The measure of precision in consistently obtaining a desired result. In shooting, the measure of a bullet 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.
Air Resistance: The slowing effect of air on a projectile in flight.
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.
Ball: Early term for “bullet.” 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. Either spherical or flattened spherical shape.
Ballistics: The science of projectiles in motion. Divided into three categories: 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.
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 high BC will overcome air resistance better than one with a low BC.
Battery Cup: Type of primer in which anvil and primer cup are supported in an outside cup. Shot shell primers are of this type.
Bearing Surface: That portion of a bullet’s surface that 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 raised band or belt at the base ahead of extractor groove. A variant of the rimless case. Belt acts to control headspace of the cartridge. See rim and rimless.
Berdan: Type of primer common outside the US with no integral anvil. Anvil is formed in bottom of primer pocket in the case. Named after the inventor, Col. Hiram Berdan, an American.
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.
Black Powder: The oldest ballistic propellant for muzzleloaders and early cartridge arms composed of a mixture of potassium nitrate (saltpeter), charcoal and sulfur.
Boat Tail: Name given to a bullet type with tapered base. Also called “tapered heel,” the design reduces aerodynamic drag on the bullet by smoothing the airflow over the base.
Body (of a case): That section of a 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.
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 and/or case neck tension.
Bullet Puller: A tool for extracting bullets from loaded centrefire cartridges. The inertial and collet types are most common. Used to correct loading errors or salvage components from ammunition that is unsuitable for firing.
Burning Rate: A relative term used to rank the rapidity with which a given powder releases energy in comparison with other powders. Typically based on heat generation in a lab device called a calorimeter bomb. In a real-world gun system, burning rates may vary depending on factors such as case size, pressure range, expansion ratio, and others.
Calibre: A term derived from Arabic qalib, meaning “mould” or “form,” first applied to the weight of a bullet and then to the diameter. Calibre now refers specifically to the diameter of either a projectile or the bore of a gun. It is the approximate 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! Also used in naval artillery as a measure of bore length compared to the diameter (or caliber) of a specified gun. A “five-inch, fifty-four caliber” naval rifle would have a barrel 270 inches or 22.5 feet long.
Cannelure: Circumferential groove(s) around a bullet or cartridge case. Used for identification, to hold lubricant, or to crimp case into.
Canister Powder: Since hand loaders do not have the laboratory facilities needed to determine the loading characteristics of a powder, powder manufacturers have developed a rigid set of specifications for each hand loader powder they sell. Each lot of powder is made or blended to meet these specifications so the hand loader will always have uniform results. Powder made to these specifications is termed “canister” grade since it is usually packed in canisters of appropriate size for consumer use. Commercial ammunition manufacturers that have laboratory facilities can use the “bulk” grades, which may vary enough from lot to lot to be dangerous to hand loaders. Loads are adjusted for each powder lot as required by test results.
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 occasionally to shot shells.
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 Trimming: Shortening an overly long case by removing metal at the case mouth.
Cast Bullet: Bullets for rifles or pistols formed from molten lead or lead alloy in a mould. See mould blocks.
Center Fire (CF): Refers to centrally located primer in base of metallic cartridges. Also called centre fire. Most centre fire cartridges are reloadable.
Chamber: That part of the bore, at the breech, formed to accept, support, and confine the cartridge. In a revolver, chambers are located in the cylinder.
Chamber Cast: A casting, usually of molten sulfur or low melting-point metal poured in the chamber, to assess chamber shape, dimensions, 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 shot shell.
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 align the sights with the bore of a rifle or handgun.
Combustion: Burning; in firearms, the chemical process which unites oxygen and other substances in gunpowder to release energy in the form of 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.
Compressed Charge: A charge of powder that is compressed by the bullet during seating in the case.
Components: The parts that go into the making of a cartridge.
Copper Crusher: Small, solid copper cylinder used in a pressure gun to measure chamber pressure. See pressure gun.
Core: The interior part of a jacketed bullet; usually a lead alloy in sporting ammunition.
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.
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. See below. Cartridge cases can also be corroded by salts or acids.
Corrosive Primer: A primer whose burnt residue is hygroscopic (attracts moisture) and usually containing slats of chlorine. The residue will rapidly rust a bore unless removed. All component primers in the US 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 shot shell case. Two types are used. A roll crimp is the bending or folding 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 folding the case mouth.
Crimped Primer: A forcing inward of the brass around the top of the primer pocket to prevent setback 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—priming 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.
Damascus barrels: Barrel tubes built up by twisting alternate strips of iron and steel around a fixed rod (mandrel) and forge-welding them together in varying combinations according to the intended quality and the skill of the maker. The rod was withdrawn, the interior reamed and the exterior draw-filed until the finished tube was achieved. Damascus barrels may be recognized by any of a variety of twist or spiral patterns visible in the surface of the steel. Generally unsafe to use with modern smokeless powders – check with a gunsmith first before using.
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 over powder kernels to control the burning characteristics of the base powder. Aptly described as a “temporary fire-proofing” of a powder kernel.
Die: In hand loading, a tool to form or reform cases or bullets, or to seat bullets.
Double-base Powder: Nitrocellulose (smokeless) propellant that uses nitroglycerin as the plastisizer.
Drag: See air resistance.
Dram Equivalent: In shot shells, 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 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. Must be corrected for difference between line of sight and line of departure. Drop is normally reported assuming a horizontal barrel.
Duplex Load: Use of two different powders in loading the same cartridge. There is little or no advantage to duplex loading in small arms and results are unpredictable and usually dangerous.
Elevation: The vertical adjustment of a sight to bring the point of aim to coincide with the 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 combined with the action of hot powder gases.
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 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 rather than a pressure sign.
Extrusion: The shaping process used in the manufacture of bullet jackets and cores.
Extruded Tubular Powder: Another term for cylindrical powder. Formed by forcing damp propellant mix through a die during manufacture and cutting to desired lengths. May have one or more longitudinal holes through the grains.
Fire form: 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 vertically lift one pound a distance of one foot against the force of gravity.
Forcing Cone: The slope of the forward end of the chamber of a rifle or shotgun that decreases the chamber diameter to bore diameter.
Form Factor: A multiplier that relates the shape of a bullet to the shape of the standard 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, that a bullet travels upon firing before it contacts the rear portion or origin of the rifling.
Frontal Ignition: Experimental type of cartridge where primer flash is directed to the forward part of the powder charge through a metal tube.
Galling: Effect of friction between a cartridge 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 energy 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.
Gilding Metal: A copper-zinc alloy used for bullet jackets, consisting of 5 parts zinc and 95 parts copper. Commercial bronze (10 parts zinc to 90 parts copper) is informally referred to as gilding metal when used for bullet jackets.
Grain: In English weight measure, 7000 grains equal one pound; 437.5 grains equal one ounce. Incorrectly used in referring to a particle, or kernel, of powder. Thus “35 grains of powder” always refers to 35 of the weight-unit grains, never to 35 individual kernels of powder.
Grand Slam: An honorary award to a hunter who has collected the four varieties of North American wild sheep. Also the registered 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 shots 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.
Half-jacket: A short 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.
Hang fire: 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 seconds. 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. In hand loading, the combination of cartridge case and gun must be considered when talking of headspace. To a hand loader, few guns need to have excessive headspace, since he can adjust the cartridge case to fit the chamber, even though the chamber may have excessive headspace when measured by SAAMI standards.
Heel: The edge of the bullet base.
Holdover: The distance above target a shooter must “hold over” to hit at ranges greater than the gun’s “zero.” See zero.
Hollow Point (HP): Bullet design feature; an axial hole at the point of the bullet.
HOT-COR: The registered 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 setting on fire of the propellant powder charge by the primer.
IHMSA: International Handgun Metallic Silhouette Association.
Improved: Term used to indicate a standard cartridge case that has been altered by fire forming 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 US.
IPSC: International Practical Shooting Confederation.
Jacket: The cover or “skin” of a bullet. Usually made of gilding metal in the US, but copper-clad steel and mild steel are also used in other countries. See cupro-nickel and half-jacket.
Keyhole: The 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 bore 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 US
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 line at which a bullet leaves the muzzle of a firearm, equivalent to the axis of the bore. The bullet immediately falls away from this imaginary line.
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.
Locking Lugs: Usually used in reference to rotary bolt-action firearms. Protrusions on the bolt that 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.
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.
Lubricator-Sizer: A tool used to size and lubricate cast lead bullets. Often contracted to lubrisizer.
Magnum: Originally, a large wine bottle holding approximately 2/5 of a gallon. In shooting, it refers to a cartridge of exceptional size or power. First applied to large bottleneck cartridge, hence the name. Magnum is now more of a marketing term than a technical one.
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 diameter of 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): Usually refers to 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 horizontal distance, 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.
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 pressure effect of powder gases jetting from the muzzle of a firearm.
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. See compensator.
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.
Neck: That portion of a cartridge case that grips the bullet. In a bottlenecked case, that portion of the case in front of the shoulder.
Neck Down or Up: To change the diameter of the case neck during case forming to accept a larger or smaller diameter bullet.
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, more rarely, 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 US 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.
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 cartridge case formed by too much oil or lubricant when sizing. Usually seen on or near the shoulder.
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.
Parallax: In telescopic sights, the condition that exists when the reticle (crosshairs) does 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 scopes have the parallax correction 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.
Point of Aim: That point on which a gun’s sights are aligned so as to allow the bullet to strike the desired point of impact.
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 nitroglycerin are called double-base. Powders containing substantial amounts of other organic nitrates are called mullet-base. Further identified by shape of individual kernels or granules. See ball powder, flake powder and extruded tubular powder. Black powder is a mechanical mixture of sulfur, charcoal, and saltpeter. It is now used primarily in muzzle-loading guns.
Powder Bridging: A “log jam” of powder that may occur in the drop tube of a powder measure. The powder kernels interlock and wedge together to block free passage. Most common with long, cylindrical powder kernels.
Powder Measure: A mechanical device to meter powder charges by volume. Used to speed the charging process, measures must be adjusted initially with an accurate scale.
Powder Scale: A sensitive measuring device used to accurately weigh small charges of powder. Designed expressly for cartridge reloading, it is usually graduated to permit weighing to units as small as 1/10th grain.
Powder Trickler: A mechanical accessory that dribbles a few powder granules at a time, used with a powder scale.
Pressure: The pressure exerted by a burning charge of powder in the chamber of a gun. Expressed normally as the peak pressure in pounds per square inch (psi) or copper units of pressure (cup) depending on the test equipment.
Pressure Gun: Device for measuring radial chamber pressure generated by a cartridge. Usually of the “crusher” type or of the electronic “transducer” type. Both types were used in the development of the Speer Reloading Manual.
Pressure-Velocity Ratio: Numerical comparison of velocity to pressure in a specific cartridge with given bullet and powder.
Primer: Also called “cap”, deriving from the percussion caps used with some muzzle-loading arms. In a centre-fire cartridge, the small metal cup contains a detonating mixture that is used to ignite the propellant powder. The primer is seated in the primer pocket in the base of the cartridge case. The standard American type of primer, the “Boxer,” also contains an anvil. Electrically fired primers are used in some military weapons and in some experimental sporting arms. In a rim-fire cartridge the priming mixture is contained within the rim of the case. See anvil, berdan, boxer, and battery cup.
Primer Flipper: A two-piece metal or plastic tray for orienting and turning primers. Facilitates loading of primer tubes in semi-automated equipment. Primer Indent: Depression made in primer by firing pin. Also called the firing pin impression.
Primer Leak: High-pressure gas escaping between the primer and primer pocket wall. Usually indicates a damaged primer pocket.
Primer Pocket: The vented cavity in the base of a centre-fire cartridge case made to receive and support the primer.
Primer Pocket Reaming or Swaging: Two methods for removing the primer pocket crimp from military cases. Reaming removes metal and swaging moves metal aside.
Primer Punch: A loading tool part that inserts the primer.
Primer Tool: A specialized tool that does only the priming operation. Usually used in reference to off-press priming.
Progressive: Characteristic of a powder that burns at a predictable rate compared to black powder, producing a relatively slow pressure build-up.
Projectile: A bullet or any other object projected by force and continuing in motion by its own inertia. Note: A bullet is not a projectile until it is in motion.
Proof Cartridge: A special cartridge used to test a new or repaired firearm for strength and safety. Usually about 25% higher pressure than normal maximum pressure. Not commercially available.
Propellant: The technically correct term for ballistic chemicals used to propel a projectile. See powder.
Protruding Primer: a) A fired primer that partially backs out of the primer pocket on firing. Usually an indication of low firing pressure. b) Any primer that is not fully seated below the case head.
Pyrodex®: A recently developed black powder replacement designed primarily for use in percussion muzzle loading arms, black powder cartridges and muzzle loading cannon. Manufactured and distributed exclusively by Hodgdon Powder Company.
Ram: The main plunger or shaft of a metallic ammunition-reloading tool.
1. A place where shooting is conducted.
2. The horizontal distance of travel of a projectile from gun to target.
Ream: To remove metal from a cavity with a rotary cutting tool.
Rebated Rim: In cartridge case design, a case whose rim is smaller than its body. Examples: 284 Winchester and 41 Action Express.
Recoil: The backward thrust or “kick” of a gun caused by the powder gases pushing the bullet through the bore and the jet effect of the gases themselves.
Recoil Buffer: A cushioning device to help reduce action battering; most commonly used to limit bolt travel in semi-automatic firearms.
Reloading Press: A tool used in reloading ammunition. Usually has some form of mechanical advantage to reduce effort in resizing or reforming cases. Hold components in precise alignment. Available in several basic types known by the shape of letters of the alphabet; “O” types are most common today, but “H” and “C” types have also been used.
Remaining Energy: The residual or “down-range” energy of a projectile, measured in foot-pounds, at a given distance from the muzzle.
Remaining Velocity: The residual speed of a projectile at a given point on its trajectory.
Reticle: The aiming indicator at the focus of a telescopic sight. May consist of straight or tapered lines (crosshairs), dots, posts, or some combination thereof. Some scopes have auxiliary marks for range estimation.
Rifling: Spiral grooves cut or impressed into the bore of rifles and pistols in order to make the bullets spin, insuring stable flight to the target. See grooves and lands.
Rim: The feature at the base of most cartridge cases in which the extractor engages to pull a fired cartridge from the chamber. In England this is called the flange. See rimless and rimmed.
Rim-fire (RF): Cartridges that contain the priming mixture within the rim. This type is not reloadable under any practical conditions.
Rimless: A case head type; actually a misnomer. Rimless cases have a rim, but it is the same diameter as the case body so it does not protrude.
Rimmed: A case head type whose rim protrudes beyond the case body. Example: 30-30 Winchester.
Round: A military term meaning one complete cartridge. Round Nose: Bullet design feature; a blunt, spherical nose shape.
Rupture: Also separation. In shooting, a failure or break in the wall of a cartridge case, usually allowing gas to escape.
SAAMI: Small Arms and Ammunition Manufacturers Institute. The organization that establishes firearms standards in the United States.
Sabot: From French for “shoe.” In modern small arms usage, a lightweight carrier or “shoe” in which a sub-caliber projectile is centered to permit firing the bullet in a larger caliber barrel. Sabots are usually the discarding type; they fall away from the bullet soon after exiting the gun barrel. Pronounced “say-bo.”
Seating Depth: In a loaded cartridge, the depth to which the base of the bullet is seated below the case mouth.
Sectional Density: A bullet’s weight in pounds divided by the square of its diameter in inches.
Shank: The cylindrical section of a bullet below the ogive. The shank usually defines the bearing surface, that is, the portion of the bullet that contacts the barrel.
Shell Holder: The part of a reloading press that holds the head of the cartridge case on the ram permitting insertion and withdrawal of the case from the loading dies.
Shock: See hydrostatic shock.
Shock Wave: The compression wave formed whenever the speed of a projectile relative to air or other medium exceeds that at which the medium can transmit sound.
Shot: Lead alloy spheres, sometimes copper or nickel-plated, used for the projectiles in shotguns. Chilled shot is hardened. Drop shot is very soft.
Shoulder: The sloping or rounded part of a bottleneck cartridge case between the neck and the body.
Sighting in: Firing a rifle or pistol to determine its point of impact at a specified range and adjusting the sights so the point of impact has the desired location with regard to the point of aim.
Single-base Powder: Nitrocellulose powder made without the addition of any other highly nitrated chemical such as nitroglycerin. See double base powder.
Sizing: Also resizing. Reducing a fired cartridge case to dimensions that allow easy chambering in a firearm of the appropriate caliber. May be full length, partial, or neck sizing. Cast lead bullets are also sized or reduced in diameter by forcing through a die.
Slug: A large, single projectile, often bearing external pre-cut rifling, intended for adapting shotguns to the hunting of larger game such as deer. Also a slang term for bullet. As a verb, “to slug” means forcing a soft lead slug through the bore of a gun and measuring it to determine barrel dimensions.
Smokeless Powder: A nitrocellulose-based propellant. Leaves a non-corrosive residue, but normally produce small amounts of smoke. Named because smoke production is very small compared to the older black powder.
Soft point (SP): Bullet design feature in which a portion of the lead alloy core is exposed at the tip of a jacketed bullet to permit the bullet to increase its diameter upon impact with tissue.
Spent: In shooting, a cartridge or component thereof that has been fired.
Spherical Powder: A registered trademark of Hodgdon Powder Company use to describe round or semi-round grained powders. See ball powder.
Spin: The rapid rotation of the projectile caused by the spiral rifling of the bore. At the muzzle of a high-velocity rifle, spin can be in excess of 300,000 revolutions per minute.
Spire Point: A conical pointed bullet. The line from the shank to the point is nearly straight.
Spitzer: Bullet design feature from German for “point”. A bullet with a pointed nose. The line from the shank to the tip is arched. Compare to spire point above.
Stabilize: To spin a projectile around its long axis rapidly enough to keep it point-on in flight.
Swage: To form by forcing into or through a die. Rhymes with “age.”
Throat: That area of the bore immediately ahead of the chamber tapering to the point where the rifling starts. See also leade or freebore.
Time of Flight (TOF): The elapsed time, in seconds, of a bullet’s flight from muzzle to a given point down-range.
Trajectory: The path of the projectile in flight relative to the line of sight.
Transducer: In ammunition research, a piezoelectric device made of quartz that develops a voltage directly proportional to the pressure applied to it. Used to measure chamber pressures.
Twist: The rate or angle of the rifling in relation to the axis of the bore. Usually measured by the length of barrel required to rotate a bullet one complete turn.
1. The tendency for a bullet to become more cylindrical on firing due to inertia. Also known as slugging.
2. The expansion on impact of a hunting bullet. See mushroom.
Varmint: A variation of “vermin.” A wild animal or bird considered a pest, usually not covered by game regulations.
Velocity: The speed of a projectile. Usually measured in feet per second (fps) at a given range.
Vernier Caliper: A simple slide-type precision measuring tool used by hand loaders. “Vernier” refers to the readout mechanism. The dial-type and electronic digital caliper are becoming more popular because they permit faster and less error-prone readings
Wad: A disc of paper, felt, cork, plastic or other material used primarily in shot shells to separate powder from shot. Can be over-powder, filler, cushion or a combination of these. Speer shot capsules for handguns feature a wad to seal the bore.
Wadcutter: A cylindrical, sharp-shouldered handgun bullet designed to cut a clean round hole in a paper target for maximum score in competition.
WCF: Winchester Center Fire. A proprietary name applied to several cartridges developed by Winchester
Web: That part of a cartridge case between the bottom of the primer pocket and the interior of the case. The web is pierced by the flash hole.
Wildcat: A cartridge formed by altering an existing commercial case to make a style that is not available from ammunition companies. SAAMI dimensional and pressure standards do not apply to wildcat cartridges.
Windage: The amount of sight correction, left or right, applied to compensate for natural drift and/or wind deflection of a projectile.
Wind Deflection: Lateral change in the path of a projectile due to crosswind effects.
Work-hardening: The change in hardness of metal due to repeated flexing or stress. In reloading, continued sizing of a case can work-harden the metal until cracks appear. See annealing.
1. The process of developing a safe maximum load by starting with a lower powder charge and increasing it in small steps only after firing and checking for signs of pressure at each point along the way.
2. Accuracy testing of known safe loads in a step-wise manner.
Yaw: A situation where a bullet “wobbles” on its axis at a small angle to the line of flight. In yaw, a bullet’s tip is normally on the axis of the path but the base is spiraling around that axis. The spin of the bullet causes it to settle into stable flight with both tip and base on the same path axis, usually within 40 to 100 yards for a rifle.
Zero: More correctly, “Zero Sight Adjustment.” That adjustment of a gun’s sights that will place a properly aimed shot at the desired point of impact at some range with a given load, in the absence of wind. The basis from which subsequent sight adjustments are made.
Zero Range: The distance at which the bullet path exactly coincides with the line of sight (LOS). Each gun/load combination actually has two zero ranges—one near the muzzle as the bullet rises through the LOS and another at some greater distance where the bullet descends through the LOS. Normally, it is the second zero range that most shooters need to know.