Glossary of Ammunition Industry Definitions

A | B | C | D | E | F | G | H | I | J | K | L | M | N | O | P | R | S | T | V | W | Y | Z 

A

ACP  --  Abbreviation for ‘Automatic Colt Pistol.’

Action  --  The portion of a firearm where the cartridge is loaded, fired, and unloaded.

Aerodynamic Jump  --  The vertical shift a projectile experiences as it encounters crosswind.

Ammunition  --  An assembly of components used to discharge a firearm and propel a projectile down target (bullet, primer, cartridge case, and powder).

Ammunition, Small Arms  --  A military term for ammunition used in firearms with barrel bores no larger than one inch in diameter.

Anneal  --  The process of heating (and softening) metal (brass) to restore ductility (tensile stress) after it has been fired.

Antimony  --  A metal alloy used to harden lead for bullets (approx. 3%).

Anvil  --  The metal point upon which the firing pin drives the explosive compound of the primer, creating an ignition spark.

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B

Ballistics  --  The physical science of projectiles in motion.  Firearms include:  interior ballistics; exterior ballistics; and terminal ballistics.

Ballistic Coefficient  --  The calculated aerodynamics (atmospheric resistance) of a bullet after its been fired and before it reaches target  -- a mathematical index for deceleration of a projectile in flight.

Balloon Head  --  When the primer on a cartridge case extends into the powder chamber – should not be reloaded.

Bearing Surface  --  The surface area of a bullet that makes direct contact with the rifling of a barrel (lands and grooves).

Bedding  --  The material and/or method for fitting a barrel and action to a rifle stock.

Belted Case  --  Any cartridge case (typically rifle) that possesses a raised belt (or band) around its base past the extractor groove to insure positive headspacing for ‘non-shouldered’ magnum cartridges.

Berdan Primer  --  A primer used in most European cartridges (without Anvil).

Black Powder  --  Potassium Nitrate, Charcoal, and Sulphur – typically used in modern muzzle-loading firearms.

Boat Tail  --  The tapered area of a bullet at the base-end (heel) that produces less atmospheric resistance (drag) during flight.

Bore  --  The interior portion of the barrel, forward of the chamber.

Bore Axis (Line of Bore)  --  The invisible line passing through the center of the barrel (infinite aim of barrel).

Bore Capacity  --  The term used to describe the volume of the bore as it relates to its ability to effectively burn a given amount of powder (‘Burn Rate’ effectiveness).

Boxer Primer  --  A primer used in most American cartridges (with Anvil).

Brass  --  A metal alloy comprised of copper and zinc.  The word is used in reference to the cartridge case, as well as a general term for ammunition.

Bridging (Powder Bridging)  --  When a powder measure accumulates in the drop tube, causing uneven loads.

Bullet  --  The projectile shot from a firearm – accuracy is dependent on center of gravity concentric with center of form.

Bullet Pull  --  The amount of force (typically in pounds) necessary to pull a mounted bullet from a cartridge (also, ‘Neck Tension’).

Burn Rate  --  The time it takes, as compared to a known general standard, for powder to burn on ignition.   

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C

Caliber  --  The diameter of a given projectile, either in inches or millimeters.

Cannelure  --  A groove around the cylindrical portion of a bullet into which the edge of the cartridge is crimped.

Cartridge  --  A single unit of complete ammunition for small arms, consisting of bullet, powder, casing and primer (‘Round’).

Case Forming  --  The process of reforming a cartridge case into a usable, pre-specified case dimension for reloading.  The process can be done via press dies and / or fireforming.

Chamber  --  The part of the barrel that accepts the ammunition for firing.

Chamfer  --  The process of removing burrs on the inside of a cartridge case to insure proper bullet seating (also, ‘Deburr’).

Charge  --  The amount of powder loaded into a cartridge case when producing ammunition.

Compressed Charge  --  When the seating of a bullet is compressed into the powder – typical for slow burning powders in large capacity magnums.

Crimp  --  The process of edging-in the mouth of a cartridge case to increase the tension and better secure the bullet.

Crimped Primer  --  When the primer is crimped into the primer pocket – typical for military cases.

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D

Decap  --  The removal of a ‘spent’ primer from a cartridge case.

Dummy  --  A round of ammunition that is inert.

Duplex Load  --  A powder load consisting of two different types to maximize the efficiency of burn rates – typically fast burn rates near primer and slower burn rates for main charge.

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E

Erosion (Throat Erosion)  --  The wearing of parts (usually the throat of the barrel) due to extreme heat and friction commonly caused from hot-burning powders, over-firing and / or large capacity loading.

Expanding Bullet  --  A bullet that is designed to expand on impact, thus creating a more lethal contact with the target – typical types include hollow points and soft points.

Expansion Ratio  --  The calculated ratio of the case volume and bore volume to the case volume alone – denotes powder burning efficiency.

Exterior Ballistics  --  The physical science associated with the flight of a projectile.

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F

Fireform  --  The process of reforming a cartridge case by firing it, thus improving the fit to chamber for a particular firearm.

Firing Pin (Striker)  --  The part of a firearm that the trigger mechanism releases to strike the primer of a cartridge to detonate it.

Flash Hole  --  A hole (or holes) between the primer pocket and the powder chamber of a cartridge case.

Flat Nose  --  A bullet design that possesses a broad, flat meplat  -- typical for tubular magazines that align rounds nose to primer.

FMJ (Full Metal Jacket)  --  A bullet design that encases the softer lead core bullet with a harder, outer metal covering – typically gilding metal.

Fouling Shot  --  An initial shot fired through a clean bore to intentionally leave residue so as to prepare the bore for improved consistency and performance in subsequent shots.

Frangible  --  A bullet designed to disintegrate into small particles upon impact  -- typically used for safety reasons to minimize bullet penetration.

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G

Galling  --  The roughness and degradation of two metals as they rub together due to friction.

Grain  --  A unit of measure defining the weight of a bullet (7,000 grains per 1 lb.).

Gilding Metal  --  A metal alloy (approx. 90% copper, 10% zinc) used for ‘jacketing’ bullets.

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H

Half-Jacket  --  A swaged lead bullet that has a jacket covering half of the bullet with the remainder of lead exposed.

Hangfire  --  A delay in time between the striking of the firing pin and the ignition of cartridge.

Head Separation  --  A circumferential cracking of the cartridge case – typically caused by excessive headspace during firing.

Headspace  --  The distance measured from the part of the chamber that stops forward motion of the cartridge to the face of the bolt.

Headstamp  --  The designated markings on the head of a cartridge case that designate the manufacturer, caliber, and / or date of manufacturer.

Heel  --  The portion of a bullet that’s between the main body and the base (the edge of the bullet’s base).

High Primer  --  A primer that is seated above the head of the cartridge case (non-flush) – a defect that makes the cartridge dangerous as it becomes susceptible to ‘slam fires’ during autoloading, etc.

Hold Over  --  The distance a shooter must raise his point of aim to be on target when zeroed-in at a lesser distance.

Hollow Point  --  A type of bullet that possesses an opening in the nose, thus allowing the projectile to expand upon impact.  

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I

Ignition Time  --  The time span it takes between the firing pin ignition of the primer and the pressure increase to move the bullet from its seat within the cartridge case.

Improved  --  The term used for a cartridge that has been fireformed and now possesses a contoured shape for improved headspacing.

Ingalls’ Tables  --  Ballistic tables computed by Col. James Ingalls of the US Army – calculates velocities and trajectories for small arms projectiles.

Interior Ballistics  --  The physical science associated with the events of a projectile as it moves through the interior (chamber / barrel) of a firearm.

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J

Jacket  --  An outside metal cover that encloses the soft lead core of a bullet (a metal sheath).

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K

Keyhole (Keyholing)  --  Refers to an elongated hole left in a target by a projectile that is not traveling point-on, thus indicating a ballistics stability problem.

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L

Lands  --  The internal bore dimensions above the grooves in a rifled barrel.

Leade (‘Freebore’)  --  The unrifled area of the barrel bore immediately in front of the chamber.

Leading  --  A build-up or accumulation of lead in a barrel of a firearm due to cast or swaged bullets – typically lessens accuracy to a substantial degree.

Line of Elevation  --  The angle represented from the ground (zero degrees) to the Axis of the Bore.

Line of Sight (LOS)  --  The invisible line from the firearm sights (or optics) and the target (what the shooter sees).

Load Density  --  The percentage of the powder load (volume) to the powder chamber (volume) of the cartridge case.

Lock Time  --  The amount of time (milliseconds) between pulling the trigger and ignition of the powder in the cartridge.


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M

Magnum  --  A cartridge designed with greater powder capacity than its earlier standard.

Match Grade  --  The manufactured quality that is suitable for a competitive match – typically with specifications that possess tighter tolerances and meet better accuracy.

Maximum Ordinate  --  The maximum height a projectile travels (above the Line of Sight) on its path to impact.

Mean Radius  --  The average radius of a group of shots from the center of the group.

Meplat  --  The diameter of the flattened tip of the nose of a bullet.

Misfire  --  When a cartridge fails to fire after being struck by firing pin.

MOA (Minute of Angle)  --  The measured angle equal to 1/60th of a degree, or approximately one inch at 100 yards (1.0472”).

Muzzle  --  The end of the barrel.

Muzzle Energy  --  The kinetic energy associated with a projectile as it leaves the muzzle of a firearm.

Muzzle Pressure  --  The pressure remaining in the barrel after the projectile leaves the muzzle.

Muzzle Velocity  --  The speed that a projectile is traveling when it leaves the muzzle of a firearm.

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N

Neck  --  The portion of the cartridge case between the main body and the mouth of the case – typically funnel shaped.

Necking Down or Necking Up  --  The process of resizing the neck (shrinking or expanding) of an existing cartridge case to fit the bullet of a different caliber.

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O

Obturation  --  The process of sealing the chamber and bore through pressure.

Ogive  --  The pointed, curved surface (the arc) that forms the nose of a bullet, thus creating the aerodynamics to reduce atmospheric resistance (drag).

Overbore Capacity  --  When a cartridge contains more powder than can be burned for the bore diameter and volume.


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P

Penetration  --  The ability of a projectile to enter a target’s mass based on its delivered kinetic energy – typically measured in inches via ‘Impact Depth.’

Pierced Primer  --  A primer which is pierced by the firing pin – typically due to excessive high pressures.

Point Of Impact (POI)  --  The point at which a projectile strikes it’s target in relation to the point where the shooter is aiming.

Popped Primer (Protruding Primer)  --  An outward displacement of the primer after firing – typically due to excessive headspace in conjunction with a light load.

Pressure  --  The force exerted from the expanding gas generated by the combustion of the powder – measured in pounds per square inch (PSI).

Primer  --  The ignition component that sparks the powder.

Primer Leak  --  When gas escapes between the primer and the primer pocket due to excess pressure.

Primer Pocket  --  The cavity at the base of a cartridge case that holds the primer.

Primer Pocket Reaming (Swaging)  --  Removing the crimp in a primer pocket.

Proof  --  Testing a firearm’s ability to withstand working (and excess) pressures and strains (determining ‘extra’ strength and safety margins for a firearm).

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R

Remaining Velocity  --  A projectile’s velocity (feet per second) at a given range of fire.

Resizing  --  The process of returning a fired cartridge case back to dimensions in which it can be rechambered and re-fired – typically through the use of a resizing die.

Reticle  --  The system of aiming as found in firearm optics (crosshairs, lines, dots, etc.).

Rifling  --  The process of cutting (or forming) spiral grooves into the bore of a barrel, thus creating a spin to the fired projectile.

Round Nose  --  A type of bullet possessing a blunt, round profile.

Rimmed Case  --  A cartridge case with a flange on its base – used for extraction and a means for headspacing.

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S

Sabot  --  A designed cover (sheath) that allows a smaller bullet to be used in a larger bore barrel.

SAAMI  --  Sporting Arms and Ammunition Manufacturers Institute.

Seating  --  The placement of a bullet within a cartridge case.

Secant Ogive  --  A bullet with a design whereby the cylindrical surface is secant to the curve of the head.

Shoulder  --  The portion of a cartridge case located between the neck and the body.

Slam Fire  --  When a firearm discharges during chambering.

Soft Point  --  Any jacketed bullet with an exposed lead tip.

Spire Point  --  A cone-shaped bullet, as opposed to an arch-shaped (ogival) bullet.

Squib Load  --  A firearm malfunction whereby the projectile remains lodged within the barrel – typically due to low pressure firing.

Swage  --  The process of forming metal under pressure – typically with a die or punch.


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T

Tangent Ogive  --  A bullet with a design whereby the cylindrical surface is tangent to the curve of the head.

Terminal Ballistics  --  The physical science associated with a projectile’s impact on a given target.

Time Of Flight  --  The time it takes for a projectile to reach a given distance after firing.

Throat  --  The unrifled portion of a barrel that’s located between the chamber and the rifled portion of the barrel (‘Freebore’).

Trajectory  --  The arced (or parabolic) path a projectile takes during flight.

Twist Rate  --  The distance (inches) a projectile travels during a single rotation as created by the barrel’s rifling (ex. 1:10 T = one revolution in 10” as it leaves the muzzle).

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V

Velocity  --  The speed of a projectile – typically expressed as feet-per-second (FPS).


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W

Wadcutter  --  A bullet designed for paper targets – typically with a flat nose (or near flat) in order to leave a clean hole for easy scoring.

Web  --  The part of a cartridge case between the primer pocket and the powder chamber where the flash hole is located.

Wildcat  --  A custom cartridge that is not mass produced – typically made to optimize a specific performance characteristic.

Windage  --  The lateral (side-to-side) adjustment for firearm sights – compensation for wind drift.

Wind Deflection  --  The lateral (side-to-side) effect on a bullet in flight caused by crosswind.

Work Hardened  --  The eventual brittleness of a cartridge case due to repeated stress on the metal caused from repeated firing and reloading – typically around the neck of the case resulting in cracking and splitting.

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Y

Yaw  --  The directional drifting (‘Drift’) of an in-flight projectile due to the spinning of the projectile.

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Z

Zero Point (Zero or Far Zero)  --  Where the point of aim and the point of impact coincide.

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