Calibre (or caliber) - 1. A term used to designate the specific cartridge(s) for which a firearm is chambered. 2. Firearms: The approximate diameter of the circle formed by the tops of the lands of a rifled barrel. 3. Ammunition: A numerical term included in a cartridge name to indicate a rough approximation of the bullet diameter. (abbr. cal). Proper style for calibre designations is no decimal point. (examples: 270, 30-06, 22, 357 Magnum)

Cannelure - Groove or grooves around the circumference of a bullet, into which the case mouth can be crimped.  These grooves, usually one to a bullet, provide the best means of securely crimping the case mouth into the bullet.

Cap - 1. An obsolete term referring to a primer. 2. Muzzle loading, as in cap-and-ball. (See percussion cap).

Carbine - A rifle of short length and light weight originally designed for mounted troops. It can also be chambered for handgun calibres.

Cartridge - Complete unit of ammunition, comprising cartridge case, bullet, powder and primer.  ( Click here for picture. )

Cartridge Conversion - Converting cartridge cases of one calibre or design to another. See annealing, neck down/up.

Case - Hollow brass container housing the propellant of a cartridge, the neck of which grips the bullet, and the head of which accepts the primer. ( Click here for picture. )

Case Forming - See Cartridge Conversion.

Case Neck Brush - The metal brush and handle used to clean the inside of case necks.

Case Trimmer - A device used to remove excess material from a case mouth.  Metallic cases stretch after extensive reloading and firing because the brass flows forward.  These cases must be trimmed back to at least the maximum case length.

Case Trimmer Pilot - The pilot guides the cutting portion of a case trimmer by fitting inside the neck of the case to be trimmed.

Case Trimming - Shortening cartridge cases to specified length after resizing/firing has stretched them. This is done to ensure uniform grip on the bullet, and thus better accuracy.

Cast - Cast is the lateral displacement of the centreline of the buttplate (pad) from the centreline of the bore. For a right-handed shooter, when the centreline of the buttplate is to the left of the bore, it is expressed as cast-on and to the right as cast-off. The opposite is true for left-handed shooters.

Cast Bullet - Lead alloy bullet cast from a mould, as distinct from a jacketed (extruded/swaged) or lathe-turned bullet.

Casting - The act of forming an object, such as a bullet, by pouring molten material into a mould.

Cast-off - Offset of the butt of a gun to the right for a right-handed shooter. Theoretically better aligns shooter's eye with the bore.

Cast-on - Offset of the butt of a gun to the left for a left-handed shooter. See cast-off.

Centerfire (CF) - Cartridge with a component primer situated in the centre of the case head, as distinct from a rimfire cartridge.

Chamber - 1. In a rifle, shotgun or pistol, the cavity at the breech end of the barrel bore that has been formed to accept and support a specific cartridge or shell.
                   2. In a revolver, the holes in the cylinder that have been formed to accept a specific cartridge.

Chamber Pressure - Pressure generated by expanding gases inside the cartridge chamber upon firing.  Varies between calibres, and depends on powder type, powder charge, bullet weight, etc.  All firearms are built to withstand pressures up to specified limits which, for safety's sake must not be exceeded by handloaders.  Normally measured in pounds per square inch.

Chamfer - To ream a taper on the inside of a case mouth, especially after case trimming has taken place.

Charge - Amount of powder used in loading a cartridge. Selected for a specific bullet configuration ( i.e. manufacturer, shape and weight ) to give optimal performance.  It is very important for handloaders to note that, should ANY component be changed, the charge must be reduced, and worked up again.  Also refers to the amount of shot used in a shotshell.

Checkering - A diamond-like pattern in the wood, plastic or metal components of a firearm for ornamentation or improved gripping.

Cheekpiece - A raised part of the side of the stock of a shoulder-arm against which the shooter rests his face. Usually associated with a Monte Carlo-type stock. Its purpose is to raise the shooter's eye to the height necessary to maintain the triangle of force.

Choke - An interior constriction at or near the muzzle end of a shotgun barrel for the purpose of controlling shot dispersion.

Choke Tubes - Interchangeable muzzle constrictions. See choke.

Chronograph - Electronic instrument used for measuring the velocity of a bullet. An important part of a handloader's equipment as it helps to determine consistency of loads.

Clandestine Operation - An activity to accomplish intelligence gathering, counter-intelligence, or other similar activities sponsored or conducted by governmental departments or agencies in such a way as to assure secrecy or concealment of the operation. It differs from covert operations in that the emphasis is placed on the concealment of the operation, rather than on the concealment of the sponsor's identity.

Clip - A strip of metal to hold cartridges or shells in proper sequence for feeding into a specific firearm, usually by way of gripping the rim to the rear of the case. Sometimes also used, wrongly, as alternative for Magazine.

Cold-Bore Shot - The first shot from a clean, unfired weapon.

Collimator - Device used in roughly sighting in telescopic sight without firing a shot. It comes with a pin for every calibre it is to be used for. The pin is inserted in the barrel to keep the collimator aligned with the bore, and then the scope is set in such a way that the cross-hairs/reticle are aligned with that of the collimator. The scope will then be roughly set for 100 metres.

Combination Gun - A multiple barrel firearm designed to handle different sizes or types of ammunition.

Compensator - A device attached to the muzzle end of the barrel that utilizes propelling gases to reduce recoil.

Components - Any of the various parts which go into the making of a cartridge.

Compressed Load - Powder charge sufficiently voluminous to be compressed by the bullet when seated in the case. Even though it is not a problem, overly compressed loads can change the characteristics of the charge.

Concealment - Protection from view. This is not necessarily the same as cover. Cover provides concealment, but concealment does not always provide cover.

Conditions - The state of the weapon. Normally associated with the firearm's state in a defensive carry mode. The conditions are defined as follows:
Condition 1:   Full magazine, round chambered, hammer cocked, safety on
Condition 2:   Full magazine, round chambered, hammer down, safety off
Condition 3:   Full magazine, chamber empty
Condition 4:   Full magazine separate from weapon, chamber empty

Controlled Expansion - Describes characteristics of bullets designed to expand at a controlled rate in a target. Such designs may have jacket walls that get progressively thicker towards the rear, or features which inhibit expansion midway. Purpose is to afford optimum penetration and weight retention, thus maximum effect on the target.

Cook-off - A situation where the round in the chamber fires from the heat of the chamber after prolonged shooting.  This is why the CETME rifle fires full-auto from an open bolt.

Cordite - Early smokeless rifle propellant in the form of long “cords” rather like uncooked spaghetti. Most Eley-Kynoch (British made) rifle cartridges were loaded with cordite, which had a very high burning temperature, causing rapid barrel erosion.

Cordite Ear - Slang for permanent partial deafness in shooters - the result of not using adequate ear protection.

Core - Lead, less often tungsten, interior of a jacketed bullet.  It makes up the bulk of the bullet's mass and size.  Its high specific gravity and malleability serve to fulfil different functions:
i)  It gives the bullet its mass-to-size ratio to improve momentum.
ii)  On impact, the malleable lead core in an expanding bullet also has the ability to deform after impact, splitting the surrounding jacket without it breaking apart.
iii)  The tungsten core, where used by the military, is used for armour piercing.

Corrosion - The eating away of the bore by rust or chemical reaction.

Corrosive Primers - Primers, usually Berdan type, that have priming compounds containing Potassium Chlorate, producing Potassium Chloride on ignition. Potassium Chloride is as corrosive as Common (table) salt (NaCl). Also see Mercuric primers.

Cover - Protection from hostile gunfire. Cover is a relative term. Cover that is thick enough to stop pistol bullets may not be adequate protection against rifle bullets. This is a crucial fact to keep in mind when selecting cover.

Covert Operation - An operation that is planned and executed as to conceal the identity of, or permit plausible denial by, the sponsor(s). This differs from a clandestine operation in that emphasis is placed on the concealment of the sponsor's identity, rather than on the concealment of the operation.

Cratering - Term describing primer extrusion caused by excessive pressure (usually through overloading). The primer is driven rearwards against the bolt face so hard that the metal is forced into the firing pin hole, forming a raised crater on the primer surface. Any marks on the bolt face is normally also imprinted on the case head.

Crimp - The compressing or turning in of the case mouth, usually into a cannelure (crimping groove) in the bullet's circumference, to provide a firmer grip on the bullet.  The object is to prevent the bullet extruding from the case neck during recoil, or from being shoved deeper into the case by contact with the front wall of the magazine during recoil.  With shotshells the term usually applies to the closure at the case mouth.
Also the crimping of the primer pocket around the primer to seal it.

Crimped Primer - A forcing inward of the brass around the top of the primer pocket.  This is frequently found on military cartridges and is done to prevent set-back of primers.  The crimp must be removed before repriming the case.

Cross Dominance - A soldier with a dominant hand and a dominant eye that are not on the same side; for example, a right-handed firer with a dominant left eye.

Crown - Configuration of exit part of the muzzle.  The barrel is not merely cut off and left with the sharp edges, but the edge from the inside is rounded towards the outside.  The form and angle of this has an influence on accuracy and stability of the bullet. The concentricity of the crown is very important, as variations will negatively influence the bullet as it exits the muzzle.  The rifling at the end of the barrel can be slightly relieved, or recessed. The purpose is to protect the forward edge of the rifling from damage, which can ruin accuracy.

Cruiser Ready - Firearm (usually a shotgun) stored with chamber empty and several shells in the mag tube.

CUP - Abbreviation for Copper Units of Pressure, a unit of measure for chamber pressure, based on crushing a copper cylinder.

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