Cal. or Calibre - System of measurement for the internal bore diameter of a rifled-barreled firearm (rifle or pistol) based on the decimal part of an inch. For example, .25 calibre and .250 calibre both signify a bore size of 1/4 inch. American calibre designations refer to the distance from land to land, not groove to groove. Ammunition companies' marketing departments occasionally take liberties with exact measurements. For example, a .270 Winchester bullet actually measures .277 inch in diameter.
Can - Slang term for a firearm sound suppressor.
Cannelure - A crimped or knurled groove, rolled onto a bullet or the neck of a cartridge case, either to help retain a bullet in its case or to provide a space for bullet lubricant.
Cant - To tilt a gun to one side or the other, complicating sighting considerably. Can cause material loss of accuracy, particularly with a rifle at longer ranges.
Cap - The small cap that contains a detonating charge of fulminate.
Cape Gun - A two-barreled, side-by-side, shoulder-fired gun having one smoothbore shotgun barrel and one rifled barrel.
Captive Ramrod - A rod, for loading and/or cleaning a muzzle-loading firearm (usually a pistol) that is permanently connected to the gun by some sort of swivel, so as to be easily utilized, but never lost. Photo
Carbine - A general term referring to relatively short-barreled, quick-handling rifle.
Cartouche - A mark, typically stamped into the wood, especially of an American military rifle. It shows the initials of the name of the accepting inspector and often, the date he accepted the firearm into service.
Cartridge - In its definition valid from circa 1870 to the present: a small usually cylindrical packet, containing a detonating primer, a powder charge, a load---either a single projectile for a rifle or a quantity of small pellets for a shotgun---and possibly some attendant wadding. The cartridge is placed into the breech of a firearm, comprising all required consumables for the firing of the weapon.
Cartridge Trap - A compartment built into the buttstock of a long gun, usually with a hinged cover, in which are drilled holes deep enough to hold several spare cartridges of the type suitable for use in the specific gun.
Case - A hollow, bottle or drinking glass shaped, piece of metal that is closed on one end except for a small hole which holds a primer. The open end holds the bullet. The hollow portion holds the powder. Together the assembled unit is called a cartridge.
Casehardening Colors - mottled blue/green/brown colors on a shotgun or double rifle receiver, vintage Winchester receiver or Colt Single Action frame. The colors are the by-product of a heat-treating process that incorporates carbon into the surface molecular structure of the steel, providing a hard-wearing surface without making the entire receiver brittle. The parts to be casehardened are packed in a crucible with carbon-rich media such as bone meal and charcoal, heated to bright orange, about 1800įF, then quenched in bubbling oil. Also called Carbonizing.
Cast Off - An offset of a gun stock to the right, so that the line of sight aligns comfortably with the right eye while the butt of the stock rests comfortably on the right shoulder. Almost all right-handed shooters benefit from a little castoff and most custom built guns are made this way. A stock offset to the left, for shooting from the left shoulder is said to be Cast On.
Chamber - An area at the breech end of a barrel, of about the diameter of the cartridge for which the gun was intended, and into which the cartridge is inserted just prior to being fired. This is a high pressure containment area which is very precisely aligned with the bore of the barrel.
Checkering - A regular pattern of fine grooves cut into the surface of a stock to aid in gripping a gun.
Cheekpiece - A broad, flat, raised area on the side of a buttstock.
Choke - A carefully measured constriction of the bore of a shotgun at the muzzle, designed to control the spread of the shot as it leaves the barrel.
Choke tubes - Short, interchangeable cylinders, of subtly different internal tapers, that screw into a threaded recess at the muzzle of a shotgun. By inserting different choke tubes, one can alter the shot pattern thrown by the gun. Choke tubes should be tightened until snug. Guns fitted for choke tubes should never be fired without tubes inserted.
Claw Extractor - An essential design element of the Mauser 98 bolt action and its derivatives: the Springfield '03 and the Winchester pre-'64 Model 70. A large, long extractor is mounted to and revolves around the bolt shaft---or more properly, remains stationary in the receiver raceway when the bolt revolves. This claw takes positive hold of the cartridge coming from the magazine and places it in the chamber when the bolt is closed. Then, when the bolt is opened, the claw, never having relinquished its grip on the rim of the cartridge, withdraws it from the chamber with absolute reliability.
Claw Mounts - A quick-detachable scope mounting system, popular in Germany and Austria. The front of the scope is fitted with a hook-shaped tentacle which is inserted into a slot in a fixed front scope base. The rear of the scope is fitted with another set of hook-shaped tentacles. When these are pressed sharply downwards into their opposing receptacles they snap into place, held by a spring-loaded clasp, locking the scope into position. When properly installed, claw mounts are generally considered the best quick-detachable system for scope mounting: the cleanest looking, the easiest to operate and the most accurate in returning to zero.
Clicks - A unit of adjustment for a sight. Typically equal to one quarter of one MOA, but may range from one eighth to one half of one MOA.
Clip - A simple, disposable narrow spring-lined channel-rail in which cartridges are supplied for military weapons. The shooter positions the clip vertically above the firearm's magazine, then pressing down with the thumb, slides the cartridges from the clip and down into the magazine.
Centerfire Cartridge - A cartridge that has a primer located in the center of the base of the shell casing. This is as opposed to a rimfire cartridge.
rooster, Half - A notch in the sear and hammer that forestalls accidental hammer fall, which would fire the gun. When on half rooster, the hammer is disengaged from the trigger mechanism, hence the gun is safe while the hammer is in this position. In some revolvers, placing the hammer in the half rooster position allows rotating the cylinder for loading or unloading.
Cocked - A state of readiness of a firearm. The hammer (or similar mechanism if there is no hammer) only needs to be released by the trigger to cause the gun to fire.
Cocker/De-Cocker - A type of action on a break-open gun or rifle where, in place of a traditional top tang safety, a somewhat more robust tab is fitted. Normally such a gun is carried in the field loaded, but with the action not cocked---an exceedingly safe condition. Then, when ready to fire, the shooter, instead of pushing a safety tab forward, pushes this larger tab forward, cocking the mainspring, making the gun ready to fire. Then, if the shot is not taken, he may simply slide this tab rearwards again, de-cocking the gun and returning it to the still-loaded, but very safe position. Or, in German: Handspanner.
Cocking Indicators - Small devices attached to the internal hammers of a break-open gun and visible from the exterior of the gun to show when each barrel is cocked and when it has been fired. These are usually in the form of protruding pins on a boxlock gun or in the form of engraved or gold inlaid lines on the tumbler pins of a sidelock gun.
Coin-finish generally refers to a high-polish finish, bright steel on the receiver of a break-open gun. Other action-body finishes could be case-hardened, blued or French-gray (a chemical-finish, dull gray steel color). Coin-finish, when appearing typically on a modern, high grade Italian shotgun shows off the exquisite and delicate engraving better than other finishes. The term is sometimes used (incorrectly) by people dealing in old guns to describe the finish on a well-worn gunís receiver when all the original case-hardening colors have worn or have been polished off.
Cold clean bore - The first shot from a rifle that has been cleaned, and not fired recently may go to a different point of impact, for the same point of aim than a rifle that has been fired recently. This first shot is referred to as a shot from a cold, clean, bore.
COM - Center Of Mass. For combat or self-defensive shooters, COM represents the area of an assailant's torso within which the most vital organs are likely to be disrupted by a gunshot. Shooting to COM is considered the most expedient way to stop an assailant from continuing threatening behavior.
Comb - The top of a gun's stock, where a shooter rests his cheek when mounting a gun.
Combination Gun - A firearm with various different configurations of rifle and shotgun barrels.
Commemorative - In firearms parlance, a gun that was manufactured in "limited" numbers (often into the thousands), marked, stamped or fitted with extra bells and whistles in such a way as to evoke reverence to some famous person, place or historical event. Rather than to be manufactured for honest use, a commemorative is manufactured specifically to be collected.
Compound - A term used by law enforcement and the media to demonize a firearms owner when referring to his home.
Confiscation - A means of disarmament. To take away.
Cross Pin Fastener - A horizontal wedge, press-fit through the forend of a vintage gun, through a lump attached to the underside of the barrel and out the other side of the forend. To secure the forend in position. Also called a key fastener.
Crown - The finish contour of the muzzle or a rifle. May be flat or rounded. Often shows effective chamfering to protect the critical rifling at the absolute end of the muzzle.
Curios or Relics - is defined in 27 CFR 178.11 as follows: "Firearms which are of special interest to collectors by reason of some quality other than is associated with firearms intended for sporting use or as offensive or defensive weapons. To be recognized as curios or relics, firearms must fall within one of the following categories:
Firearms which were manufactured at least 50 years prior to the current date, but not including replicas thereof;
Firearms which are certified by the curator of a municipal, State, or Federal museum which exhibits firearms to be curios or relics of museum interest; and
Any other firearms which derive a substantial part of their monetary value from the fact that they are novel, rare, bizarre, or because of their association with some historical figure, period, or event. Proof of qualification of a particular firearm under this category may be established by evidence of present value and evidence that like firearms are not available except as collector's items, or that the value of like firearms available in ordinary channels is substantially less."
A list of acknowledged "Curios or Relics" is available from the Bureau of Alcohol, Tobacco and Firearms, Firearms Technology Branch, Room 6450, 650 Massachusetts Avenue NW, Washington, DC 20226 or at: http://www.atf.gov/publications/download/p/atf-p-5300-11/atf-p-5300-11.pdf
A special Curios or Relics license is available from the BATF, which allows collectors to buy eligible firearms in interstate commerce. A licensed collector is not authorized to engage in business as a dealer in any firearms, including curios or relics.
Cylinder - That part of a modern revolver that holds cartridges in separate chambers radially around a central hingepin. The cylinder revolves as the handgun is cocked, bringing each successive cartridge into position, and locked into alignment with the barrel for firing.
More to come...