Compendium of Terminology

A
Accuracy – General term, usually referring to the inherent ability of a rifle to consistently group all its shots close together on a target at a given distance under perfect conditions. It takes no account of human error, wind conditions, etc.
Also applied to a given load, brand of ammo, bullet, etc., or to a combination of rifle and cartridge. See Group.
In sniping, the ability of the sniper and his weapon to deliver precision fire on a desired target. Accuracy can easily be measured as the ability to group all shots close to a desired impact point. The deviation from the desired impact point or the size of the group is a function of range. Accuracy is the product of uniformity.

Action – The combination of the receiver or frame and breech bolt together with the other parts of the mechanism of a sniper rifle or other firearm that normally performs loading, feeding, locking, firing, unlocking, extracting, and ejection.

Adjustable Objective – Fine focusing ring on the objective lens of a telescope that helps to eliminate parallax.

Adjusted Aiming Point – An aiming point that allows for gravity, wind, target movement, zero changes, or MOPP firing.

Aggregate – The sum total of all targets in competitive shooting; final score.

Aluminium Jacketed Hollow Point – ( Bullet ) abbr. AJHP.

Ammunition – One or more loaded cartridges consisting of a primed case, propellant and, with or without, one or more projectiles, depending on the type of weapon used.

Ammunition Lot – A quantity of cartridges made by one manufacturer under uniform conditions from the same materials. Ammunition within a lot is expected to perform in a uniform manner.

Ammunition Lot Number – Code number that identifies a particular quantity of ammunition from one manufacturer. It is usually printed on the ammunition case and the individual boxes in which the ammunition comes.

Annealing – The process of making brass more malleable by controlled heating followed by rapid cooling. Usually applied to the neck and shoulder area of cases which are to be reformed to a calibre or design different from the original ( makes them less prone to cracking during the reforming process ). This should not be done to the head of the case, since reducing the strength of this part may result in failures.

Anvil – Internal part of Boxer primer. The anvil is raised in the centre to form a cone, and has three legs which rest against the bottom of the primer pocket, spanning the flash hole. It offers concentrated resistance to the firing pin as it dents the primer, crushing the priming compound between them, which is ignited by the resulting sharp friction.

Arsenal – A manufacturing or storage facility for arms and ammunition. Best known in the United States for their development work are Frankford Arsenal, Picatinny Arsenal and Watertown Arsenal. A term often applied to the collection of firearms owned by an individual or a group.

Assault Rifle – A military rifle intended purely for one-man operation and equipped to provide both semiautomatic or full-automatic fire by means of a selector switch or other fire-control device. Today’s assault rifles are typified by the Soviet AK 47 and the U. S. M 16. They are chambered for an intermediate cartridge, have barrels under 20 inches, make extensive use of plastics and stampings, use gas operation and locked breeches, have magazine capacities of 20 to 30 rounds, weigh from six to 10 pounds and are quite compact.

Autoloader – See Semi-automatic.

Automatic – A firearm design that feeds cartridges, fires and ejects cartridge cases as long as the trigger is fully depressed and there are cartridges available in the feed system. Actuation of the mechanism may be from an internal power source such as gas pressure or recoil, or external power source, such as electricity. See Semi-automatic.

Automatic Safety – A device on some firearms intended to return the safety to the “On” (safe) position when the action is opened.

B
Backlash – The distance the trigger travels after let-off.

Baffles – Barriers to contain bullets and to reduce, redirect or suppress sound waves. Baffles are placed either overhead, alongside or at ground level.

Ball – In military nomenclature this term refers to the bullet.

Ball Ammunition – General-purpose standard service ammunition with a solid core (usually of lead) bullet.

Ball Powder – A propellant with spherical granules, usually denser than extruded powders, hence better for small cases. Developed by Western Cartridge Company around the start of World War II.

Ballistic Coefficient ( BC ) – A mathematical factor representing the ratio of the sectional density of a bullet to its coefficient of form. Simply put, BC expresses a bullet’s length ( relative to diameter ) and aerodynamic shape, thus indicating its ability to overcome air resistance in flight. The higher its BC factor, the better a bullet retains its velocity and energy, and the flatter its trajectory. Most bullets have BCs between .100 and .700. Higher BCs are required for long-range shooting.

Ballistics – The science that deals with the motion and flight characteristics of projectiles. It can be divided into three phases:

  1. Internal ballistics
  2. Exterior ballistics
  3. Terminal ballistics

The main aspects of ballistics that concern the rifleman are bullet velocity, stability, kinetic energy, trajectory and penetration/wounding effect.

Barrel – That part of a firearm through which a projectile or shot charge travels under the impetus of powder gases, compressed air, or other like means. May be rifled or smooth-bore. See Rifling.

Barrel Band – Metal band that secures the barrel to the fore-end of a full-length rifle stock.

Barrel Erosion / Barrel Wear – The gradual eroding away of the rifling lands immediately ahead of the chamber throat, resulting in accuracy loss. Metal surface is burned away by the intensely concentrated powder flame at this point.

Barrel Liner – Thin steel tube usually permanently inserted into the barrel to either change the calibre, restore the gun, or to make the gun more functional when the barrel is formed from softer material.

Barrel Time – The interval between the time the bullet starts to leave its seat until it reaches the muzzle. This is significant because is it linked to recoil time, which affects the point of impact. See Recoil, Point of impact.

Barrelled Action – A combination of barrel and receiver or frame and breech bolt, together with the other parts of the mechanism by which a firearm is loaded, fired and unloaded.

Battered Cartridge – The cartridge is deformed in such a way that it will not chamber in the rifle.

Battle Rifle – Term still used to represent any full size caliber rifle as opposed to a assault rifle cartridge like the .223 or 7.63x39mm. A Main Battle rifle is one designed to fire a full powered cartridge like the 30-06, 8x57mm, 7x57mm and even the 7.62×51 Nato. These rifles are generally large, heavy, and have excessive recoil. The term differentiates them from assault style rifles designed to fire short, light weight and low recoiling rounds.

Bead Sight – The small cylindrical top portion on some forms of front sights.

Bearing Surface – That portion of the bullet surface which bears on, or touches, the bore.

Beat – The sniper’s operational area where established control measures (boundaries, limits) define his territory.

Beavertail Fore-end – The forward part of a one-piece stock. (Shotgun) a larger, wrap-around forearm as opposed to a “splinter” forearm. Also called forearm.

Bedding – Refers to the fit or fitting of the metal parts of the barrel and receiver with the wood stock.

Bell – To open the mouth of a case slightly in order to seat a bullet more easily. Also used in reference to a rifle barrel which is worn at the muzzle ( belled muzzle ).

Belted Case – A “rimless” cartridge case with a raised integral belt around the case just ahead of the extractor groove to provide a positive headspacing surface while retaining the extractor groove ( which facilitates use in Mauser actions ). This type of construction is generally used on large capacity magnum-type cartridges. See Headspace, Magnum, Rim.

Benchrest Rifle – A rifle designed for optimum accuracy while being shot from the shoulder and supported by a specifically designed table (rest). Shooting event utilizing rifles and ammunition designed to deliver extreme accuracy at long ranges.

Berdan Primer – A primer containing no internal anvil. In the Berdan system, the anvil is an integral part of the cartridge case, formed by a conical projection rising from the floor of the primer pocket, and flanked by ( normally ) twin flash holes. Berdan cases are not convenient for reloading, as depriming requires special equipment and is time-consuming. Some claim this to be more accurate, since the twin flash holes ensure more even ignition of the powder.

Berm – An embankment used for restricting bullets to a given area or as a dividing wall between ranges. Also backstop, baffle.

Bipod – A two-legged support attached to the fore-end of a rifle, used mainly for long range and/or accurate shooting.

Black Powder – The earliest form of propellant, characterized by the huge cloud of white smoke produced. It is reputed to have been made by the Chinese or Hindus. First used for guns in the 13th Century. It is a mechanical mixture of potassium or sodium nitrate, charcoal and sulphur. High in saltpetre, hence extremely corrosive to barrels if residue is not immediately cleaned out. Replaced around the turn of the century by the cleaner and faster-burning “smokeless” propellants. It is still used by antique firearm (or replica ) enthusiasts. A low-pressure propellant: the firearms were not as strongly built as modern ones, hence should not be used with nitro powder/ammo.

Blackout – Condition where the exit pupil of a scope is smaller than the pupil of the shooter, which results in the target image forming on only part of the eye, with a surrounding black ring. This makes it more difficult to focus on the target. See exit pupil.

Bloop Tube – It is a tube, with over-calibre inside dimensions, added to the front of a barrel to extend the sight radius. Normally used in target shooting with short-barrelled weapons.

Blown Primer – Where the primer has fallen completely out of its pocket when the cartridge is extracted after firing.

Blue – The chemical oxidation to colour ferrous metal parts various shades of blue or black.

Boat Tail ( BT ) – Bullet of tapered base or truncated conical base design, which raises the ballistic coefficient factor by reducing the aerodynamic drag, providing greater stability at subsonic velocities. Drag partly comes from the effects of cavitation (turbulence) and the progressive reduction of the diameter toward the rear of the bullet allows the air to fill in the void. Originally designed for extreme range machine guns barrages, boat tails offer some ballistic advantage on the target range at 800-1000m, as most match-type bullets have boattails to help flatten trajectory. They have little practical use at shorter ( LE/hunting ) distances, as few modern cartridges drop below the speed of sound at these shorter distances.

Bolt Action – A firearm in which the breech closure is: in line with the bore at all times; manually reciprocated to load, unload and cock; and is locked in place by breech bolt lugs engaging abutments usually in the receiver. There are two principle types of bolt actions, i.e., the turn bolt and the straight pull type.

Bore – The interior of a barrel forward of the chamber.

Bore Diameter – Internal diameter of a barrel measured from the tops of diametrically opposed lands, i.e. the smallest internal diameter. If the lands are not opposed, the diameter of a circle inscribed to touch the tops of the lands. It is the inside diameter of the barrel before the rifling is cut.

Bore Sighting – A method of aligning a barrel on a target by aiming through the bore. May be part of the sight alignment procedure. When sighting in a scope tools like a collimator can be used.

Bottleneck Case – Cartridge case with a neck diameter smaller than its body diameter, hence creating a shoulder.

Boxer Primer – Primer with a 3-legged internal anvil, permitting use of a single, central flash hole in the case head. Such cases can be conveniently deprimed by means of the decapping pin in standard reloading dies.

Brass – Slang for cartridge cases.

Breaking In a Barrel – Process of initial use of a NEW rifle/barrel, by alternately firing and cleaning, a progressively larger number of shots, until a certain number has been reached. This process must be completed before load development for the rifle is started, and/or before the rifle is sighted in for a specific load. One such process is as follows: – Clean before firing – Clean after every shot (w/o the bore brush) for the first 10-20 rounds – Clean after every 5 shots for the next 20-40 shots. – Clean after every 10 shots for another 20-40 shots. – Shoot 20 shots without cleaning before sighting in for good. I’ve seen a few other methods with different progressions in the number of shots/cleaning. I don’t think it matters exactly.

Breech – The chamber end of the barrel.

Breech Face – The part of the action which contacts the rear of the cartridge; the rear end of the barrel.

Bull Barrel – A firearm built with an extra thick walled barrel that adds weight to the muzzle and reduces recoil. Used primarily for target shooting or varmint hunting.

Bullet – The object which is propelled towards the target. This term is often incorrectly used to describe a loaded round of ammunition (cartridge). The ensuing confusion has led to the use of the superfluous term “bullet heads”. The design of the bullet differs for various applications.

Bullet Drop – Term used to describe the measure of a bullet’s fall after it crosses the line of sight for the second time, i.e., beyond the zero or sighted-in range, due to the effect of gravity.

Bullet Drop Compensator – Any device that is integral to the rifle telescope that is designed to compensate for the bullet’s trajectory.

Bullseye – In target shooting, the aiming point or center of the target.

Burning Rate – Rapidity with which a powder burns, relative to other powders. The burning rate will dictate the type of firearm it can be used in, as well as the application.

Butt – (Handguns) Bottom part of the grip. (Long Guns) Rear of shoulder end of stock, which rests against shooter’s shoulder.

C
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.

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.

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:

  1. It gives the bullet its mass-to-size ratio to improve momentum.
  2. 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.
  3. The tungsten core, where used by the military, is used for armour piercing.

  4. 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.

D
Deburring tool – The deburring tool removes burrs from the inside and outside ( chamfer ) of newly trimmed case mouths.

Deflection – The change in the path of the bullet due to wind or passing through a medium.

Deprime, Decap – The process of removing the spent primer from a cartridge case for reloading. This is most often accomplished by the decapping pin in a die during the resizing operation of reloading.

Detailed Search – A systematic observation of a target area in detail, using overlapping observation in a 180 degree area, 50 meters in depth, starting in and working away from the observer.

Deterrent Coating – Varnish-like coating on powder granules to inhibit combustion, for controlling burning rate, to ensure that the power peak is not reached too early inside the chamber.

Detonation – In rifle terms, a near-instantaneous explosion known to occasionally (but not predictably) occur when reduced loads of slow burning powder are used in large capacity cases, and which has totally destroyed rifles.

Dies

  1. In reloading, tools for resizing, full length of neck only, and depriming cases, and seating bullets.
  2. In manufacturing, it swages bullets or cores, extrudes lead wire or draws jackets.

Double-barrel – Two barrels in a firearm mounted to one frame. Can be vertically or horizontally aligned. See over-under and side-by-side ).

Double Base Powder – Smokeless propellant containing nitro-glycerine in addition to the basic nitro-cellulose ingredient.

Double trigger – A term used for firearms having two barrels and a separate trigger for the discharge of each. The two trigger are normally placed one after the other, with the understanding that the back trigger must be used first, since squeezing the front trigger might set of the back trigger as well, resulting in both shots going off simultaneously.

Drag – The aerodynamic resistance to a bullet’s flight.

Dram equivalent – A term used to indicate the approximate velocity of a shot charge by a comparison.

Draw mark – A straight scratch lengthwise on the case due to some foreign substance in the drawing dies.

Drift – Lateral movement of a bullet away from the line of bore, caused by its rotation on its own axis, and always in the direction of the rifling twist (compensated for by sight adjustment). See Magnus effect. Also used to describe the influence of wind on a bullet’s flight path.

Drop – Drop is the vertical distance from the line of sight to the comb, Monte Carlo or heel of the stock. It is measured from an extension of a straight line drawn from the base of the front sight bead across the top surface of the open rear sight adjacent to the notch. When making a custom stock, the drop is specifically adapted to the shooter’s body and shooting style. The drops for target rifles are usually measured from the centreline of the bore.

Drop Safety – Prevents the firing pin from hitting the primer unless the trigger is pulled.

Dropped primer – See Blown primer.

Dry firing – Aiming and firing the weapon without live ammunition. This is an excellent technique to improve marksmanship skills and does not cause any damage to a center-fire firearm. It is best done with an expended case in the chamber to cushion the firing pin’s fall.

Dud – In small arms jargon, a cartridge that misfired. Also see Hangfire.

Dummy Round – Cartridge containing a bullet but no propellant, and an inert primer. Used for safe demonstration of loading procedure, testing of rifle actions, etc. Usually identifiable by hole drilled through case wall.

Duplex load – The use of two different powders in loading the same cartridge. NOTE This is not something that should be undertaken by the handloader at home – it can only be achieved safely under laboratory conditions.

E
Effective Wind – The average of all of the varying winds encountered.

Ejector – Device which expels cartridges or fired cases from a firearm.

Energy (of motion) – Kinetic energy or force carried by a bullet at that point in its trajectory. In common use and popular shooting literature it is expressed in foot-pounds, one ft/lbs being the amount of force required to lift a one-pound weight one foot above the ground. Formula: Energy ( in ft/lbs ) equals bullet weight ( in grains ) multiplied by the velocity ( in feet per second ) squared, divided by 450240. Often wrongly equated with killing power, energy is not a reliable gauge of this, as it does not take into account penetration or bullet performance.

Erosion – The wearing away of the bore due to friction and/or gas cutting. Normally more pronounced in the throat, and that part of the barrel just beyond.

Exit Pupil – The small circle of light seen coming from the ocular lens of an optical device when held at arm’s length. To get the exit pupil of a telescope, simply divide the size of the objective lens ( in millimeters ) by the power of the scope – for variable powered, take the current setting. E.g., 8×40 scope, divide 40 by 8, and get 5. The size of the exit pupil will help in determining the effectiveness of the optical device in low-light conditions. The larger the exit pupil, the better – up to a limit of course. The human eye is normally dilated to about 5mm in normal light, 2-3mm in bright light, and 7-8mm in low light. So you want your exit pupil to be slightly LARGER than pupil of your eye under the conditions you’re using the scope in, otherwise blackout will occur.

Express – Term adopted by British gun makers during late 1800s to denote cartridges of unusually high velocity (named after ‘express train’). There were black powder express (BPE) and later nitro express (NE) cartridges. The rifles also became known as express rifles. Today the Americans call the classic British leaf sights ‘express sights’.

Exterior Ballistics – The branch of applied mechanics which relates to the motion of a projectile from the muzzle of a firearm to the target, i.e. the performance of the projectile during flight. Also see Ballistics, Internal ballistics and Terminal ballistics.

Extractor – Device for withdrawing the cartridge or fired case from the chamber. It is normally part of the action, and consists of the ejector claw and ejector pin.

Extractor Groove – Circumferential groove in the head of a rimless, semi-rim or rebated rim case to provide purchase for the extractor claw.

Eye Relief – The distance that the eye is positioned behind the ocular lens of the telescopic sight. A two-to three-inch distance is average. The sniper adjusts the eye relief to ensure a full field of view. This distance is also necessary to prevent the telescope from striking the sniper’s face during recoil.

F
Feeding Ramp – Upward sloping, slightly concave metal ramp immediately below and in front of the chamber mouth, to guide the cartridge in its travel from magazine to chamber.

Feet Per Second – Unit of measure for velocity. Also see muzzle energy and velocity. Abbreviated ft/s not FPS.

Fg, FFg, FFFg, FFFFg – Common terminology for granulation sizes of black powder, from Fg (coarsest) to FFFFg (finest). Also 1F, 2F, 3F and 4F.

Field Grade – Usually the standard grade of gun with little or no embellishment.

Firearm – An assembly of a barrel and action from which a projectile is propelled by products of combustion.

Fireform – The enlarging/reshaping of a cartridge case to fit a given chamber by firing it in that chamber. Normally neck sizing is performed on the cases when preparing for reloading, as full-length sizing will nullify the effects of fireforming.

Firelapping – Lapping is a process that, done properly, will make the bore of a barrel dimensionally stable, that is to say not vary in physical size, within a certain tolerance level. It will also change the surface finish of the bore. If done right, removing imperfections in a barrel will increase accuracy, the bullet will be more stabile. Also, copper and lead fouling build up in the imperfections, so a smooth bore will require less cleaning. The lapping technique can also be varied such that the bore diameter tapers down from chamber to muzzle, which some contend promotes accuracy.

Firing Line – A line parallel to the targets from where firearms are discharged.

Fish-tailing – The result of the bullet base collapsing in the target, causing the bullet to bend and deviate from course.

Fixed Sights – Non-adjustable sights.

Flanged – British term for a rimmed cartridge case.

Flash Hole – In metallic cartridges, the hole/s in the floor of the primer pocket through which the flame from the primer passes to ignite the powder charge.

Flyer – A shot considerably outside a normal group on a target, not representative of the rifle’s or load’s potential accuracy.

Flat Nose ( Bullet ) – Abbreviation FN

Follow-through – The continued mental and physical application of marksmanship fundamentals after each round has been fired.

Foot Pounds – (ft/lbs) Unit of measure for energy, being the amount of energy required to raise one pound in weight one foot above the ground against the normal pull of gravity. Used for bullet kinetic energy. See muzzle energy.

Form Factor – A multiplier (also called the coefficient of reduction) which relates the shape of a bullet to the shape of the standard projectile used to prepare a particular ballistic table.

Fouling – Deposits of powder residue and bullet jacket material or lead in the bore, chamber or works of a firearm after discharge. The powder and jacket fouling require different cleaning solvents for complete removal. Excessive fouling influences accuracy, and can also increase pressure levels. See Leading.

Frame – The metal part of the gun that contains the action.

Free-floating Barrel – A barrel that is completely free of contact with the stock. This is critical to accuracy because of barrel harmonics. As the bullet is travelling down the barrel, the barrel is vibrating like a tuning fork. Any contact with the barrel will dampen or modify these vibrations with (usually) a negative impact on shot-group size or point of impact.

Freebore – (aka ‘barrel throat’) The distance a bullet must travel between chamber and bore before its bearing surfaces contact the lands of the rifling, the purpose being to delay resistance, hence prolong pressure built-up. It cannot be too much, however, as that can cause instability in the bullet. This distance will vary from rifle to rifle, as well as according to the preference of the handloader, as some prefer the bullet to touch the lands, while others prefer it to be further away. Care must be taken not to make this distance too great, as this will adversely affect accuracy. It is not advisable to have the bullet touch the lands, either, as that can increase pressure levels significantly.

Full Metal Jacket – ( Bullet ) jacket bullet with ‘solid nose’ i.e., no lead showing at the tip. Also called solids. Abbreviation FMJ.

G
Gas Check – Shallow copper cup attached to the base of appropriate cast bullets to reduce barrel leading and to protect the base of the bullet from the effects of the burning powder gases.

Gas Leak – Black marks around primer showing where gas has escaped.

Gas Operated – An automatic or semiautomatic type firearm in which the propellant gases are used to unlock the breech bolt and then to complete the cycle of extraction and ejection.

Gauge – A term used in the identification of most shotgun bores, but has no relation to the linear measurement of the bore. (410 bore is an exception). Gauge is determined by the number of perfect spheres which may be obtained from one pound of lead. (Example, a 12-gauge gun has a bore diameter the same as one of the 12 perfect spheres which could be made from a pound of lead. If 20 perfect spheres are made from one pound of lead, the diameter of one of these spheres would be the same as the diameter of the 20-gauge gun). The bore diameters of various gauges are as follows: 10 gauge/.775″; 12 gauge/.725″; 16 gauge/.662″; 20 gauge/.615″; 28 gauge/.550″; 410 gauge/.410″. (abbr. Ga)

Gilding/Guilding Metal – Cupro-nickel (copper/nickel alloy) or copper-zinc alloy used for bullet jackets.

Girth – The smallest circumferential dimension at the pistol grip of a stock.

Grain – Measure of weight applied to bullets and powder. 7,000 grains = 1 pound. 1 gram = 15,43 grains.

Greenhill’s Formula – A formula that relates bullet weight and length to rifling twist. Having two of them, the third can be calculated. One must just keep in mind that Greenhill’s formula assumes cylindrical, pure lead bullets, and doesn’t work very as well for small calibres as it does for large bores. L = bullet length in inches D = bullet diameter in inches [150/(L/D)]xD = twist in inches.

Groove – The low point of rifling within a barrel.

Groove Diameter – The diametrical measurement of the bore of a rifled barrel, measured from the bottoms of opposing grooves (i.e. the largest internal dimension). If the grooves are not opposed, the diameter of a circle inscribed to touch the bottoms of the grooves is taken. This measurement should be fractually larger than the true diameter of the appropriate bullet. See Bore diameter.

Group – A cluster of bullet holes made by the same rifle/load combination, formed from numerous shots fired at a target using the same point of aim, for checking accuracy. A 5-shot group of 1½ to 2 inches at 100 yards/meters (measured from the centres of the two widest spaced holes) is generally regarded as acceptable hunting accuracy for factory rifles using factory ammunition. Groups of 1″ at 100 yards are regarded as excellent. For target shooting, especially benchrest, groups under .35″ is the norm. For standardization, it is best to fire five-shot groups with the same aiming point. It is a statistical fact that group size will increase with the number of shots fired.

Group Sizes – It is the maximum distance between the centres of the two farthest shots in a group. The easiest way to do this is to measure from the outside edge of one bullet hole to the inside edge of the farthest one away. Another method is to measure the distance from outside edge to outside edge of the farthest apart holes, then subtract the bullet hole diameter. ( Note that the bullet hole diameter is often smaller than bullet diameter – check it for yourself! ) This latter method allows recording groups smaller than the bullet diameter itself. An example is in some benchrest competitions where the winning group with a 6 PPC rifle ( .243-inch bullet ) will be under 0.2 inches.

H
Hammer – A component part of the firing mechanism which strikes the firing-pin, transfer bar, primer or percussion cap.

Hammerless – A misnomer, it refers to any firearm having a concealed hammer.

Hand Stop – A device attached to the weapon’s fore-end (modified with a metal rail) designed to prevent the supporting hand from sliding forward.

Handload/Reload – Verb: the process (non commercial) of assembling cartridges from their component parts (usually by hobbyists). This gives the handloader the opportunity to assemble ammunition that is far more accurate in his specific rifle than factory ammunition will be, and/or is best suited for his needs. Noun: the product of this process.

Hangfire – Extended delay (up to a second or more) between the firing pin blow and the ignition of the powder, usually caused by old or contaminated primer/propellant which ignites slower than usual. 1. Keep the muzzle pointed in a safe direction. 2. Count to ten SLOWLY. 3. With the opening in the action pointed away from your face, eject the cartridge and examine it. 4. Attempt to determine the cause of the failure. Also see Dud.

Hasty Search – A very rapid check for enemy activity; primarily used as a security measure to determine immediate threats or danger to the sniper when occupying positions.

Head Separation – Separation of the case head from the case body, caused by stretching of the brass, usually due to oversized chamber or excessive headspace. Also caused by cases that has been reloaded many times, with resulting weakening of the brass.

Headspace – The distance from the bolt face (when the bolt is closed) to that surface in the cartridge chamber which stops the case’s forward movement. For bottle-necked cases, the measuring point is centered on the shoulder and is known as the datum line. For belted magnum cases, the headspace is measured from the front of the belt to the head of the case. In practical terms, the amount of free movement a cartridge has in a closed chamber. This dimension is critical for the safety of the shooter, as well as the accuracy of the weapon system. Insufficient headspace hinders complete chambering; excessive headspace permits case stretching, separation or rupture, endangering the shooter.

Heel – The outer edge of the bullet base.

Hide – The term used to describe sniper positions, normally concealed from the enemy.

Hold-off – A shooting technique used to compensate for bullet trajectory by using a modified point of aim above or below the desired point of impact. Also used to describe the modified point of aim used to compensate for wind or target movement. Also known as “Kentucky Windage.”

Hold-over – When aiming at a target beyond the ‘zero’ or ‘sighted-in’ range of a particular rifle/load combination, holding over is the height one must aim above the target (without making mechanical adjustments to the sight) to drop the bullet onto the target. See Bullet Drop.

Hold-under – The modified point of aim used below the target to compensate for a projectile on its upward axis of its trajectory. This is also used when shooting at angles (slopes).

Hollowpoint ( HP ) – Bullet with a cavity in the nose, designed for rapid expansion on impact. The Sierra MatchKing bullets have this design feature to improve accuracy, not for improved terminal effects. This bullet type has been approved by the JAG for combat use. Not generally recommended for hunting. See Controlled Expansion.

Hooded Sight – A front sight that is equipped with a metal canopy. Designed to eliminate light reflections, as well as to protect the sight pillar.

I
Ignition – The process whereby a cartridge is fired: the firing pin strikes the primer, igniting the priming compound, the flame of which passes through the flash hole to ignite the propellant in the cartridge case.

Ignition Time – The interval from the impact on the primer until the pressure rises enough to start the bullet from its seat.

Incipient Rupture – The partial separation of the cartridge case in a circumferential direction above the head.

Indexing Targets – The method that a sniper team employs to identify targets within its effective field of fire.

Inverted Anvil – Anvil in the primer upside down. This condition will cause a misfire.

Inherent Accuracy – The inherent ability of a specific calibre to be more accurate than other calibres in the same class. For example, the .308 is considered to have more potential accuracy than the 30-06, because of its smaller case. The reason is that the powder for a full charge, *completely* fills the .308 case without having to compress it with the bullet. This gives a more consistent powder burn profile than the larger 30-06 case, which has room for the powder to slosh up and down inside the case, causing each shot to be a little different. This is mostly relevant at bench-rest-level situations, where you’re measuring fractions of an inch in group size differences. For hunting purposes, it’s not really significant.

Internal Ballistics – The science/study of ballistics which deals with all the aspects of the combustion phenomena occurring within the gun barrel, including pressure development and motion of the projectile along the bore of the firearm, i.e. all events until the moment the projectile exits the muzzle. Also see Ballistics, External ballistics, Terminal ballistics.

Iron Sights – A term that is broadly used to describe metallic sighting instruments, covering common open sights as well as aperture-type receiver sights (as opposed to scope sights).

J
Jacket – Envelope of a copper- or steel-covered bullet. Its purpose is to prevent breakage or malformation of the bullet caused by the terrific pressure exerted upon it during detonation and the heat generated in overcoming resistance on its flight towards the target. It is open at one end to allow for internal expansion during flight.

Jacketed Hollow Point – ( Bullet ) Abbreviation JHP.

K
Kentucky Windage – An estimate of the modified point of aim required to compensate for wind or for target movement. Synonymous with hold-off.

Keyhole – Elongated hole made in a target by a bullet that is tumbling in flight, hence strikes the target other than point first. Caused by inadequate rotational stabilization of the bullet (usually due to insufficient barrel twist; the twist is “too slow”), deflection of the bullet by objects in the bullet’s path, or other factors.

Killing Power – Vague term applied to a cartridge’s ability to kill an animal quickly with a single shot, assuming adequate bullet placement. Often wrongly equated with bullet energy. Killing power cannot be measured in precise terms, as neither it nor bullet energy take into account factors such as penetration, bullet performance, etc.

Kinetic Energy – See Energy (of motion).

L
Laminated Case – A case which shows spots where the metal has separated in layers due to scaly inclusions.

Lands – In a rifled barrel, the raised spiral ribs left between the grooves in the bore. This is the part of the barrel that actually engraves the bullet, imparts the spin to the bullet, and ultimately stabilizes the bullet.

Lead – The modified point of aim in front of a moving target needed to ensure a hit. This depends on the range to, and the speed of, the target.

Leading – Traces of lead deposited in the bore by cast bullets, particularly if not adequately lubricated. A build-up of such deposits results in poor accuracy. See Fouling.

Leaky Primer – The escape of gas around the primer pocket, indicated by gas leak around the primer cup.

Length Of Pull – The distance from the centre of the trigger to the centre of the buttplate or recoil pad.

Length Of Stock – The greatest dimension of the stock material.

Lever Action – Usually a repeating type of action with a reciprocating breechblock powered by a finger lever.

Light Blow – A weak firing pin blow, insufficient to discharge the primer properly.

Line Of Bore – Imaginary straight line following the axis of the bore. Of theoretical value only, as a bullet begins to drop below the line of bore from the moment it exits the muzzle. Also known as ‘line of departure’. See Line of sight, Trajectory.

Line Of Sight – Straight line from the shooter’s eye, along the sights to the point of aim. The sights on any rifle are mounted in such a way that the line of bore converges with the line of sight between about 10 and 30 meters from the muzzle, hence the bullet ‘rises’ to cross the line of sight at this point. However, gravity acts on the bullet, giving it a curved flight path which falls to cross the line of sight again at a preselected distance (the ‘zero range’). See Line of bore, Trajectory.

Load – Verb (1) to charge a firearm in preparation for shooting; (2) to assemble a cartridge by priming it, filling it with powder and inserting a bullet. See handload/reload. Noun: describes a given combination of bullet weight, bullet type, primer, powder charge and case.

Loading Density – The ratio of the volume of the powder charge to the volume of the case. The higher the better in terms of accuracy.

Loophole – Firing port. A hole cut to conceal the sniper but allow him to engage targets in his sector.

Low Primer – A primer which is inserted too deep into its pocket. This may result in a hangfire or a misfire.

Lock – A general term referring to the total firing mechanism in a firearm.

Lock Time – The period of time between sear release (when the trigger is pulled) and the fall of the firing pin on the primer (determined by lockwork design). No shooter can hold a rifle absolutely steady, and the longer the lock time, the more opportunity there is to disturb the aim during the firing pin’s travel, resulting in accuracy discrepancies.

Long Gun – A term used to describe shotguns and rifles.

Lube Dent – A dent in a cartridge case caused by using too much lubricant when resizing.

Lube Grooves – Circumferential grooves on a cast lead bullet, containing grease to reduce barrel friction and therefore barrel leading. See Leading, Fouling.

Lube Pad – A pad, impregnated with lubricant, on which cases are rolled before resizing.

Lubricant – Case sizing lubricant is used to reduce friction between the case and the die during the resizing operation in reloading – only applicable to full-length sizing.

M
Magazine – The container holding the ammunition in readiness for chambering in a repeating arm. Usually box-like ( either detachable or built into the receiver ) in which the cartridges are stacked vertically or spirally ( rotary magazine ), sometimes a tube in which they lie nose to tail. In all types, the first cartridge rests on or against a platform or magazine follower which progressively compresses a spring within the magazine as the rounds are loaded into it, the outermost one being held in place by the lips at the mouth. In return, the magazine spring forces the cartridges towards the mouth as each outermost one is scooped off and chambered by the bolt or breech block mechanism. Sometimes also used, wrongly, as alternative for Clip.

Magazine follower – The sliding plate or platform in a magazine, which supports the ammunition, riding atop the magazine spring.

Magnum – A term commonly used to describe a rimfire or centerfire cartridge, or shotshell, that is larger, contains more shot or produces higher velocity than standard cartridges or shells of a given calibre, or gauge. Rifles, handguns or shotguns that are designed to fire magnum cartridges or shells may also be described with the term Magnum. (abbr. Mag).

Magnus effect – A moving, rotating bullet in the air, drags some of the air around with it, in its direction of rotation. This increases the speed in that region, and thus the pressure is lower. Consequently, there is a net force on the bullet in the direction of spin, perpendicular to the forward movement of the bullet. This is called the Magnus effect.

Mannlicher – 19th century Austrian designer/manufacturer who gave his name to a rotary magazine bolt action rifle and cartridges ( 6,5mm & 9,5mm Mannlicher ). Firm since taken over by Steyr who market Steyr-Mannlicher rifles. His name has become synonymous with full-length stocks ( fore-end extended to the muzzle ) which characterised his rifles.

Manually operated safety – A mechanism which prevents a firearm from firing. There are different types, of which some are: Cross bolt: a type of firearm safety operated by lateral force on a button usually located in the trigger guard. Grip: an auxiliary locking device in the grip of some handguns which prevents firing until it is depressed. (example: US 1911 pistol). Half cock: a sear engagement which holds the hammer back away from the firing pin. Hammer block: a device intended to separate the hammer from the firing pin except when the trigger is pulled. Lever: a type of firearm safety operated by the movement of a pivoted lever. (example: Luger pistol). Sliding button: a safety mechanism on a firearm that is operated by a sliding motion. Tang: a safety mounted on the upper receiver tang of a firearm. Thumb: a safety on a firearm so located as to be operated conveniently by the thumb of the trigger hand. Wing: a safety found on bolt action rifles, usually mounted at the rear of the bolt assembly, and pivots up and down at right angles to the bore line in the manner of a bird’s wing.

Match / Match grade – Term to describe ammunition or bullets made with special care for superior accuracy, intended for competitive target shooting. Commercial match-grade jacketed rifle bullets are extremely fragile and should never be used for game hunting.

Match rifle – Specifically designed for target shooting.

Mauser – Famous 19th century German firearm designer of bolt action rifles, semi-auto pistols and several cartridges. Most “standard calibre” rifle cartridges ( i.e. .270, .308, .30-06, etc. ) are based on Mauser’s original 7X57 and 8X57 case head dimensions. Mauser founded the firm Waffenfabrik Mauser Oberndorf ( later known as Mauser Werke, Oberndorf ) which became Germany’s major military arsenal until their defeat in WWII, after which the factories were closed. The company later reopened and today makes sporting rifles.

Mauser action – Usually the famous Model 98 bolt action, widely regarded as the best ever designed, certainly the most widely copied. Originally for military use, identical versions were made by European arsenals under German command, such as DWM, FN, BRNO, etc. Mauser M98 military rifles, commonly ( but inaccurately ) known as “Kk98s”, have become commercially available in large numbers, hence the actions are popular for building sporters. Mauser also made a more refined commercial version prior to WWII, now keenly sought by collectors and custom gunsmiths. The term “Mauser action” is sometimes applied to any action with M98 design features, such as cock-on-opening, controlled feeding ( non-rotating claw extractor ) etc.

Mean Radius – The average radius of shot dispersion from the center of a shot group.

Meplat – The truncated flat area on the leading end of certain projectiles.

Mercuric primers – Primers, usually Berdan type, that have priming compounds containing fulminate of mercury. The trouble with Mercury Fulminate primers is that elemental mercury is released on ignition, and amalgamates with the Copper in the brass, causing it to become brittle. This cannot be prevented, neither can the process be reversed. In the Age of Blackpowder, this was not a problem, as the fouling of the BP absorbed the mercury before it could get into the case metal. It became a problem with the higher pressure smokeless loadings. Also see Corrosive primers.

Mid range trajectory – In its curved path, the highest vertical distance reached by a bullet above the line of sight. The term is a misnomer as the highest point in a bullet’s trajectory does not occur at “mid-range” but slightly beyond ( due to the bullet’s progressive slowing, the curve is in the form of a parabola, not a perfect arc ). MRT figures also apply to given loads and also depend on the height of the scope ( or sights ) above the bore. Useful for determining how low one needs to aim when a small target is closer than the zero range of the scope. See Line of sight, Trajectory.

Mil – An angular unit of measurement equal to 1/6400 of a complete revolution (there are 6400 mils in 360 degrees). The mil is used to estimate distance and size based on the mil relation formula: 1 mil equals 1 meter at 1,000 meters. There are 3.375 MOA in 1 mil.

Minute of Angle ( MOA ) – Angular unit of measure used to describe the accuracy potential of rifles, ammunition, bullets or loads. One MOA equals 1/60th of a degree ( 21 600 minutes in a circle ) and subtends 1.047 inches at 100 yards, or, for practical purposes, 1″ at 100 yards. In hunting terms, a rifle/load which, at 100 yards, can consistently place five consecutive shots in a cluster measuring 1″ between the centres of the two outermost holes ( “minute of angle groups” ) is considered extremely accurate. For Benchrest competitions the figure is obviously much less. See Group.

Mirage – The heat waves or the reflection of light through layers of air of different densities and temperatures. With optical aids, mirage can be seen even on the coldest days. Mirage is used to estimate the effective wind to be applied to the sight of the SWS.

Misfire – A failure of the priming mixture to be initiated after the primer has been struck by a firing-pin or the failure of the initiated primer to ignite the powder.

Modern – A legal term applied to cartridge firearms manufactured after 1895.

Momentum – The product of a bullet’s weight in pounds multiplied by its velocity. Commonly expressed as pounds/feet (lbs/ft); i.e., 9mmP 115gr bullet at 1175fps. (115 / 7000) * 1175 = 19.3 lbs/ft.

Monolithic bullets – A bullet that is formed from one single piece of material. It is normally lathe-turned, and made from a copper alloy. Because copper is a lighter material than lead, monolithic bullets of the same weight and calibre are normally longer than their leaded counterparts, which might cause problems in some rifle, both as far as length and barrel twist is concerned. Normally a monolithic bullet will have better weight retention in a target than a lead-core bullet, which can shed its core. For hunting purposes this means that a lighter bullet can be used, with the same effects. Also called monometal bullets. Also see Full-metal jacket, Solid-nose bullet.

Monte Carlo – A stock with a raised comb to bring the eye in alignment with the sight.

Mouth – The opening at the neck end of a cartridge case, via which the bullet is seated.

Mushroom – Verb: The expansion process of a bullet as it penetrates a target, during which the front end enlarges in diameter ( in the shape of a mushroom on its side ). Purpose is to cause maximum tissue destruction for rapid death or incapacitation, by creating a larger wound channel than the calibre of the bullet. Noun: A recovered bullet which has successfully expanded. See Controlled Expansion.

Musket – Military firearm with long barrel and fore-end or forearm extending nearly to muzzle.

Muzzle – The end of a gun barrel from which the bullet or shot emerges.

Muzzle brake – Device at the muzzle end usually integral with the barrel that uses the emerging gas behind a projectile to reduce recoil. See Compensator.

Muzzle energy ( ME ) – Kinetic energy or force carried by a bullet as it exits the muzzle of a firearm. See Energy.

Muzzle Velocity – The speed of a projectile as it leaves the muzzle of the weapon. ( Industry standard for measuring is 15″ from muzzle.)

N
Natural Point of Aim – The direction that the body/rifle combination is oriented while in a stable, relaxed firing position.

Natural Respiratory Pause – The temporary cessation of breathing after an exhalation and before an inhalation.

Neck, Case Neck – The section of a cartridge case which holds the bullet, which is inserted via the case mouth.

Neck Down, Neck Up – To re-form the neck of a case to accept bullets of smaller or larger diameter respectively. Done to create new calibres ( Wildcats ) or to make cases for calibres ( for which brass is unavailable due to the calibre being ) that are obsolete or very scarce. See Cartridge conversion.

Neck Ream – To reduce the thickness of the walls of a case neck by shaving brass from either the interior or the exterior surfaces. Done to provide even tension on the bullet for optimum accuracy, or when case forming causes forward “brass flow” which makes the neck walls too thick.

Neck Reamer – Cutting tool used for neck reaming.

Neck (re)Sizing – In handloading, to resize the case neck only ( or a part thereof ) without sizing the case body. Done for enhanced accuracy and extended case life, using a special die. It is used in conjunction with fireforming.

Nitro-cellulose – Highly flammable substance made by treating cellulose with nitric acid. Used for making smokeless or “nitro” propellants.

Nitro Express – Term adopted in the late 19th century to describe rifle cartridges charged with nitro-cellulose or “smokeless ( as distinct from “black” ) powder, giving increased or “express train” velocities.

Nitro Proofing – The process of testing a firearm for strength with specific reference to nitro-cellulose ( smokeless ) powder which generates much higher pressures than black powder. Many cartridges were converted from black powder to smokeless without undergoing dimensional changes, thus both types can be fired in the same firearm. If an arm was made and proofed for black powder loads only, it is normally not safe for use with smokeless powder cartridges. Before firing modern ammunition in an old ( pre-1900 ) firearm, check to see that the firearm bears the appropriate symbols to show it has been nitro proofed. See Proofing and Proof marks.

Non-corrosive Primers – Primers containing no substance which is corrosive to barrels. Modern primers are non-corrosive. See Corrosive primers.

O
Objective Lens – The lens at the front of the telescope, facing the target. It is usually larger in diameter than the ocular lens.

Obturation – The sealing of propellant gases within the chamber of the firearm.

Ocular Lens – The lens at the rear of the telescope, nearest the sniper’s eye.

Off-hand position / Off-hand shot – A shooting position in which the shooter stands upright and does not rest the rifle or his arms on or against any object.

Off-hand rifle – A target rifle designed to be held, not rested.

Ogive – The curved or tapering section of a bullet’s sides, forward of the bearing surface ( i.e. between the cylindrical section and the nose tip. )

Open sight – Rear sight of traditional “leaf” type with open-topped V-notch or U-notch, as distinct from a scope or aperture ( peep ) sight.

Over bore capacity – Common term to describe cartridges with powder capacity overly large in relation to the bore. Expanding ( burning ) gas can only be forced through a given aperture at a certain rate; thereafter, increasing the amount of gas ( by increasing the amount of powder ) merely raises pressures without raising velocity ( a .300 H&H case necked down to .22 calibre has twice the powder capacity of a .22-250, but produces maximum velocities that are no higher. ) Cartridges which are over bore capacity include some Weatherby calibres, the .264 Win Mag, and even the .25-06.

Over-and-under ( O/U ) – Firearms with two barrels placed one above the other, as distinct from a side-by-side.

Overall Length ( OAL ) – The total length of a cartridge, measured from bullet tip to base of case.

Overtravel – Continued rearward movement of the trigger after the sear has been released. The better triggers are adjustable for minimum overtravel, to minimize disturbance of the aim while the bullet is still in the barrel.

P
Palm Rest – An adjustable support for a target rifle extending downward from the forearm.

Parallax – The apparent movement of the target in relation to the reticle when the sniper moves his eye in relation to the ocular lens. When the target’s image is not focused on the same focal plane as the telescope’s reticle, parallax is the result. Current issue U.S. Army rifle telescopes have a field parallax adjustment that makes parallax error an insignificant factor when proper eye relief and stock weld are used.

Patch – 1. A piece of cloth used with a rod to clean the bore of a firearm. 2. A piece of paper wrapped around a lead bullet to prevent leading of the barrel and to improve the gas seal. 3. In muzzle loading firearms, the piece of cloth surrounding the bullet or ball to improve the gas seal.

Partial Resizing – In handloading, the resizing of the case neck, without pushing the shoulder back. Slight resizing of a section of the walls near the case head also occurs. Done by raising the full length resizing die a couple of turns in the press. Achieves virtually the same benefits as neck sizing, without the need for a special die. See Neck sizing.

Peep Sight – Rear sight in the form of an aperture mounted close to the shooter’s eye. Shooter “peeps” through the aperture, centring the front sight in the circle of the rear sight picture. The longer sight radius facilitates higher practical accuracy potential, and the system reduces the number of objects on which the eye must focus from three ( rear sight, front sight and target ) to two. Also known as aperture sight, receiver sight or ghost ring.

Piece – General term used for any firearm, e.g. “carrying a piece”. Originated from the term “fowling piece” which was a muzzle-loading shotgun.

Pierced Primer – Cartridge primer that has been pierced by the firing pin. Dangerous because the flame from the primer ( and even from the main powder charge jetting back though the flash hole ) can rush along the bolt tunnel to exit around the cocking piece, endangering the shooter’s eyes. Causes can be firing pin that is set to strike too deep, or too soft a primer.

Pitting – Term to describe small pits in the surface of gun metal ( usually in the bore ) caused by rust or corrosion from mercuric primers. Also see Barrel erosion / Barrel wear.

Plinking – The informal shooting at inanimate objects located at arbitrary or indefinite distances from the firing point.

Plinking Load – A handload which, for reasons of economy and reduced recoil, wear and tear, etc., is milder than the standard, and uses cheaper components, e.g. cast bullets. Normally used more to “keep in shape”, than to do serious shooting.

Point Blank – A term especially related to hunting. The distance to which one can shoot at an animal, hitting in the target area, for example the vital ( heart/lung ) area, without any holdover. The mid-range trajectory and the bullet drop will both fall within the specified area.

Point Of Aim – The point on a target on which the sights are optically aligned when firing.

Point Of Impact – The point on which the bullet actually lands. By adjusting the sights, the point of impact can be made to coincide with the point of aim at a preselected distance; hence we say the rifle/sight/load combination is “zeroed” or “sighted in” at that range. Abbreviated POI.

Pointed Soft Point – (Bullet) abbr. PSP.

Port

  1. An opening in the wall of a barrel to allow gas to operate a mechanism or reduce sensible recoil.
  2. An opening in a receiver to allow loading or ejection.

Powder / Gun Powder – The propellant, either smokeless ( nitro ) or black powder, used in cartridges or muzzle loaders, which burns to produce the expanding gases that force the bullet down the bore, propelling it to the target.

Powder Charge – See Charge.

Powder Funnel – A helpful accessory in handloading that facilitates the transfer of the powder from a scale pan or measure to a cartridge case.

Powder Measure – An adjustable volumetric measure that metres out uniform charges of powder. Used in the handloading of cartridges.

Powder Residue / Powder Ash – The deposit left in the bore, chamber and action of firearms after firing. If not cleaned out, will build up and cause inaccuracy in rifles and mechanical failure in semi-auto weapons and revolvers.

Powder Scale – A device used to weigh charges of powder. Normally of the balance beam type where markers, called “poise”, are moved along a weight-graduated beam to the desired weight point. The scale pan is then filled until the balance point is reached.

Press – Mechanical device used in conjunction with dies for handloading ammunition.

Pressure – See Chamber pressure.

Primer – Small explosive metal cup in the head of a cartridge, containing fast-burning priming compound which, when ignited by friction ( by a blow from the firing pin ) provides the primary flash ( actually, a shock wave ) which ignites the main charge, thus converting the propellant powder into a gas. ( See Anvil, Berdan primer, Boxer primer, Flash hole and Ignition. )

Primer Blow-back – Primer in which gas pressure has blown out the section opposite the firing pin hole. May be due to weak main spring or to a firing pin that is too light.

Primer Indent – The dent or imprint made on the face of the primer by the firing pin. If cratered or pierced, it can indicate excessive pressures ( results of an overload ), or mechanical problems with the rifle.

Primer Leak – An escape of gas around the sides of the primer, usually the result of an overload. Evidenced by a dark circular smudge around the circumference of the primer in the case head. In severe cases the primer pocket will stretch so that the loosened primer falls out as the bolt is opened ( known as a “blown primer” ).

Primer Pocket – The recess in the base of the cartridge case that accepts the primer. In military ammunition, it is usually crimped and sealed with a lacquer sealant for water-proofing.

Primer Set-back – After firing primer is partly out of its seat.

Probability of Hit – Refers to the chance (denoted as a percentage) that a given round will hit the target at a given range. PoH values range from 0 to 100.

Progressive Powder – Slow-burning propellant that produces a more gradual pressure build-up.

Projectile – A bullet in flight. Often wrongly used to mean a bullet per se. A bullet does not become a projectile until it is in flight.

Proofing – The process of testing a firearm for strength by firing a cartridge in it that generates higher pressures than normal. If the firearm passes the test, it is deemed safe for use with normal loads. See Nitro proofing and Proof marks.

Proof Marks – Official symbols stamped onto the barrel of a firearm that has been proofed, to show that it is safe to use with standard ammunition appropriate to that firearm. Symbols differ from country to country. See Nitro proofing and Proofing.

Propellant – Another word for gun powder. See Powder.

Pump – A firearm action featuring a movable forearm which is manually actuated in motion parallel to the barrel. Forearm motion is transmitted to a breech bolt assembly which performs all the functions of the firing cycle assigned to it by the design. This type action is very prevalent in rimfire rifles and shotguns and to a lesser extent in centerfire rifles. Also called slide or trombone action. Usually associated with a tubular magazine.

Punctured primer – See Pierced primer.

R
Rail – A metal track installed in the fore-end of weapon to accept a hand stop or sling.

Ram – The main shaft of a metallic cartridge reloading press.

Ramp / Sight Ramp – The steel base on which some sights are mounted.

Range – The distance between the shooter and the target. Also short for shooting range.

Rangefinder – Device for determining range, or for optically measuring ( or estimating ) the direct distance to a target.

Ranging – The technique that a sniper uses to compensate for bullet trajectory by adjusting the ballistic cam of an adjustable/ranging telescope.

Rate Of Twist – In a barrel, the length over which the rifling grooves make one complete twist ( i.e. the length of the bore used to turn the bullet one full revolution ) e.g. 1:10 or one revolution in 10 inches. Differs from calibre to calibre. Bullet weight must be appropriate to the rate of twist or bullets will not stabilise in flight. The heavier the bullet, thus the longer, the faster the twist rate must be. See Greenhill’s formula.

Rebated Rim – See Rim

Receiver – The basic unit of a firearm which houses the firing and breech mechanism and to which the barrel and stock are assembled, i.e. the rigid metal housing which contains the working parts of the action ( bolt, striker, trigger mechanism, etc. ). Called the “breech body” in England. In revolvers, pistols and break-open shotguns, it is called the frame.

Receiver Sight – See Peep sight.

Rechamber – To alter the chamber of a barrel to take a cartridge other than the original, e.g. reaming out a .308 Win chamber to .30-06 dimensions. Can only be done for cartridges having the same bullet diameter, e.g. 7X57 to 7X64.

Recoil – The rearward thrust of a firearm caused by the propulsion of a projectile in the opposite direction. Refer Newton’s 3rd Law of Physics: for every action there is an equal but opposite reaction. Commonly called “kick”. The amount of recoil felt by the shooter depends on factors such as the weight of the rifle ( which absorbs some of the recoil ), the design of the stock, the shooting position, etc. Incidentally complete analysis based on conservation of momentum would have to include the angular momentum the bullet acquires, which depends on the twist rate and length of the barrel…

Recoil Lug – The heavy metal protrusion beneath the front of the action designed to stabilize the action in the stock and transfer the recoil to the stock.

Recoil Operated – An automatic or semiautomatic type firearm in which the force of recoil is used to unlock the breech bolt and then to complete the cycle of extracting, ejecting and reloading, as opposed to Gas operated.

Recoil Pad – A rubber or leather pad at the end of the butt to absorb recoil. Can also be some kind of pad on the shoulder of the shooter to absorb the recoil.

Regulate / Barrel Regulation – In double-barrel rifles, the process of getting both barrels to shoot to the same point of impact with a given load at a given distance. This is normally done to around 70 metres. The further away from this regulated distance one shoots, the more one must compensate for left/right point of impact.

Reload – See Handload.

Remaining Energy – A projectile’s energy in foot pounds at a given range.

Repeater – A firearm capable of being fired several times without loading extra ammunition into the firearm. Usually applied to rifles and carbines. Any firearm equipped with a magazine.

Retina – The light-sensitive layer at the back of the eye. It consists of rod (black/white sensitive for night vision) and cone (colour sensitive for day vision) cells.

Resize – In reloading ammunition, the forcing of the fired case into a sizer die to reduce to its original ( unfired ) dimensions ( it swells in the chamber when fired ). See also Neck (re)sizing.

Resizing Die – The reloading die that resizes fired cartridge cases and removes spent primers by means of a decapping pin. See dies.

Reticle / Reticule

  1. In telescopic sights, the element which is optically referred to the target. It may consist of straight or tapered cross-hairs (wires in the tube forming a central cross ), dots, or other marks used to determine the point-of-aim, size of, or range to the target.
  2. Markings in a microscope eyepiece used to establish location or scale. Commonly used to measure rifling.

Rifle Cant – Any leaning of the rifle to the left or right from a vertical position during firing. This should be eliminated because of the potential for increasing misses at longer ranges.

Rifling – Spiral grooves in the bore of a barrel to impart a rotary motion ( spin ) to the bullet to provide it with rotational stability. This will ensure that the bullet flies true with a point-first attitude.. Methods of manufacturing are Button rifling, Cut rifling and Hammer forging. See Lands, Rate of Twist.

Rim – On a cartridge case, the lip or flange around the case head, which provides purchase for the extractor claw. Initially all cases had projecting rims, i.e. rims larger in diameter than the case body, e.g. .303 ( today these are known as “rimmed” or “flanged” cases ). The Mauser bolt action with its ( then ) unique extractor system gave us the “rimless” case, e.g. 7X57, .30-06, which is not really rimless, but has a non-projecting rim of the same diameter as the case body. The rim is formed by a groove cut around the periphery of the case head. “Rebated rims” are smaller in diameter than the case body ( .425 Westley Richards ), as well as “semi-rimmed” cases ( only slightly larger in diameter than the case body, but also with an extractor groove ) e.g. .220 Swift.

Rimfire – A flange-headed cartridge ( e.g. .22LR ) which has its priming compound in the hollow rim of the case ( the rim is in the form of a fold in the drawn brass, which is very thin ). The firing pin can strike anywhere on the rim. Opposed to Centre-fire cartridges, these cannot be reloaded.

Rings – ( Not Scope rings. ) Circular marks around the case, due to poor reaming of the chamber.

Rolling Block – Single shot action in which a breech block and hammer each rotate about their separate transverse pins in the receiver. The two members are swung rearward, away from the barrel breech to load the mechanism or extract a cartridge case. To fire a cartridge, the breech block is closed and locking is accomplished by the falling hammer engaging an abutment on the breech block.

Rotary Magazine – See Magazine

Round – Another word for Cartridge.

Round Nose – (Bullet) Abbreviation RN. A bullet design which features a rounded nose.

Ruptured Case – Cartridge case that splits or bursts open on firing, due to problems such as excessive headspace, oversized chamber, fatigued or brittle brass, etc. Extremely dangerous, as the escaping gases can blind or otherwise injure the shooter.

Running Game Target – An Olympic Shooting event whereby competitors shoot 22 calibre rifles at life-sized lithographs of a boar with a target superimposed on it. The target moves on a track at various speeds and the shooter must track each target and fire before it disappears. (abbr. RGT).

S
SAAMI – Abbreviation for Sporting Arms and Ammunition Manufacturers’ Institute.

Safety Shooting Glasses – Eye protection and sight improvement specifically designed for, and which should always be used, when shooting firearms.

Scope – A shortened form of the word “telescope”, meaning a telescopic sighting device for a firearm or, simply “riflescope”. While a telescope magnifies an image, a riflescope is made with an integral fire-direction indicator called a reticle which, most often, appears as crossed-hairs or crossed-wires. A riflescope is securely mounted on a firearm and adjusted so that its vertical cross-wire is aligned with the path of the fired projectile. The horizontal cross wire is then set to coincide with the projectile’s point of impact at a specific distance. It magnifies the target and places it and the reticle in the same optical place, facilitating very precise aiming.

Scope Mounts – Devices for securing a scope to a rifle, comprising scope rings and bases.

Scout – An individual who is usually ahead of his parent organization to conduct surveillance on the enemy, conduct reconnaissance, and report information to his parent organization.

Sear – That part of a trigger mechanism ( usually a notch or shoulder on the trigger arm ) which holds the striker ( hammer or firing pin ) in the cocked position until the trigger is pulled. Cocking the striker against its spring automatically engages the sear. Pulling the trigger disengages the sear, releasing the striker onto the primer.

Season Crack – A cracking which occurs in hard brass with the passage of time. Usually seen in cartridges as Split necks.

Seating Depth – The depth to which a bullet is seated below the case mouth.

Seating Die – The reloading die that presses the bullet into the neck of the cartridge case, crimping the case if so desired.

Sectional Density ( SD ) – A mathematical factor expressing the ratio of a bullet’s mass ( weight ) to its cross sectional area. SD relates a bullet’s diameter to its length ( in a given calibre, the heavier a bullet is, the longer it is ). All other factors being equal, bullets that are longer in relation to their diameter retain their velocity better, hence have flatter trajectories, hit with higher energy, and penetrate deeper, than bullets that are shorted relative to their diameter. SD does not take into account the aerodynamic shape of a bullet, which also influences velocity retention, trajectory, etc. Useful only for comparing bullets of similar shape, or when incorporating into Ballistic Coefficient factors.

Semi-automatic / Semi-auto – Term to describe a firearm of firearm action that is self-loading. The action is cycled ( or “cocked” ) by hand to feed the first round into the chamber, thereafter it cycles, ( i.e. fires, extracts, ejects and reloads ) automatically each time the trigger is pulled, until the magazine is empty. Can be gas-operated or recoil-operated. Semi-autos will fire one shot only – pressure on the trigger must be relaxed and reapplied for each shot. Such weapons are often wrongly called automatics.

Semi-rimmed Case – See Rim

Service Rifle – The primary rifle of a military force.

Set Trigger – Trigger mechanism with two different weights of pull, one normal or heavy, and one very light ( aka a “hair trigger” ). There are two types: a single set trigger, the “hair” setting of which is engaged by pressing the trigger forward prior to firing ( otherwise it works as a standard trigger ); and a double set trigger, which comprises two separate triggers, the rear of which does not fire the piece, but is pulled to set the front one on “hair” ( failing which the front one will work as a standard trigger ).

Shank – The parallel-sided or cylindrical section of a bullet.

Shellholder – In a reloading press, the bracket fitted to the top of a ram, which grips the case rim to secure the case for sizing, decapping, bullet seating, etc.

Shells – In smallarms terms, slang for cartridges, especially shotgun cartridges ( USA: “shotshells” ). Rarely used to mean cartridge cases, except as in shellholder.

Shock – The transference of the kinetic energy of a bullet to animal tissue or other mediums.

Shoulder – The sharply tapering section of a bottleneck cartridge case which separates the neck from the case walls.
Or, in bullet terms, the point at which the head of a projectile joins the cylindrical rear portion, or shank.

Side-by-side – In double-barrelled weapons, barrels horizontally aligned, one beside the other, as distinct from an over-under.

Side-plate – A removable plate in the frame or receiver to allow access to internal parts or upon which some internal parts are mounted.

Sight-in – In rifle shooting, the process of getting the bullet’s point of impact to coincide with the rifle’s point of aim ( or line of sight ) at a preselected distance, by means of sight adjustment. Applies to any given combination of rifle, load and sight system. See Line of Sight, Trajectory, Zero.

Sight Picture – The visual image observed by the shooter when the firearm sights are properly aligned on the point-of-aim.

Sight Radius – The distance between the front and rear elements of mechanical or “iron” sights. Theoretically, the longer the sight radius, the lower the potential for human optical error, hence the more accurate the system. This is true of open sights on longer barrelled rifles, which can have a long sight radius while still keeping the rear sight the proper distance from the shooter’s eye. If the rear sight is too close to the eye, it creates focus problems, potentially affecting aim ( unless it is an aperture or peep sight, which obviates the need for focusing ). For this reason bloop tubes are sometimes used on short-barrelled rifle to extend the sight radius.

Silencer – See suppressor .

Silhouette – A shooting sport characterised by metallic knockdown targets of various shapes and sizes, at various distances, invented in Mexico. Variations include rifle and handgun in centerfire, smallbore and air gun calibres.

Single Action – An action requiring the manual cocking of the hammer before sufficient pressure on the trigger releases the firing mechanism. (abbr. SA), as opposed to double action.

Single Base Powder – Smokeless propellant made from nitro-cellulose base. See Double base powder, Nitro-cellulose.

Single Shot Action – A firearm with no means in the mechanism for storing or loading more than the cartridge housed in the chamber of the barrel.

Single Stage Trigger – Trigger with no free movement prior to releasing the sear; as distinct from double stage ( aka double pull or military type ) which requires some additional “slack” to be taken up before it releases the sear.

Sizing – See Resizing

Six o’clock Hold – A sight picture in which the top of the front sight post or bead is held on the bottom edge of the bull’s-eye, as in the 6 o’clock position on a clock face. Firearm must be sighted in to shoot slightly high of point of aim at that distance, so that bullets land in the centre of bull’s-eye. Purpose is to enable the shooter to see the full circle of the bull’s-eye for more precise reference, rather than to partially obscure it with the foresight.

Slide – A member attached to and reciprocating with the breech block.

Slug – Verb ( as in “slug” the barrel ): the process of determining the precise groove diameter of a barrel by driving a slightly oversized soft lead lug through the bore and measuring its broadest diameter.
Noun: slang for bullet.

Smokeless Powder – Propellant based on nitro-cellulose, or nitro-cellulose and nitro-glycerine. Smokeless powder gives off no smoke and is non-corrosive, as distinct from black powder which creates voluminous clouds of white smoke and leaves corrosive deposits in the bore. Smokeless powder largely replaced black powder during the 1880s and 1890s; it facilitates higher velocities but generates higher pressures. See Nitro Proofing.

Sniper Specialist – An individual trained in sniper employment (preferably sniper qualified) who advises the commander or operations officer (S3) on proper sniper employment.

Sniper Team – Two snipers of equal training and ability; the foundation of sound sniper employment.

Soft Nose Bullet / Soft Point Bullet – A bullet design providing for exposure of a portion of the core at the nose or tip of a jacketed bullet to initiate expansion for the bullet to “mushroom” in the target.

Soft Head – Spreading of the head and opening of the primer pocket on firing, due to over-annealing of the head of the cartridge.

Solid Nose bullet / Solid – Traditionally, a jacketed bullet with “blind” nose, i.e. no lead exposed at the tip ( non-expanding ) designed for maximum penetration on large game. Also called Full Metal Jacket ( FMJ ) bullets. Term now also applies to bullets that are lathe-turned from copper, brass, etc., known as monolithic.

Speed of Sound – 1120.22 fps at standard conditions. Projectiles travelling faster than this pass through the sound barrier twice. Once as it exceeds the sound barrier (within the barrel) and once when it re-enters subsonic speeds. This effect causes a sonic crack that can be used to pinpoint the firer.

Spire Point – ( Bullet ) Pointed conical bullet. Same as Soft Point, also abbreviated SP.

Spitzer – A bullet design having a sharp pointed, long ogive.

Split Body – A longitudal crack in the body of the case near the head. This is a dangerous defect, as it allows gas to escape to the rear.

Split Neck – A crack in the neck of the case. It is usually due to failure to anneal the neck sufficiently to prevent Season cracking.

Stabilize – In rifles, to put the right amount of spin on a bullet ( by means of the spiral grooves in the bore ) to enable it to maintain an equilibrium in flight. A bullet that rotates on its own long axis at the correct rate will fly true; one which does not spin at all, or spins too slowly or too rapidly for its length, will wobble or tumble, causing it to be inaccurate and fall short. See Keyhole, Rate of Twist.

Stalking – The sniper’s art of moving unseen into a firing position, engaging his target, and then withdrawing undetected.

Stock Dimensions -General stock dimensions consist of the following: cast, drop at comb/Monte Carlo/heel, girth, length of pull, length of stock, pitch.

Stock Weld – The contact of the cheek with the stock of the weapon.

Stovepipe – Malfunction occurring when a case gets stuck between the breech face and the slide.

Straight Pull – Type of bolt action operated by pulling straight back on the handle, instead of first rotating the bolt by hand ( the bolt self-rotates on a camming system ). Well-known examples are Ross ( Canadian ), the Schmidt-Rubin ( Swiss ) and the modern Blaser ( German ).

Stretch – A visible strain extending around the case above the head. Usually due to excessive headspace.

Striker – In rifles, a spring-propelled firing pin, or internal hammer which strikes the back of the firing pin.

Suppressor – A device designed to muffle or eliminate the sounds of the discharging of a firearm. It is usually fitted onto the muzzle but can also be an integral assembly with the barrel. This usually works best with subsonic ammunition to eliminate the bullet’s sonic crack as well.

Surveillance – The systematic observation of areas, places, persons, or things by visual, aural electronic, photographic, or other means. The sniper makes extensive use of fixed and roving surveillance to acquire targets or assess target vulnerabilities.

Swage – To pressure-form by forcing through or into a die. Normally used in reference to cast bullets.

Swivel – The attachment point for the sling to the stock.

T
Target Indicators – Any sign that can enable an observer to detect the location of the enemy, his installations, or his equipment.

Telescopic Sight – See Scope.

Terminal Ballistics – That branch of ballistics which deals with the effects of projectiles at the target, i.e. the effect of the projectile on the target. Also see Ballistics, Internal ballistics, External ballistics.

Terminal Velocity – The speed of the bullet upon impact with the target. This will determine the effectiveness of the bullet because of its direct contribution to energy/energy transfer.

Throat – Short, tapered section of barrel’s bore between the chamber and the start of the rifling. See Freebore.

Time Of Flight / Flight Time – The time taken by a bullet to travel from muzzle to target.

Top Break – A firearm action that is hinged at the bottom and “breaks” open at the top for loading. In rifles, applies to single shot and double or multi-barrelled pieces only.

Torque – The turning force applied to screws or bolts.

Trace – The air turbulence created by the shock wave of a bullet as it passes through the air. This air turbulence can be observed (with an optical aid) in the form of a vapour trail as the bullet travels toward the target.

Tracer – Type of ammunition that is visible at night due to its phosphorous compound in the base of the bullet.

Tracking – Engaging moving targets where the lead is established and maintained; moving with the target as the trigger is squeezed.
Also used to describe the technique of following the enemy by his markings left on the terrain.

Trajectory – The path of a bullet in flight. As gravity works on a bullet from the moment it exits from the muzzle, the bullet is constantly falling below the line of bore., hence its trajectory is always curved. Rifle sights are mounted so that when the line of sight is horizontal, the bore is pointing slightly upwards – the bullet’s path rises to cross the line of sight a few metres ( 10 – 30 ) from the muzzle. However, gravity ensures that it falls to cross the line of sight a second time, much further away. By adjusting the sights, this second crossing can be made to occur at the distance of your choice, hence we say the rifle/scope/load combination is “sighted in” or “zeroed” at that distance. See Line of bore, Line of sight, Mid-range trajectory, Sight-in, Zero.

Trapping – A technique for engaging moving targets. The aiming point is established forward of the target. The rifle is held stationary and fired as the target approaches the aiming point.

Trigger Pull – The force ( usually in lbs ) that must be applied to a trigger for it to release the sear. Term also refers to the quality of the release. A good trigger pull will be appropriately light, and the release will be a clean, sharp snap, with no gritty “creep”.

Trim-to Length – In handloading, the length a cartridge case should be trimmed back to after it has stretched past its “maximum case length”.

Turnbolt – Another name for bolt action.

Turret Press – A handloadingpress with a rotatable multi-station turret top for positioning dies and powder measure in their appropriate sequence.

Turrets – The two round, capped projections on the top and side of a scope tube which house the adjustment dials.

Twist – See Rate of twist.

V
Velocity – The speed of a bullet, usually measured in feet per second.

Vernier Calliper – A slide-type graduated instrument used to measure overall cartridge and case lengths precisely.

W
Wad Cutter – A bullet design which features a sharp shoulder. Designed to cut a clean, round hole in a paper target.

Web – That portion of a cartridge case between the bottom of the primer pocket and the interior of the case.

Wildcat – A non-commercial cartridge; a cartridge designed and made by a handloader, by altering an existing case. See Cartridge conversion, Neck down/up.

Windage – The adjustment on the telescope or iron sights to compensate for horizontal deflection of the bullet.
The distance or amount of horizontal correction that a sniper must use to hit his target due to the effects of wind or drift.

Work-harden – Brass becomes harder as it is worked. See anneal.

X
X – The power of optical magnification (for example, 10X, 3X-9X).

X-Ring – Center of a target. The bulls-eye.

Y
Yaw – The action of a projectile spinning erratically around its own axis.
Z
Zero – The range at which the point of aim and the point of impact are one and the same.
Verb: To sight in a rifle/scope/load combination so that the bullet’s point of impact coincides with the point of aim at a preselected distance. Called this because at that distance, zero hold-over is required when aiming. See Bullet drop, Hold-over, Line of sight, Trajectory.