Glossary
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A
ACP:
Abbreviation for Automatic Colt Pistol. Normally used to designate
a cartridge, as in the 45 ACP.
Ammunition:
An assembled group of components, bullet, primer, cartridge case
and powder, necessary for loading and discharging a firearm. Frequently
abbreviated as “ammo”.
Anneal:
A heat treating process which can be used to restore the ductility
to brass that has been work hardened. In the case of brass, annealing
always softens the metal.
Antimony:
A metal, frequently used to harden lead by alloying the
two. Other metals, such as tin, may be added to the alloy as well.
Anvil:
A point against which priming compound can be crushed by the blow
of the firing pin, causing detonation. Anvils may be a separate
piece pressed into the primer itself (Boxer type), or an integral
part of the case, as in the Berdan system.
Automatic
Weapon: Any firearm which discharges multiple shots with
a single actuation of the trigger. In common usage, the term is
often applied erroneously to describe what should be described as
an autoloading, semi-automatic or self-loading firearm.
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B
Backed-Out
Primer: A primer which, upon firing, has been pushed slightly
out from the primer pocket. Primers backing out generally indicates
an excessive headspace situation, usually in conjunction with a
light load. Can be caused by light loads alone, in some circumstances.
Also referred to as a popped or protruded primer.
Ballistics:
The science of projectiles in motion. When applied to firearms,
it is normally divided into interior ballistics, exterior ballistics,
and terminal ballistics.
Ballistic
Coefficient: A mathematical expression of a bullets ability
to overcome atmospheric resistance (drag), as compared to a specified
“standard” reference projectile. Generally abbreviated
as BC.
Balloon
Head: A drawn cartridge case in which the primer actually
extends into the powder chamber. This results in a rather weak web
area, making the cases suitable for light loads only. Although long
discontinued, they may still be encountered in old cartridges such
as the .45 Colt, .44-40 WCF, or .45-70 Government. Balloon head
cases are best relegated to the case collector, and should not be
reloaded.
Ball:
Military nomenclature for a single round of small-arms ammunition.
Refers specifically to lead or steel-cored jacketed ammunition,
as opposed to more specialized tracer or armor-piercing ammunition.
Ball
Powder: Any of a series of double-base powders developed
by Olin, having a spherical or flattened spherical shape. Examples
would include Winchester’s 231, 748, or 760 powders.
Barrel/Cylinder
Gap: The distance from the face of a revolver’s cylinder
to the face of the barrel. Normally, this is somewhere in the range
of .003" TO .006", depending on the manufacturers specifications.
Battery:
As applied to firearms, the position of readiness for firing. A
firearm is referred to as being “in-battery” when the
locking mechanism is fully closed and the action is ready to be
fired.
Bearing
Surface: The area of a bullet which actually contacts the
lands and grooves during its passage through the barrel.
Belted
Case: A case having a raised band, or belt, around the
base just ahead of the extractor grove. Intended to provide positive
headspacing on cartridges with long, sloping shoulders, the belt
allows the cartridge to feed and function more reliably than a rimmed
case. Contrary to the common misconception, the belt adds nothing
to the strength of the case.
Berdan
Case/Primer: A primer/case system, designed by Col. Hiram
Berdan, having two or more flash holes, and an anvil formed into
the primer pocket. Although widely used throughout the world, this
system has never been popular in the U.S., due largely to the difficulty
in reloading Berdan cases.
Black
Powder: An explosive propellant composed of potassium nitrate,
charcoal, and sulfur.
Blitz:
Sierra’s line of thin-jacketed bullets, designed to expand
or fragment violently upon impact. Especially favored for varmint
hunting where ricochets may be a problem.
BlitzKing:
Any of Sierra’s family of high-performance varmint bullets
utilizing an acetal resin tip. Combining high ballistic coefficient
and outstanding accuracy with explosive terminal performance, they
offer varminters the ultimate in field effectiveness.
Boat
Tail: A tapered section between a bullets bearing surface
and base, intended to reduce the effects of drag. This, in turn,
gives the bullet a higher ballistic coefficient than a comparable
flat-based bullet.
Bolt:
That portion of a firearms action which contains the extractor and
firing pin/striker mechanisms. It may or may not also serve to lock
the mechanism.
Bolt
Thrust: The force exerted on the bolt face by gas pressure
upon ignition, normally expressed in units of pounds per square
inch (psi).
Bore:
The inside portion of a barrel. In a rifled barrel, the bore diameter
refers to the measurement from the top of one land, to the top of
the opposing land; the inside diameter of the barrel before the
rifling is cut.
Bore
Capacity: A term used to describe the volume of the bore
as it relates to its ability to effectively burn a given amount
or type of powder, with a certain combination of components. A cartridge
which may be “over bore capacity” with one type of powder,
may be perfectly suited to another powder of a different burning
rate. Specifically, bore capacity for a given component combination
is indicated by the point (or DELTA) at which the pressure and velocity
curves begin to separate.
Bore
Guide: An aid used during the cleaning process to help
keep the cleaning rod centered in the bore, reducing the chance
of damage to the throat. May replace the bolt, in the case of bolt
action rifles, or may fit over the muzzle, as with the M14. Sometimes
called a “cleaning bolt.”
Bore
Sight: To bring the sights into rough alignment with the
bore visually, or with a collimator. Bore sighting is done in preparation
to firing for zero; it is never a replacement for actual firing.
Boxer
Case/Primer: A primer/case system, designed by Col. Edward
Boxer, having one flash hole located in the center of the primer
pocket and a separate anvil pressed into the primer cup. Due to
its ease of reloading, the Boxer system is best suited to the handloaders
needs. Ironically, the system invented by an Englishman (Boxer)
is most prevalent in the U.S., while an American system (Berdan’s)
is used in England and Europe.
Brass:
An alloy of copper and zinc. Brass is the most commonly used material
from which metallic cartridge cases are made. The term is also frequently
used to describe the cartridge cases themselves.
Bridging:
A “logjam” type accumulation of powder in the mouth area
of a powder measure, which sometimes occurs when using extruded
tubular powders. This causes one charge to be light, and the next
charge thrown to be excessive when the bridged powder falls free;
a potentially hazardous situation.
Brisance:
The shattering or crushing effect of an explosive.
Bullet:
The projectile fired from a firearm. A complete, loaded cartridge
is not a bullet; although a bullet is part of a loaded cartridge.
Bullet
Path: The vertical distance, normally expressed in inches,
above or below a firearms line of sight. The path followed by a
bullet in its flight to a target.
Bullet
Pull: The amount of pull, normally measured in pounds,
needed to pull a bullet from the case mouth. Also referred to as
“neck tension”.
Bullet
Puller: A tool used to extract a bullet from a case or
loaded cartridge or loaded ammunition, or to break down ammunition
which would be unsafe to fire.
Burning
Rate: A term used to describe the relative quickness of
a given powder as compared to a known standard. Burning rate is
extremely important in determining a powders suitability for a given
cartridge.
Bushing
Die: A sizing die, either neck or full length, in which
the neck tension is controlled by using any of a series of interchangeable
bushings to control the outside diameter of the resized case neck.
These bushings are available in increments of .001" to provide virtually
infinite control over the resizing process.
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C
Caliber:
The diameter of a projectile, normally expressed in thousandths
of an inch when discussing small arms, although it may also be expressed
in metric units. May also refer to bore or groove diameter, again,
either in inches or millimeters.
Caliper:
A measuring instrument consisting of adjustable jaws used to determine
thickness, diameter or length. An essential tool for the handloader.
Cannelure:
A cut or pressed groove (or grooves) around the shank of a bullet.
Cannelures provide an area into which the case mouth may be securely
crimped. Also known as “crimping grooves.”
Cap:
A percussion cap. The percussion cap was a early form of primer,
composed of a small metal cup charged with a priming mixture (such
as fulminate of mercury). Percussion caps are still used in most
black powder firearms. Although not technically correct, the term
is still used in reference to primers.
Cartridge:
A single, complete round of ammunition. See “ammunition”.
The first cartridges consisted of the components (powder and bullet)
which were contained in a casing of paper. The term “cartridge”
comes from the Latin word for paper, “charta”, a direct
reference to these early beginnings. Modern cartridges normally
consist of 1) a case, 2) a bullet(s), 3) a primer, and 4) the powder
charge.
Case:
The portion of a cartridge which holds or contains all other components.
Also known as a “shell”, “brass”, “cartridge
case” or “hull”.
Case
Forming: Forming a case, such as a .30-06, into another,
such as a .25-06. This may be accomplished by the use of dies alone,
or it may involve fire forming. Also referred to as “reforming.”
Case
Trimmer: A tool for cutting cases back to length after
being stretched by firing or reforming.
Cast
Bullet: A bullet produced by pouring molten lead (or lead
alloy) into a mould.
Center
Fire: Ammunition which has a primer located in the center
of its base. Most center fire cartridges are reloadable.
Chamber:
That area of a firearm into which the cartridge is loaded in preparation
for firing, and which supports the cartridge during firing.
Chamber
Cast: A casting of a firearms chamber(s), normally done
with Woods metal, Cerrosafe, or a similar low melting-point alloy.
Making a chamber cast is sometimes necessary to check chamber or
throat dimensions.
Chamfer:
To remove burrs on the inside of a case mouth by cutting
a slight bevel or taper. Chamfering reduces the possibility of damage
to the bullet base, or the case itself, during the seating process.
Charge:
The specified amount of a particular powder loaded into a case.
The act of putting powder into a case.
Chronograph:
An instrument used in determining the velocity of a projectile.
Most are based on the time taken by a projectile to traverse a known
distance between two points. Chronographs, while long used by the
military and commercial ammunition manufacturers, have only become
commonly available to the handloader within the last 20-30 years.
Clip:
A device which holds ammunition to be charged into a magazine. Clips
may be inserted into the firearm and remain there during firing,
as with the M1 Garand, or may be used only to aid in charging the
magazine, as with the 1903 Springfield, M14, or M16s. This latter
type is referred to as a “stripper clip”, while the former
is called a “charger clip.”
CMP:
The Civilian Marksmanship Program. The CMP was originally created
by the U.S. Congress. The CMP evolved out of the older (and no longer
operational) Director of Civilian Marksmanship. The original purpose
was to provide civilians an opportunity to learn and practice marksmanship
skills so they would be skilled marksmen (or marksmanship instructors)
if later called on to serve the U.S. military. The CMP operates
through a network of affiliated clubs and associations that cover
every state in the U.S.
Collimator:
In reference to firearms, a collimator is an optical device
used to “bore sight” a rifle or handgun. In use, a pilot,
or spud, is inserted into the muzzle and the sights are aligned
by means of a screen attached to the spud. While this may be done
as the first step in “zeroing” a gun, it is never a replacement
for range firing.
Compressed
Charge: A load in which the seating of the bullet actually
causes some compression of the powder. This situation is quite normal
when using some of the slower-burning powders commonly used in the
large-capacity Magnums.
Cordite:
An early extruded, smokeless, double-base propellant widely used
in England. Cordite is distinguished by its length, which normally
ran the full length of the powder chamber. Invented in 1889, cordite
served as the basis for many of our currently used extruded propellants.
Corrosive
Primer: Any primer using potassium chlorate in its priming
compound. When fired, a portion of this will become potassium chloride,
similar to common table salt, and be deposited in the barrel, causing
corrosion (rusting) very rapidly. Cleaning, using normal powder
and copper solvents will not remove the corrosion causing residue
left in the bore. These deposits can easily be removed by using
warm water, followed by standard cleaning and oiling.
Crimp:
A turning inward of a case mouth to increase its tension
on a bullet. Crimping is necessary when loading for revolvers, tubular
magazines, and some rifles with extremely heavy recoil.
Crimped
Primer: Refers to a primer which has been staked, stabbed
or otherwise crimped into the primer pocket. Commonly found on military
cases, the remnants of this crimp must be removed by swaging or
reaming before another primer is seated.
Crown:
The point of the bore where the rifling terminates at the muzzle.
CUP:
Abbreviation for “Copper Units of Pressure”.
This relates to the pressure measured in a copper crusher testing
system. There is no direct correlation between CUP and pressure
expressed in pounds per square inch (PSI), and no conversion factor
to extrapolate one from the other.
Cupronickel:
An alloy of copper and nickel, also known as “German Silver.”
Cupronickel was once used extensively as a jacket material, despite
a serious tendency to leave metal fouling in the barrel. In the
U.S., it has been replaced almost entirely by gilding metal.
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D
DCM:
Director of Civilian Marksmanship
Deburr:
To remove any burrs around the inside or outside of a case mouth.
Burrs are a normal byproduct of case trimming, and must be removed
before reloading the case.
Decap:
To remove a spent primer from a case.
Deterrent
Coating: A chemical coating applied to powders, in order
to bring their burning rates and characteristics into line with
the manufacturers specifications for that particular powder type.
Dies:
In reloading, the tooling by which the resizing, reforming, case
neck expanding, bullet seating, or bullet swaging operations are
performed. Normally used in conjunction with a reloading press.
Double-Base:
A powder which uses both nitrocellulose and nitroglycerine as an
explosive base, as opposed to a single-base powder, which uses only
nitrocellu-lose. Double-base powders generally have a higher energy
content, and as such, can be somewhat more erosive than comparable
single-base powders.
Drop:
The vertical distance between the bullet and its line of departure,
normally measured in inches at a given range. Drop is caused by
the effects of gravity upon a projectile.
Drop
Tube: A powder funnel having a short length of tubing (usually
5" to 6") to settle the powder kernels more compactly within the
case. The result is an increase in the amount of propellant which
can be charged into the case.
Dum-Dum:
A term applied to some early expanding bullets for the .303 service
cartridge loaded by the British arsenal at Dum-Dum, India, prior
to 1899. Frequently used (incorrectly) by the media and others unfamiliar
with firearms to indicate any expanding bullet.
Duplex
Load: A load utilizing two different type of powder; usually
a faster powder near the primer, and a slower one for the main charge.
Duplex loading is intended to give higher velocities, smoother pressure
curves, and greater powder efficiency.
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E
Energy:
The capacity for performing work. In ballistics, kinetic energy
is normally expressed in units of “foot-pounds.” One foot-pound
is equivalent to the energy required to lift one pound one foot
against the force of gravity.
Engraving:
The impressed indentations left on a bullets bearing surface, during
its passage through the bore.
Erosion:
The wear, usually in the throat area of a barrel, caused by extreme
heat and friction. Erosion occurs in all firearms but is aggravated
by rapid fire, large case capacity, or the use of hotter burning
powders.
Expander
Ball: A ball or plug, used to expand a case mouth to accept
a bullet. In dies for bottlenecked cases, the expander is usually
found on the decapping stem. An expander ball should be approximately
.001" to .002" under bullet diameter to assure proper neck tension.
Expansion
Ratio: A mathematical expression for the relationship of
the volume of the bore and powder chamber, to that of the powder
chamber alone. Expansion
ratio is a critical factor in predicting the performance capabilities
of a gun/cartridge combination.
Exterior
Ballistics: The branch of ballistics which deals with the
projectiles flight, from the time it leaves the muzzle, until it
impacts on target.
Extruded
Tubular Powder: A type of smokeless powder formed by forcing
it through a die, and cutting it to specified length. Extruded tubular
powders are more or less cylindrical in shape, and may have one
or more perforations running through its length. Common examples
of extruded powders are IMR 4350, H4895, or Accurate 3100.
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F
Far
Zero: The second point at which the bullet path crosses
the line of sight. This is the commonly referred to “zero”
for a given firearm, at which the point of aim and point of impact
coincide.
Fireform:
To alter the shape of a case by firing it, generally done to increase
case capacity. Upon firing, pressure forces the case out to fit
the chamber, creating the new dimensions desired. Fireforming is
a common technique in making wildcat or improved cases.
Firing
Pin: That portion of a firearm which strikes the primer,
causing ignition.
Flash
Hole: A hole, or holes, from the primer pocket to the powder
chamber of a cartridge case.
Flat
Nose: A bullet design having a broad, flat, meplat. In
most tubular magazines, the point of one round rests on the primer
of the cartridge in front of it, creating a potentially hazardous
situation. Flat nose bullets are intended for use in these magazines
to reduce the possibility of recoil causing detonation in the remaining
rounds.
FMJ:
Common abbreviation for “Full Metal Jacket”, indicating
a bullet having no exposed lead on the frontal portion. FMJ’s
are non-expanding bullets, used in both rifles and pistols. They
are produced in several different configurations, i.e., round nose,
spitzer, spitzer boat tail, etc., depending on their intended use.
Forcing
Cone: The section of a revolver or shotgun barrel just
ahead of the chamber(s) which gradually reduces in diameter to bore
or land diameter. The forcing cone serves to align the bullet or
shot charge with the bore, while preventing deformation to the projectile(s).
FPJ:
Full Profile Jacket. Sierra’s designation for a line of pistol
or revolver bullets which have the jacket extending to the nose
of the bullet. FPJs are intended to hold together well on silhouettes
and other targets requiring deep penetration and minimal expansion.
FPS:
Abbreviation for “Feet Per Second”, usually in reference
to the speed of a given projectile(s).
Freebore:
Essentially, the throat area of a barrel. Normally, use of the term
“free-bore” indicates the rifle in question has an unusually
long throat, as is the case in most of the Weatherby chamberings.
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G
GameKing:
Sierra’s line of boat tailed hunting bullets. GameKings may
be either hollow-point or spitzer in configuration, but all are
of boat tail design.
Gas:
The rapidly expanding vapor caused by combustion. As the gas expands
in an enclosed chamber (the cartridge case), it generates tremendous
pressure. It is this pressure which drives the projectile to the
target.
Gas
Check: A protective cup of copper, brass, or gilding metal
placed on the base of a cast bullet. Gas checks are intended to
reduce deformation of the bullets base due to pressure or hot gases.
Gas
Operated: In firearms, a gun system which utilizes a portion
of the gases produced by the powders combustion to cycle the action.
The military M1, M14, and M16 are all examples of gas operated weapons.
Gilding
Metal: An alloy of 90 to 95% copper, 5 to 10% zinc, now
used extensively as a jacket material.
Grain:
A unit of weight equaling 1/7,000th of a pound. The most common
unit of weight measurement for the handloader; bullets are measured
in grains, as are charge weights of powder. There are 7,000 grains
in a pound, 437.5 grains in one ounce.
Greenhill
Formula: A mathematical formula developed by Sir Alfred
Greenhill to determine the twist necessary to stabilize an elongated
bullet. The Greenhill formula states, the twist required (in calibers)
equals 150 divided by the length of the bullet (in calibers).
Grooves:
The area between the lands in the bore of a rifled firearm. The
grooves are cut or impressed into the surface of the bore, and serve
to impart spin to the projectile.
Group:
The pattern formed by a series of shots on a target, fired generally
using the same aiming point, from the same range. Group size is
used to determine a firearms accuracy potential. While there are
several ways of measuring group size, the most common for the average
shooter is the extreme spread of the two widest shots.
Gun
Powder: The propellant powder used in cap and ball, muzzle-
loading, and black powder cartridge firearms. Although frequently
applied to any small arms propellant, the term “gun powder”
denotes black powder specifically.
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H
Hangfire:
A delay, sometimes quite noticeable, between the strike of the firing
pin and the actual ignition of the cartridge.
Head:
As applied to cartridges, the base area of the case. This area encompasses
the primer pocket, extractor groove, and the rim or belt, extending
up to the body of the case.
Head
Separation: A circumferential cracking around the body
of the case, usually just above the web area. A complete head separation
will normally leave the forward portion of the case in the chamber
upon extraction. Generally caused by excessive headspace.
Headspace:
The amount of play between the case head and the breech face, in
a fully closed action. Insufficient headspace will cause difficulty
in chambering, while excessive headspace will result in head separations.
Headspace problems may be the fault of either the gun, the ammunition,
or a combination of both.
Head
Stamp: A series of letters, numbers, or characters stamped
into the head of a cartridge case to denote caliber, type, manufacturer,
date of production or other pertinent information.
Heel:
The slight radiused portion of a bullet between the base and the
main body.
High
Primer: A primer which has not been fully seated in the
primer pocket, and extends slightly above the head of the case.
High primers can be a dangerous defect, and can result in slam fires.
This is especially true in any form of autoloading firearm.
Hollow
Point: A type of bullet having an opening in the nose.
Hollow points may be of either the hunting, or target styles. Contrary
to popular opinion, hollow points are not always designed to expand
on impact. Match grade hollow point target bullets, for example,
rarely exhibit any expansion when used on game.
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I
Ignition
Time: The time interval between the impact of the striker
or firing pin on the primer, and a rise in pressure sufficient to
start the bullet from its seat.
IHMSA:
International Handgun Metallic Silhouette Association
Improved:
A cartridge having increased capacity over another “parent”
case. Usually achieved by increasing the shoulder angle, decreasing
the body taper, or both. This is most frequently accomplished by
fireforming.
IMR:
Improved Military Rifle. A series of single-base extruded tubular
powders developed by Du Pont. Currently being manufactured by the
IMR powder company.
Ingalls’Tables:
A set of ballistics tables computed by Col. James Ingalls, in which
the drag characteristics of a “standard” projectile are
used as a reference for comparison of other small arms bullets.
The ballistic coefficients of almost all U.S. manufactured bullets
can be referenced to Ingalls’ tables, with only a slight degree
of error.
Interior
Ballistics: The branch of ballistics dealing with events
occurring between the detonation of the primer and the projectile
leaving the muzzle.
Instrumental
Velocity: The velocity of a projectile as registered on
a chronograph. Instrumental velocity is the average velocity of
the projectile as it traverses the distance between the “start”
and “stop” screens of the unit; in short, the velocity
midway between them. If an actual muzzle velocity is needed, the
instrumental velocity must be corrected to the muzzle. With modern
chronographs, given their short screen spacings and a “start”
screen only a few feet in front of the muzzle, this is generally
unnecessary, and the corrections rarely amount to more than a few
feet per second.
IPSC:
International Practical Shooters Confederation
IWBA:
International Wound Ballistics Association
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J
Jacket:
An outer sheath, covering the interior portion (core) of a bullet.
Many different materials, including steel, have been used in making
jackets, but today, 95/5 gilding metal is the standard for the industry.
JHC:
Jacketed Hollow Cavity. A line of expanding handgun bullets designed
by Sierra. JHCs are distinguished by having an internal cavity larger
than the opening at the meplat.
JHP:
Jacketed Hollow Point. Any of Sierra’s line of hollow point
pistol bullets, primarily intended for use in autoloading handguns.
Jacketed hollow points are designed to provide reliable feeding,
while maintaining excellent expansion characteristics.
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K
Kernel:
A single, individual piece of powder. Sometimes also referred to
as a grain of powder, but must not be confused with the unit of
weight. See “Grain”.
Key
Hole: A elongated hole on target, indicating that the bullet
was not traveling point-on at impact. Keyholing may be a slightly
“out-of-round” hole, or it may be a complete bullet-shaped
hole, where the projectile actually went through the target sideways.
This normally indicates a stability problem.
Kinetic
Energy: See “Energy.”
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L
Land(s):
The raised portions of bore extending above the grooves
in a rifled barrel.
Leade:
The minute portion of a barrels rifling which slopes from the unrifled
throat to the full-depth rifling. Although frequently referred to
as the throat, there is a definite difference between the two.
Leading:
A build-up or accumulation of lead in the barrel of a firearm,
caused by using cast or swaged bullets. This can be controlled to
a considerable degree by using harder alloys, better lubricants,
or lower velocities. Leading causes no permanent harm to a firearm,
but is detrimental to accuracy and can be difficult to remove.
Line
of Departure: A straight line projecting through the axis
of the bore to infinity. While this is the initial direction of
a bullet’s velocity, it should be clearly understood that the
bullet falls away from this line immediately upon leaving the muzzle.
This is primarily due to gravity and other outside forces acting
on the projectile.
Line
of Sight: A straight line passing through the sights of
a firearm to the target.
Load
Density: The weight of the powder charge in grains, divided
by the volume (frequently expressed in grains of water) of the case.
Locking
Lug(s): The protruding lug(s) which engage the receiver
to lock the action closed during firing. Locking lugs are normally
situated on a firearms bolt, although there are exceptions.
Lock
Time: The time interval between the sear’s release
of the striker or firing pin, and the subsequent impact on the primer.
Lubricant:
Any substance used to reduce friction. Specific types are used for
firearm mechanisms, cast bullets, or case resizing.
LUP:
Abbreviation for “Lead Units of Pressure”. This
relates to the pressure measured in a lead crusher testing system.
Most often used in low-pressure applications such as shotguns. There
is no direct correlation between LUPs and pressure expressed in
pounds per square inch (PSI), and no conversion factor to extrapolate
one from the other.
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M
Machine
Gun: An automatic weapon firing a full-size (rifle caliber
or larger) cartridge, usually fired off a bipod, tripod or other
fixed mount. They may be clip, magazine or belt-fed, depending on
the design and intended use. They are most often employed as a crew-served
weapon.
Magazine:
An ammunition reservoir from which cartridges are fed into a firearms
chamber. Magazines may be integral, as in the 1903 Springfield,
or may be detachable, as in M14 and M16 series of weapons. Although
the terms are frequently used interchangeably, a clip and a magazine
are not the same thing.
Magnum:
A designation sometimes attached to a cartridge of greater capacity
or power than others of similar caliber. This can be misleading,
as magnum cartridges are not always the most powerful in their respective
bore sizes. In rifles, the term usually refers to one of the belted
cartridges, based on the original Holland & Holland magnums.
Today, belts are used more for sales appeal than any true ballistic
function.
MatchKing:
The trade name given to any of Sierra’s match-grade target
bullets. All currently produced MatchKings are of hollow-point design,
with all but one (.224" diameter 53 grain MatchKing) having boat
tails. Despite their hollow-point design, MatchKings are not intended
to expand on impact, and should not be used for big-game hunting.
Meplat:
The diameter of the flattened tip at the nose of a bullet.
Mercuric
Primer: Any primer which uses fulminate of mercury as a
component in its priming compound. Cases fired with mercuric primers
should not be reloaded, as the mercury seriously weakens the brass
when fired. Mercuric primers may be either corrosive or non-corrosive,
depending on whether or not they contain potassium chlorate. While
no longer in use, surplus military and old commercial ammunition
may still be encountered which is loaded with these primers.
Metal
Fouling: Metallic residue left in a barrel after firing.
Although the current use of gilding metal has reduced fouling problems,
the shooter still needs to keep a close eye on the condition of
the barrel. This fouling, normally seen as a copper wash in the
bore will have a detrimental effect on accuracy.
Minute
Of Angle: A unit of angular measurement equaling 1/60th
of a degree. One minute of angle works out very close to one inch
per hundred yards, making it a convenient measurement for shooters
to use in describing accuracy, sight elevation or windage deflection.
Also referred to as “MOA,” or “minutes.” One
minute of angle = 1.0472" @ 100 yards.
Misfire:
The complete failure of a cartridge to fire after being struck by
the firing pin or striker.
Momentum:
Expressed in units of “pound-seconds,” momentum is a quantity
of motion. Momentum is obtained by multiplying a bullets mass times
its velocity. In many instances, momentum may be a better indicator
of a bullet’s potential than kinetic energy.
Muzzle:
The end portion of a firearms barrel; the point from which the bullet
exits.
Muzzle
Energy: The kinetic energy generated by a projectile as
it leaves the muzzle.
Muzzle
Pressure: The gas pressure remaining as the bullet exits
the muzzle. High muzzle pressures tend to produce greater muzzle
blast.
Muzzle
Velocity: The initial velocity of a projectile as it exits
the muzzle.
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N
NBRSA:
National Bench Rest Shooters Association
Neck:
The parallel-sided portion of a case that grips the bullet. In a
bottlenecked case, it is the area immediately ahead of the shoulder.
Neck
Up or Down: To change the size of a case neck, to reload
with a bullet of larger or smaller diameter than the parent cartridge.
As an example, the .30-06 case could be necked up to form a .35
Whelen, or necked down to form a .25-06. This is normally accomplished
either by a sizing die, or by fireforming.
Neck
Size: To resize only the neck area of a cartridge case.
Neck sizing is accomplished without the die touching the shoulder
or body of a case.
Neck
Turning: An operation performed on the neck of a case to
improve concentricity. This is accomplished by cutting the outside
surface of the necks to a uniform thickness, while the case is centered
on a mandrel.
NM:
National Match. A reference or marking commonly used on firearm
parts or ammunition to denote a more stringent level of manufacture
or quality control. Most frequently associated with Service Rifles
used in High Power competition, and Service Pistols used for the
Conventional Bullseye National Match Course.
Non-Corrosive
Primer: A primer which contains no potassium chlorate or
similar compounds in its primer mixture. Also refer to: Corrosive
Primer, and Mercuric Primer.
Non-Mercuric
Primer: A primer which contains no fulminate of mercury,
or other mercuric compound in its priming mixture. A mercuric primer
may or may not be corrosive, depending on whether or not it contains
potassium chlorate. Also refer to: Mercuric Primer, and Corrosive
Primer.
NRA:
National Rifle Association
NRMA:
National Reloading Manufacturers Association
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O
OAL:
Over All Length: The total length of a loaded cartridge. May also
be listed as LOA (Length Over All), or COL (Cartridge Overall Length).
Obturation:
The sealing of a bore and chamber by pressure. During the firing
process, pressure swells the case within the chamber, preventing
gas from leaking back into the action. The same pressure, applied
to the base of the projectile causes it to swell or upset, filling
and sealing the bore.
Ogive:
Literally, a French word meaning “pointed arch.” In bullet
design, the ogive is the radiused portion between the bearing surface
and the meplat. This radius is often measured in “calibers.”
OKH:
A series of cartridges designed by Charlie O’Neil, Elmer Keith,
and Don Hopkins.
Out
of Battery Firing: A discharge that takes place when the
firearms locking mechanism is not fully closed. Unlike a slam-fire,
an out of battery firing is normally the result of the shooter intentionally
pulling the trigger. Upon firing, the unsupported case may rupture
and vent gasses back into the action. This is a very hazardous situation
for the shooter, and can destroy the rifle.
Overbore:
A loose term used to describe a case that has more capacity than
it can effectively use with normally available powders. Also see:
Bore Capacity, and Expansion Ratio.
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P
Pierced
Primers: A primer which, upon firing, has been pierced
by the firing pin. This allows gas to flow back into the action,
and can damage the bolt face. A potentially dangerous situation
normally indicating excessively high pressures.
Plinking:
Informal shooting, not following any organized rules of competition.
Plinking is shooting “just for fun,” but all the rules
of safe gun-handling still apply.
Point
Blank Range: The range to which a shooter can obtain a
hit in the vital zone of a target, without holding over or under.
Point blank range is influenced by many variables, including target
size, initial velocity, and ballistic coefficient. This term is
frequently misused to refer to extremely close ranges. In reality,
a target may be within point blank range even when it is several
hundred yards away, depending on the variables mentioned.
Port
Pressure: Applies only to gas operated firearms. The amount
of pressure remaining in the bore as the bullet passes the gas port.
If port pressures are too high, damage can result from the violent
cycling of the action. It is important to understand that this can
occur, even when chamber pressures are within acceptable limits.
Port pressure can be controlled by proper powder selection.
Powder
Measure: A reloading tool which dispenses a specific volume
of powder. Most are set for a certain charge through the use of
bushings, or an adjustable powder chamber. Several of the better
units have micrometer adjustable thimbles, allowing the handloader
to return quickly to pre-recorded settings.
Powder
Scale: A scale used to measure powder charges, bullets,
cases, etc. A good scale, accurate to within 1/10th of a grain,
is an important tool for the hand-loader. Most reloading scales
have traditionally been of the balance-beam type, although electronic
units are now becoming quite popular.
Powder
Trickler: A reloading tool used to dribble powder, a kernel
at a time, into the pan of a powder scale. Normally used when the
handloader desires all charges to be absolutely uniform in weight.
Power
Jacket: A Sierra design feature, incorporated into both
rifle and handgun bullets. A series of “skives” are cut
into the mouth of a jacket, to promote uniform and positive expansion.
Pro-Hunter:
Any of Sierra’s flat-base hunting bullets. Depending on their
intended use and caliber, Pro-Hunters are available in a wide range
of weights and nose configurations.
Progressive:
A type of reloading press which advances a number of cases through
the various stages of the reloading operation with every cycling.
Once all stations are full, progressive presses turn out a loaded
round with each stroke of the handle.
Proof
Cartridge: A special high-pressure load used to test the
strength of a newly manufactured or rebuilt firearm. Also referred
to as a “blue pill” load, pressures in these rounds may
run as much as 40% higher than standard for a given cartridge.
Protruding
Primer: Refer to: Backed Out Primer.
PSI:
Pounds per Square Inch.
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Q
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R
Reforming:
To alter the dimensions of a case, either by the use of dies, or
fire-forming. Case reforming is frequently done to make obsolete
or hard to get cases, from another which is readily available. A
mandatory operation when dealing with wildcats and “improved”
cartridges.
Remaining
Energy: The kinetic energy, normally expressed in foot-
pounds, retained by a projectile at a given range.
Remaining
Velocity: The velocity of a projectile, at a given distance
downrange.
Resizing:
Returning a fired case to dimensions which will allow its
being rechambered in a firearm. Normally accomplished via a resizing
die, this may refer to full-length, neck, small-base, or partial
resizing.
Rifling:
The series of spiral grooves, cut or pressed into the bore of a
firearm, intended to impart spin to a projectile.
Rimfire:
Any cartridge having its priming mixture contained within its rim.
For all practical purposes, rimfires are non-reloadable.
Round:
Military terminology for a single, loaded cartridge.
Round
Nose: A type of bullet having a blunt, rounded profile.
Best suited to short range use, due to its poor ballistic shape.
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S
Sabot:
Literally, a French word meaning “shoe.” In weapons systems,
sabots are a device used to center a sub-caliber projectile in a
bore for firing. The sabot normally disengages from the projectile
shortly after it exits the muzzle, falling to rest a short distance
in front of the gun.
SAAMI:
Sporting Arms and Ammunition Manufacturers Institute.
Seating
Depth: The depth to which the base of a given bullet is
seated below the case mouth.
Sectional
Density: A bullets weight, in pounds, divided by its diameter
in inches squared. High sectional density is essential to producing
a good ballistic coefficient and deep penetration.
SEE:
Abbreviation for Secondary Explosive Effect. SEE is a condition
which can occur when slow-burning powders are used at greatly reduced
charge weights (poor loading density). Rather than burning in a
normal fashion, the powder detonates, as though it were a severe
overload. Also known as a “pressure excursion.”
Selective
Fire: The capability of some automatic weapons to fire
in either the automatic or semi-automatic mode at the firer’s
discretion. These weapons normally have a switch or selector lever
to facilitate the operator’s choice.
Shell
Holder: The piece of a reloading press which holds the
base of the case during the reloading process. Shell holders are
generally removable, allowing one press to reload a wide variety
of cases by changing to the appropriate one.
Shoulder:
The sloping portion of a cartridge case, located between
the neck and the case body.
Single-Base:
Any smokeless propellant which uses nitrocellulose as its only explosive
base. Refer to: Smokeless Powder, and Double-Base.
Slam
Fire: A slam fire is an accidental discharge that occurs
during the feeding cycle, with no action on the part of the shooter.
Most frequently associated with Service Rifles in combination with
poorly assembled ammunition. The most common cause in handloaded
ammunition is a high primer, improperly set head-space (insufficient
resizing) or a combination of both. This is an extremely serious
condition that can destroy the rifle and injure the shooter.
Smokeless
Powder: A propellant powder, composed primarily of nitrocellulose
(single-base), or nitrocellulose and nitroglycerine (double-base).
There are triple-base powders as well, but they are not used for
reloading here in the U.S. Smokeless powder comes in several forms,
such as extruded tubular, ball, and flake.
Spherical
Powder: See: Ball Powder.
Spire
Point: A conically pointed bullet, as opposed to the more
common radiused ogival nose shape.
Spitzer:
Literally, German for “pointed.” In weapons terminology,
a spitzer refers to a pointed bullet.
Sub-Machine
Gun: An Automatic or Selective Fire weapon chambered for
a pistol cartridge. These weapons are normally compact, and intended
to be used at close combat ranges.
Swage:
To form metal under pressure. Normally done in a press, using a
punch or die.
SWC:
Semi-Wadcutter
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T
Terminal
Ballistics: The branch of ballistics which deals with the
projectiles impact on target.
Throat:
The unrifled portion of the bore immediately ahead of the chamber,
and before the leade. Also referred to as freebore.
Time
Of Flight: The time taken by a projectile to traverse two
points, or a specific distance. Time of flight is a critical factor
to a number of ballistic calculations.
Trajectory:
The arched path that a bullet follows in flight. Refer to: Bullet
Path.
Twist:
The rate at which a firearms rifling turns within the barrel. This
is normally expressed as the distance required for the projectile
to make one complete revolution. Depending on the origin of the
firearm, this may be written in inches or in millimeters; 1x12"
or 1x305mm.
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U
USPSA:
United States Practical Shooting Association
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V
Varmint:
A non-game animal such as coyotes, woodchucks, or prairie dogs.
In many states, varmints are not protected with regard to seasons
or bag limits.
Varminter:
Sierra’s designation for a line of frangible bullets, intended
for varmint shooting.
Varmint
Rifle: A rifle built specifically for varmint shooting.
Generally speaking, varmint rifles tend to be heavy-barreled, and
chambered for small-bore, flat-shooting cartridges such as the 223
Remington or the 22-250.
Velocity:
The speed of a projectile, usually expressed in feet per second
at a given distance.
VHA:
Varmint Hunters Association
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W
Wadcutter:
A bullet having a full-caliber flat nose, intended to cut a clean
hole in the target for easier scoring.
WCF:
Winchester Center Fire. Designates a center fire cartridge designed
or produced by Winchester. Examples would include the .30 WCF (.30-30),
.38-40 WCF, and .44-40 WCF.
Web:
The solid portion of a cartridge case between the primer pocket
and the powder chamber. The primer pocket and powder chamber are
joined by the flash hole, or vent.
Wildcat:
A non-standard cartridge or chambering. While the distinctions are
somewhat blurred, “wildcat” generally refers to a cartridge
for which factory chambered guns and factory loaded ammunition has
never been produced.
Windage:
Lateral correction of a firearms sights, to compensate for the projectiles
deflection by wind or drift.
Work
Hardened: To have changed the grain structure of a metal
by repeatedly stressing it. In cartridge cases, work hardening most
frequently occurs in and around the neck area, from the stresses
of repeated firings and resizings. This causes brittleness, and
leads to cracking and splitting of the case.
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X
X-ring:
The small center scoring ring in a target. The numerical value of
a shot in the x-ring is the same as the highest scoring ring on
the target, but is used to break ties.
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Y
Yaw:
The rotation of a bullet at an angle (usually very slight) to its
line of flight. Some yaw is almost always present when a bullet
is fired, but this usually dampens out within 200 yards if the bullet
is properly stabilized and well balanced.
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Z
Zero:
The adjustment of a firearms sights in order to obtain impact at
a desired point in relation to a specific point of aim, at a given
range.
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