The mechanism by which the rifle is loaded and fired, also covering the
withdrawal and expulsion of the fired round.
A weapon which will continue to load and fire so long as the trigger is
pressed and there is ammunition available in the feed system.
Noted as C, this term is a mathematical ratio between the bullet’s
sectional density and its coefficient of form, a construct originally
designed around a "standard" bullet form.
The study of projectiles in motion, to include many aspects, such as
extreme range and trajectory, as well as energy ratings from muzzle to
termination of flight. Exterior (also external) ballistics treats the
bullet after it leaves the muzzle. Interior or internal ballistics deals
with the bullet in the rifle from primer detonation to bore travel.
For our purposes, the mortise in the rifle stock which contains the
barrel and action of the rifle.
The cartridge case which has a band ahead of the extractor groove is a belted
case. The band or belt is generally a feature of the so-called magnum
cartridge. The band is used as the headspace gauge in the belted round.
Also, the wise reloader uses the belt as a gauge to measure pressure,
miking the belt after one firing and then miking again after consequent
loads to inspect for further expansion. Expansion across the belt
indicates a condition of high pressure (as well as possible brass
A notch cut in the weapon’s firing pin, striker or other component,
into which the sear engages to hold the component ready to fire.
System of operation analogous to blow-back but in which the bolt is
fixed and the inertia of the barrel at the moment of firing, the
cartridge in place. Breech pressure then forces the barrel forward to
open the breech.
Also boat-tail, or BT. A bullet with a tapered heel. The shape of the
boattail bullet aids its flight in the atmosphere, and boattails will
usually show a higher retained velocity at long range over flatbase
bullets of the same caliber and weight, all other things, such as
profile, being equal. However, in many practical aspects, the boattail
is not a distinct advantage, such as in the short- to modest- range
That part of a weapon which closes the breech; it may also perform the
functions of loading and extracting, and often carries the firing pin or
Breech closure of a small arm by means of a hand-operated bolt moving in
prolongation of the weapon’s axis. May be a ‘turnbolt’ in which
the bolt is pushed forward and then turned down to lock, by means of a
handle; or a ‘straight pull’ in which the manual action is a simple
to-and-from movement and the bolt is turned and locked by cam action.
A component which supports the bolt in its movement and generally
contains the means of rotating or otherwise locking it.
The interior of a weapon’s barrel, from the face of the bolt to the
muzzle, including both the chamber and the rifled portion.
A means of matching the sight picture with alignment of the bore. This
is accomplished by securing the rifle, looking through the bore,
"aiming the bore" at a target, and then adjusting the sights
until they are "looking" in the same place. In addition, a
bore sighter (also called a collimator) may be used, which is an optical
device that attaches to the muzzle of the rifle. Again, the sights are
adjusted to match the direction the bore is pointing to. Bore sighting
aids in getting that first shot "on the paper." By firing
first rounds from an unsighted rifle at very close range, much the same
advantage is realized.
A method of ammunition supply in the form of a metal or plastic box,
either detachable from the weapon or integral with it, below, above, or
to one side of the weapon. The cartridges are held inside the box and
impelled to the magazine mouth by a spring.
That portion of the rifle barrel which will contain the load, be that
load a cartridge or, in the case of a muzzle-loader, a powder charge and
A resilient component at the rear of an automatic weapon against which
the bolt or breech-block comes to rest after recoil. It absorbs some of
the recoil energy and assists in controlling the rate of fire. The
resilience may be due to springs, rubber, oil, or pneumatic media.
Colloquial term for a rifle in which the mechanism is set well back in
the stock so that the end of the receiver is against the firer’s
shoulder. This design permits the use of a full-length barrel in a
weapon which is shorter overall than one of conventional stocked shape.
That part of a shoulder arm which rests against the firer’s shoulder
and transfers the recoil force to his body.
The diameter of the interior of a gun barrel, defined as the diameter of
a cylinder which will fit inside the lands of the rifling. More
commonly, the diameter as measured from the top of one land to the top
of the opposite land.
Simply, a short rifle. The Model 94 carbine, for example, wears the
20-inch barrel, while the original rifle had a 26-inch barrel. It is not
incorrect to call a short-barreled rifle a rifle, however. But when a
reference to "carbine" is made, one knows that a shorter rifle
is being spoken of.
A unit of ammunition, consisting of a cap, cartridge case, propelling
charge and bullet. Also called a ‘round’ of ammunition.
Distance between the face of the bolt and the rear of the chamber when
the breech is closed. A critical dimension, since if it is insufficient
the bolt will not close and if it is too great the cartridge may set
back on firing and burst.
The rearward portion of the barrel which has been reamed, using a
specific reamer to create a specific cartridge dimension. The cartridge
itself fits into this section of the barrel for firing, held there by
the breech. That portion which lies ahead of the neck portion of the
chamber is called the leade or throat. Free-bored chambers have more
leade than standard chambers.
A lever or switch which allows the firer to select single shots or
automatic fire in certain types of weapon. Also called a ‘selector’;
may be combined with the safety catch.
A metal or plastic frame in which cartridges are held and from which
they can be loaded into the magazine of a weapon. The loaded charger is
positioned opposite the magazine and the cartridges are swept from the
charger into the magazine by thumb pressure. Common on bolt-action
rifles, occasionally found on automatic pistols and rifles.
A device used to calculate the velocity of a projectile. Modern
chronographs also allow the gathering of other data, such as standard
deviation from the mean velocity, extreme spread, highest velocity in
the string, lowest velocity in the string, and an average velocity,
rather than one simple velocity statement.
A metal frame in which cartridges are held and from which they are
loaded into the weapon’s breech. Differs from a charger in that
the loaded clip is inserted into the magazine, the cartridges are
removed from it one at a time as they are loaded, and the empty clip is
usually ejected as the last cartridge is removed. The clip forms an
integral part of the feed system; without it, the weapon cannot be used.
Found on bolt-action rifles, notably the Garand.
Device attached to, or forming part of, the muzzle of a weapon and which
diverts some of the escaping gas upwards or to one side so as to counter
the tendency of the gun muzzle to rise or swing during automatic fire.
The slack which must be taken up before the trigger disengages the sear
is called creep. A military-type or two-stage trigger may have
intentional slack and this slack is not generally referred to as creep,
whereas a trigger which is supposed to activate directly following
pressure from the pad of the finger but which has slack is known as a
trigger with creep in it.
The very last portion of the muzzle of the rifle, sometimes indented or
recessed to protect the rifling.
The theoretical rate of fire of an automatic weapon assuming a
continuous and infinite supply of ammunition – i.e., disregarding the
need to change magazines or belts.
The series of operations necessary to cause a weapon to fire on round
and return to a state of readiness. May be performed by hand or by an
automatic mechanism. It consists of:
1 Chambering the round
2 Closing and possibly locking the breech
4 Unlocking and opening the breech
5 Extracting the spent case
6 Ejecting the spent case
7 Cocking the firing mechanism
8 Feeding the next cartridge into place
Not all of these
functions may be present; e.g., a blowback weapon does not perform
unlocking and locking, a caseless weapon does not perform extraction and
ejection, and they may not be in the order given - e.g., cocking can
take place before extraction – but the entire cycle must be followed
by any small arm.
A mechanism in self-loading weapons which disconnects the trigger from
the firing mechanism after each shot. It can only be reconnected by the
firer releasing the trigger. It prevents a semi-automatic weapon firing
in the automatic mode. In selective-fire weapons it is thrown out of
action by the selector or change-lever.
A pistol firing mechanism which permits firing in either of two ways;
either by manually cocking the hammer and then releasing it by trigger
pressure, or by pulling through on the trigger so as to cock and release
To fire the rifle without ammo, as in practice. Insure that no damage is
done during dry-firing by using a snap cap to protect the firing pin,
bolt face, etc. Top
Device, generally spring-loaded, which expels the cartridge or the fired
cartridge case from the action after it has been extracted.
A claw-like device which removes the empty cartridge case from the
chamber of a weapon and presents it to the ejector.
That portion of the operating cycle of a weapon in which the cartridge
is removed from the ammunition supply and loaded into the chamber.
The expansion of a cartridge case, upon firing in the chamber, to a
dimension different from the original. For example, a standard 30-30
round fired in the 30-30 Improved chamber expands the walls of the case
so that they are much straighter, also creating a sharper shoulder.
Attachment to the muzzle of a weapon which cools the emergent propellant
gas so that it does not cause flash or flame when meeting the outside
Muzzle attachment intended to conceal the muzzle flash from the firer
when firing in poor light to maintain pupil dialation for night vision.
It can also act as a flash eliminator but is not so efficient in this
(1) The spring-driven platform in a weapon magazine upon which the
cartridges rest. (2) A spring or mechanically driven arm in the magazine
of a clip-loaded weapon which forces the rounds up in the clip and
presents them to the loading mechanism.
Removing material from the stock so that the barrel isn't touching any
part of the gun except for the receiver.
The use of a synthetic substance to form a barrel channel and/or a seat
in the stock for the action. New compounds are stronger than ever, and
easier to use. Also good for repair and strengthening of specific areas
of the stock.
Spiral cuts in the bore of a weapon which form the rifling and so impart
spin t the cullet. The uncut portion between grooves are the ‘lands’.
The number and form of the grooves, and the degree of curvature, depend
on the weapon, the ammunition, and the designer’s preferences.
A delay in ignition. Unlike a misfire, the hangfire does go off;
however, the rifle does not fire immediately. Associated primarily with
muzzle-loaders, especially flint-locks, but can occur in a cartridge as
That distance as measured from the bolt face of the rifle to that point
in the chamber where forward progress of the cartridge is halted. In a
rimmed cartridge, this distance is taken from the bolt face to the end
of the rim itself. In a belted magnum, the belt is used to gauge
headspace. On a rimless cartridge, the shoulder is used to mark
headspace distance. Gauges are used by the gunsmith to check the
headspace in a rifle. These are Go and No-Go gauges, sometimes a
"field gauge" as well. The Go gauge should allow the bolt to
close down easily. The bold should not close on a No-Go gauge. It will
close snugly on a field gauge. If the bolt of the action (and this
applies to lever action, semiauto, and pump guns, as well as bolt-action
rifles) will close on a No-Go gauge, that indicates excessive
headspace and the condition must be corrected.
The vertical movement of a gun barrel at the instant of firing. It is
related to the rigidity and mounting of the barrel and is not generated
by recoil; it is a constant value for any given charge and projectile
combination and can be compensated for in the sights.
Loss of bullet stabilization, causing the bullet to tumble end over end,
all gyroscopic effect in keeping the bullet point-on having been
The interior surface of a gun barrel between the grooves.
Metal used in the manufacture of small arms bullets and bullet cores.
Usually mixed with a small amount of antimony to give the correct
A deposit of lead left in the rifling grooves of a firearm after
prolonged firing of lead bullets. Eventually has a deleterious effect
upon accuracy if not removed and is the reason for the adoption of
jacketed compound bullets.
Term referring to a condition arising when the chamber of a revolver is
not perfectly aligned behind the barrel. As the bullet passes from the
chamber to the barrel, one side will strike the edge of the barrel which
will ‘shave’ a thin layer of metal from the bullet. This affects
balance and therefore accuracy; the metal shaving also tends to jam the
In modern terminology, the elapsed time from the release of the sear due
to activation of the trigger to the actual impact of the firing pin upon
the primer. A fast lock time is desirable.
A feed system for a firearm in which cartridges are stored in an
integral or attachable carrier, from which they are fed into the weapon
by spring or other agency.
MRT is the highest point in the parabola that the bullet reaches from
muzzle to point of impact at the target. Since the bullet must arc
upward from the muzzle in order to strike a distant target, it does
climb above the line of sight. How high it must climb to reach a given
distance is the MRT.
Specifically, one sixtieth of one degree, but for shooting purposes a
minute of angel consists of an inch at 100 yards, two inches at 200
yards, three at 300, and so forth. A rifle capable of minute-of-angle
accuracy will group its bullets into an inch center to center at 100
yards, two inches center to center at 200, three at 300, etc.
In the misfire, as opposed to the hangfire, the round does not go off at
all after the trigger is pulled. Sometimes a dead primer is the cause.
In muzzle-loaders, misfires often result from lack of flame reaching the
main charge in the breech.
The front end of the gun barrel, from which the projectile emerges.
A device fitted to the muzzle of a weapon and designed to deflect some
of the emergent gas and direct it against surfaces so as to produce a
pull on the muzzle and thus reduce the recoil force. Not widely used on
small arms, since the gas diverts sideways and increases the blast and
noise level to the firer and his companions.
A device which generally slips onto the shaft of the cleaning rod, its
function being to keep the rod centered in the rifle bore so that the
rifling, especially at the muzzle, is not scraped.
The speed at which the bullet leaves the muzzle of the gun. Also
referred to as ‘Vo’, the Velocity at zero distance from the weapon.
Expansion of the projectile in the bore due to reaction of gas pressure
and inertia of the bullet. Also used to designate the expansion of the
cartridge case as gases exert pressures which force the case to meet
with the walls of the chamber. Also known as "bullet upset" in
In reloading, the dent which appears in a cartridge case due to
excessive lubrication being trapped between the case and the walls of
the resize die.
A bullet which has a band between the rear and forward parts of the
projectile. This band prevents mushrooming of the projectile past a
given point. It also prevents separation of bullet core from bullet
jacket upon impact and during penetration of the missile.
The deterioration of the metal of a rifle due to rust. Used rifles may
have "pitted bores," meaning the bore is pockmarked with
erosion caused by metal deterioration.
The body of a weapon; the casing inside which the bolt operates and to
which the magazine and barrel are attached.
Rearward movement of the barrel or weapon due to reaction against the
forward ejection of the bullet. Recoil is a phenomenon explained by
Newton’s Third Law of Motion—every action has an opposite and equal
reaction. If the rifle and the bullet were of the same mass, both would
gain the same velocity after firing. Since the rifle is far heavier than
the bullet, it is the bullet which speeds away from the rifle. However,
the rifle does come back toward the shooter, "kicking" him.
The attributes of recoil include, aside from rifle weight, the weight of
the powder charge, weight of the bullet, and velocity of the bullet.
Spring in an automatic or self-loading weapon which cushions the
rearward movement of the bolt and returns it to the forward position.
Spiral grooves cut into the interior of a gun barrel so as to spin the
bullet and thus impart gyroscopic stabilization to it. The degree of
curvature depends upon the weight and length of the bullet fired from
A cartridge with priming mixture distributed around the rim of the case.
The 22 rimfire is a good example.
The Sporting Arms and Ammunition Manufacturer’s Institute, an
organization responsible for the standardization of measurements in the
industry, including chamber dimension and other important specifications
From the French, this term was used to denote a wooden shoe. In early
shooting, the sabot was wooden. Today, the sabot is plastic. It is a
heavy-duty device which fits around a bullet. Specifically, the sabot is
used in modern ammo in order to fire a 22-caliber bullet from a
30-caliber bore. It can, and may, be used from many other calibers as
well. Remington Accelerator 30-30, 308, and 30-06 caliber ammo uses the
sabot, all three firing a 55-grain, 22-caliber bullet. The plastic sabot
simply falls away from the bullet and the bullet speeds to the target.
It is a good way of turning a larger-bore rifle into one capable of
firing smaller projectiles. The above Accelerator for the 30-06 shoots a
55-grain, 22-caliber bullet at about 4,000 fps MV.
A bar or metal piece which translates the activation of the trigger into
the dropping of the firing pin. The sear is disengaged by the trigger
pull and then the hammer or plunger is allowed to fall, thus firing the
This is a ratio. It is the relationship between a bullet’s weight in
pounds divided by the square of the bullet’s diameter in inches. The
result is a number in decimal form. The higher the number, the greater
the sectional density of the bullet. For example, a bullet of .226
sectional density compares poorly with a bullet of .286 sectional
density, the latter handling the ravages of the atmosphere better,
provided both bullets have similar profiles.
Descriptive of a weapon which, at the firer’s choice, can be set to
fire single shots, automatic fire or specific-length burst, according to
A firearm which, for a single pressure of the trigger, fires a round and
then reloads. The trigger must be released and pressed again to fire
Weapon which fires one round, re-loads, and requires another pressure on
the trigger to fire again. Synonymous with ‘self-loading’.
The distance between front sight and rear sight on a rifle wearing
metallic sights. Open sights and aperture sights pertain.
Device attached to the barrel of a weapon and which traps the emergent
gas and forces it to pass round a series of baffles, cooling it and thus
reducing its volume, so that it emerges at low speed and does not,
therefore, make much noise. The silencer also has holes bored in the gun
barrel so as to bleed off propellant gas behind the bullet and reduced
its speed to below that of sound, so avoiding a sonic crack due to the
A pointed bullet as opposed to a round- or flat-nosed bullet.
The channel in the bullet mold through which the molten lead is poured
to form a projectile. Also the tiny projection of lead on the projectile
left where the sprue plate cut the sprue away from the missile. This
small projection is supposed to be loaded upward in the muzzle-loader
for round-ball-shooting rifles.
Similar to a silencer insofar as it baffles the emergent gas, but does
not bleed gas from behind the bullet. Therefore it only silences the
muzzle discharge and not the bullet’s sonic wave. If used with
subsonic ammunition is effectively a silencer.
Pistol-calibre selective-fire or automatic weapon, magazine fed, fired
from the shoulder or hip, used for close-range combat.
Bullets, including round ball, made by forcing lead into a die which
sizes the projectile—as opposed to creating bullets with a mold and
molted lead. Round balls so created have no sprue. The round balls
currently produced by Hornady and Speer are of the swaged type and are
The arc described by the bullet from muzzle to destination. This arc is
a parabola, a specific curve. The path the bullet takes is its
trajectory. In sighting-in, the idea is to take best advantage of the
bullet’s trajectory potential.
Effectively, an electrical means of calculating the pressure generated
in the breech of the rifle. A specific quartz crystal is used. These
crystals emit an electrical response to pressure. Pressure on the
crystal results in more response for more pressure. A device transfers
the chamber pressure to the crystal and a readout is translated into psi,
In rifle shooting, the speed of the projectile, measured in feet per
second (fps). Derived from a chronograph.
The highest point of the bullet’s trajectory.
Adjustment of a weapon sight to right or left to compensate the effect
of a cross-wind on the bullet. Horizontal movement of sights, as opposed
to elevation. Also the space between the projectile and the bore in the
muzzle-loader, which space is taken up by the patch.
That point at which the rifle is sighted-in to deliver its group. A
rifle "zeroed" for 200 yards prints on the bull’s-eye at 200
yards. Zeroing is the adjustment of a weapon sight so that the bullet
will strike the point of aim at some specified distance.