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COMPENDIUM OF TERMINOLOGY A B C D E F G H I J K L M N O P Q R S T U V W X Y Z The most complete compendium related to airguns on the web! A Accuracy The
ability of an airgun to consistently Group all its
shots close together at a given distance under optimal conditions. Accuracy
does not take into account human error or environment conditions. B Barrel Time The
time elapsing between the bullet starting to leave its seat until exiting
the muzzle. Barrel Time and Lock Time are significant,
as they can greatly affect the Point Of Impact. Bead Sight The
cylindrical top part on some front sights. Bedding The
fitting of the action with the stock. Benchrest A
specifically designed support, e.g. a table (rest). Bipod A two-legged
support attached to the fore-end of the stock. Bluing The chemical
treatment to color ferrous metal parts in various shades of blue or black. Breaking
In A Barrel Process of initial use of a factory-new bore by
firing a certain number of shots and cleaning frequently. Breaking In the
barrel should be done before trying to attain good Groups.
500 to 800 pellets are usually sufficient. Bullet Drop The
measure of a projectile's drop after the projectile crosses the line of
sight for the second time; beyond the zero or sighted-in range. C Checkering A
diamond-like pattern for ornamentation or improved gripping. See also Stippling. Cheekpiece A
raised part of the side of the stock of a shoulder-arm. CO2 Chemical formulae
for carbon dioxide. Precharged pneumatic guns use a sear that hits a valve
releasing pressurized CO2 into the barrel and propels the bullet. CO2 is
in a fluid state when pressurized. D Diesel Effect A
detonation inside the pressure chamber when grease evaporates and the resulting
gases ignite, caused by the heating of the compressed air in conjunction
with the heat the piston seal generates while moving along the chamber
walls. The Diesel Effect is unpredictable and dreaded, as its resulting
excess recoil can easily damage scopes, even those which are designed to
take the Spring Piston-specific type of
Recoil. Drift Lateral
movement of a bullet away from the line of bore, caused by its rotation
on its axis, in the direction of the rifling twist. With airguns, drift
is not a significant value. Drop at Comb The
vertical distance from the line of sight to the comb, or Monte
Carlo, 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. Drop at Heel The
vertical distance from an extended line of sight to the heel of the stock. E F Foot Pound (ft/lbs) Unit
of measurement for Energy, being the amount of
energy required to lift a one pound weight one foot. G Grain (gr.) Measure
of weight applied to bullets. 1 grain equals 0.0648 grams. Grooves Grooves
and Lands make the Rifling
of a barrel. The grooves are the lowered areas between two lands. Group A cluster
of bullet holes made by the same airgun/pellet combination, formed from
numerous shots fired at a target using the same point of aim, for checking
accuracy. A 10-shot group provides useable statistics. Group Size Usually measured center-to-center,
the maximum distance between the centers of the two farthest shots in a
Group. H J L Length Of Pull The
distance from the vertical center of the trigger to the vertical center
of the butt plate or Recoil Pad. Lock Time The
time elapsing between the trigger release and a.) on Pneumatic
and CO2 airguns: the release of pressurized gases
into the barrel; b.) Spring Piston airguns:
the piston reaching the fore end of the pressure chamber. Since no one
can hold an airgun absolutely steady while shooting, the longer the Lock
Time, the higher the chances to inadvertently move the weapon before the
bullet has actually left the barrel. The Recoil
can also greatly affect the Point Of Impact
due to the Lock Time and Barrel Time, Spring
Piston airguns have the highest Lock Time, one of the reasons why they
are excellent training weapons, as they force the shooter to pedantically
apply the rules of marksmanship. M Mid Range
Trajectory In its parabola-shaped path, the highest vertical
distance reached by a bullet above the line of sight. Mil Angular unit
of measurement used to estimate distance and size: 1 Milradian is 1/1,000
of the distance; 1 meter at 1,000 meters; 1 yard at 1000 yards. 360 degrees
consist of 6,400 Mils by military definition, 6283.2 mathematically. Minute Of Angle
(MOA) Angular unit of measurement used to describe the Accuracy.
One MOA equals 1/60th of a degree (21,600 minutes in a complete revolution)
and subtends 1.0473 inches at 100 yards, or, as a rule of thumb, 1 inch
at 100 yards. 1 Mil contains 3.44 MOA. MOA See Minute Of Angle. Monte Carlo A
stock with a raised comb. N Ocular Also
known as the eyepiece. The magnifier lenses between the optical system
and the eye. Off-hand Position A
position in which the shooter stands upright, not resting the rifle or
his body on or against any supporting object. Open Sight Rear
sight of traditional open-topped V-notch or U-notch. P Pneumatic Precharged
air tank system. The sear hits a valve that releases pressurized air into
the barrel and propels the bullet. Point Blank The
shooting distance to which one can hit a specified target area without
modifying the Point Of Aim. The Mid-Range
Trajectory and the Bullet Drop will both
fall within the specified area. Point Of Aim (POA) The
point on a target on which the sights are optically aligned. Point Of Impact
(POI) The point where the bullet hits. 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/pellet
combination is "zeroed" or "sighted in" at that range. Probability
Of Hit (POH) Refers to the chance (0 to 100%) that a given
round will hit the target at a given range, depending mainly on the gun's
Accuracy. Q Recoil The
rearward thrust caused by the propulsion of the piston or the bullet. Spring
piston airguns have also a very aggressive and powerful forward kick, caused
by the piston hitting the front end of the pressure chamber. It is this
second forward snapping that can damage even high-quality riflescopes.
The recoil can have be devastating to the system when the airgun diesels.
See also Diesel Effect. Recoil Pad A
rubber or leather pad at the end of the butt to absorb the Recoil. Reticle In
scopes, the element which is optically referred to the target, consisting
of straight or tapered cross-hairs, dots, or other marks used to determine
the Point Of Aim, size of, or range to the
target. Rifle Cant Any
leaning of the rifle to one side from a vertical position during firing,
increasing the potential for misses, especially at longer ranges. Rifling Twisted
Lands and Grooves are placed
into a barrel to impart spin on the bullets that pass through it. Rifling Pitch or
Rate Of Twist is the distance the Rifling
needs to spin down the barrel for it to complete a single revolution. S Scope Mounts Devices
for mounting a scope to a rifle. Scope Rail Machined
grooves or rail to which the the scope mounts
are attached. Sight-in The
sight adjustments to get the Point Of Aim
to coincide with the Point Of Impact at
a preselected distance. It is bets done by firing 3 to 5 shot groups between
each adjustment. Silencer A
device designed to muffle the sound of the discharging of pressurized gases
exiting the muzzle. See also Suppressor and
Sound Moderator. Spring Piston The
mechanical part within the pressure chamber that moves forward under steel
spring or gas spring pressure, compressing the air in the chamber and pushing
it into the barrel. The piston front consists of a sealing. Suppressor A
device designed to nearly totally absorb the sound of the discharging of
pressurized gases exiting the muzzle. It can also be an integral assembly
with the barrel. See also Silencer and Sound
Moderator. Sound Moderator
A device designed to moderate the sound of the discharging of pressurized
gases exiting the muzzle. See also Suppressor
and Silencer. Stippling A random
pattern of stipples for improved gripping. See also Checkering. Swivel The
attachment hook for the sling to the stock. T Trajectory The
path of a projectile in flight. As gravity causes the bullet to drop from
the moment it exits the muzzle, its trajectory is always curved in the
shape of a parabola. Transfer Port A
port hole, an air-tight connection between the pressure chamber/air reservoir
and the barrel, through which the gases travel prior to propelling the
pellet. Trigger Pull The
force that must be applied to the trigger for it to release the sear. A
good Trigger Pull must be appropriately light, and the release must be
a clean, sharp snap. Turret The
housing for the adjustment of windage and elevation dials on riflescopes.
U W X NOTE Terms and descriptions are related
to air guns
Accessory Rail A
metal track for mounting hand stops or slings, installed in the fore-end
of the stock.
Ballistic Coefficient A
measure of how a projectile decelerates during its flight through the air
due to drag. The ballistic coefficient is an important and useful concept
that is used for ballistics calculations. The smaller the BC of a bullet,
the greater its air resistance. The higher the BC, the more aerodynamic
the bullet.
Caliber (cal) The numerical value of an
approximation of the bullet diameter in inches or millimeters.
Deflection The change in the path
of the projectile due to passing through a medium or caused by wind.
Energy Kinetic energy of a projectile.
See also Foot-Pounds and Joules.
Feet Per Second (ft/s) Unit
of measurement of the speed a projectile flies with. Also see Meters
Per Second and Velocity.
Girth The smallest circumferential dimension
at the pistol grip of a stock.
Hand Stop A device attached to the
stock's fore-end to prevent the supporting hand from sliding forward.
Joule (J) Unit of measurement for Energy,
being the amount of energy required to lift a one pound weight about nine
inches.
Lands Lands and Grooves
make the Rifling of a barrel. The lands are the
raised areas between two grooves.
Meters Per Second (m/s) Metrical
unit of measurement of the speed a projectile flies with. Also see Feet
Per Second and Velocity.
O
Objective The optical lens in riflescopes
that receives light and forms the primary image. The image is magnified
by the Ocular.
Parallax The apparent movement of
the target in relation to the Reticle when the
shooter moves his eye in relation to the ocular lens. When the target's
image is not focused on the same focal plane as the riflescope's reticle,
a parallax error is the result. For varmint shooters, improper Parallax
adjustment can easily make the difference between a hit and a miss.
R
Rate Of Twist or Rifling
Pitch is the distance the Rifling needs to
spin down the barrel for it to complete a single revolution.
Scope Creep An unwanted effect
where the Scope Mounts creep along the Scope
Rail. During the firing cycle of Spring
Piston powered gun, the piston bangs into the front end of the compression
chamber, making the entire gun to snap forward violently. There are systems
that eliminate scope creep for good.
Terminal Velocity The speed
of the projectile upon impact with the target.
V
Velocity The speed of a projectile,
measured in either Feet Per Second or
Meters Per Second.
Windage The adjustment on the scope
or open sights to compensate for horizontal Deflection
of the bullet.
Y
Z
Zero The range at which the Point
Of Aim and the Point Of Impact are
identical. See also Bullet Drop, Trajectory.
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