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ACCESSORY RAIL: A metal track intended for mounting hand stops or slings.

ACCURACY: The ability of an airgun to consistently group a serious of shots within a diameter as small as possible, at a given distance under optimal conditions. Accuracy does not take into account human error or environment conditions such as wind and elevation.

AIR RIFLE: An airgun (also air rifle or air pistol) is a rifle or pistol that fires a projectile by means of compressed air or other gases. Most airguns use metallic projectiles as ammunition.

AIR RIFLE SCOPE: Designed as a rifle scope but sturdy enough for double recoil of a spring piston air rifle and normally for parallax within 10 yards


BALLISTIC COEFFICIENT: A measure of how a projectile decelerates during its flight through the air due to drag. It is an important and useful concept that is used for ballistics calculations. The higher the BC, the more aerodynamic the pellet will be, and the smaller the BC of a pellet, the greater its air resistance.

BARREL TIME: The time elapsing between a pellet starting to leave its seat exiting the muzzle. Barrel Time and Lock Time are significant, as they can greatly affect the Point-0f-Impact (POI).

BENCHREST: A specifically designed support, e.g.a table (rest)

BIPOD: A two legged support attachment to the fore-end of the stock.

BLUING: The chemical treatment to color ferrous metal parts in a various shades of blue or black.


CALIBER: The numerical value of an approximation of a pellet diameter, measured in inches or millimeters.

CHEEK PIECE: A rasied part of the side of a stock of a should-arm.

CHOKE: The slightly narrow bore diameter towards the muzzle, about 1 to 1.5 inches long. The pellet is sized down before it exits the barrel to ensure each one does so in exactly the same way.
CO2: The chemical formula for Carbon Dioxide. CO2 is in a fluid state when pressurized.

C02 Gun: Airgun powered by Carbon Dioxide (CO2) from a compressed liquid source. CO2 boils from a liquid state to a gas as the airgun is charged. Gaseous C02 propels the projectile when the air gun is fired. CO2 typically produces 500psi at 32F (0C) and 1000 psi at 85F (29C), which provides a typical operating pressure of 750psi in airguns.

COATED OPTICS: Coating on lens surfaces reduce light loss and glare due to reflection for a brighter, higher contrast image with reduced eyestrain.


(a) COATED: A single layer on at least one lens

(b) FULLY COATED: A single layer on all air-to-glass surfaces.

(c) MULTI-COATED: Multiple layers on at least one lens and all surfaces are coated at least once.

(d) FULLY MULTI-COATED: Multiple layers on all air to glass surfaces. \

COMPETITION/MATCH GRADE AIRGUN: A modern airgun for precision and shooting balance. This is the class of airguns used in Olympic competition. These airguns are capable of delivering exceptional accuracy with modest power.


DEFLECTION: The change in the path of a projectile due to passing through a medium or can also can be caused by wind.


ENERGY: Kinetic energy of a projectile. Measured n Foot/Pounds or Joules.

EXIT PUPIL: The size of the column of light that leaves the eyepiece of a scope. The larger the exit pupil is, the brighter the image. To determine the size, divide the objective lens diameter by the power.

EYE RELIEF: The distance a scope can be held away from the eye and still present the full field of view.


FEET PER SECOND (FPS): Unit of measurement of the speed a projectile flies. Also see Meters Per Second and Velocity.

FIELD OF VIEW (F.O.V.): The side-to-side meausurement of the circular viewing field or subject area. It is defined by the width in feet or meters of the area visible at 100 yards or meters. A wide field of view makes it easier to spot game and track moving targets. Generally, the higher the magnification is, the narrow the field of view will be.


GROOVES: Grooves and Land make the rifling of a barrel. The grooves are the lowered areas between two lands.

GRAIN: Measure of weight applied to pellets. 1 grain equals 0.0648 grams

GROUP: A cluster of pellet holes made by the same airgun/pellet combination, formed from numerous shots fires at a target using the same point of aim, for checking accuracy. A 10-12 shot group provides useable statistics.

GROUP SIZE: Commonly measured center-to-center, the maximum distance between the centers of the two farthest shots in a group.


HAND STOP: A device attached to the stock’s fore-end to prevent the supporting hand from sliding forward.


IRON SIGHTS: A system of aligned markers used to assist in the aiming and excludes the use of optics as in a scope. Typically composed of two component sights, forward by metal blades: a rear sight mounted perpendicular to the line of sight and consisting of some form of notch (open sight) or aperture (closed sight) and a front sight that is a post, bead, or ring.

LANDS: Lands and grooves make the rifling of a barrel. The lands are the raised areas between two grooves.

LENGTH OF PULL: The distance from the vertical center of the trigger to the vertical center of the butt plate.

LOCK TIME: The time elapsing between the trigger release and the release of pressurized gas into the barrel on Pneumatic and CO2 airguns. Since no one can hold an airgun absolutely still while shooting, the longer the Lock Time, the higher the chances of inadvertently move the weapon before the pellet has actually left the barrel. Recoil can also affect the Point Of Impact due to the Lock Time and Barrel Time.


MAGNIFICATION (POWER): Riflescopes are often referred to by two numbers separated by an “X”. For example a 4x40, the first number is the power of magnification of the scope. With a “4X”, the object being viewed appears to be four times closer than we seen with the unaided eye.

4-16x50 scope

1. This means the scope has variable zoom capability.

2. In this case it ranges between 4 and 16x magnification through a 50mm wide view lens (objective lens).

METERS PER SECOND (m/s): Metrical unit of measurement of the speed a projectile flies with.

MID RANGE TRAJECTORY: In its parabola-shaped path, the highest vertical distance reached by a pellet above the line of sight.

MIL: Angular unit of measurement used to estimate distance and size. 1 Milradian is 1/1000 of the distance; 1 meter at 1000 meters; 1 yard at 1000 yards. 360 degrees consists 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

MUZZLE VELOCITY: The speed at which a projectile leaves the muzzle of the airgun.



OBJECTIVE: The optical lens in riflescopes that receives light and forms the primary image. The image is magnified by the ocular.

OBJECTIVE LENS SIZE: The second number in the formula (4x16) is the diameter of the objective or front lens. The larger the objective lens is and the more light that enters the scope, the brighter the image.

OCULAR: Also known as the eyepiece, are the magnifier lenses between the optical system and the eye.

OCULAR LENS: The lens closest to your eye.

OFF-HAND POSITION: A position in which the shooter stands upright, not resting the rifle or body on or against any supporting object.

OPEN SIGHT: Rear sight of traditional open-topped V-notch or U-notch.


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 miss situation.

PELLET 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.

PSI(Pounds per square inch): A measure of pressure. Metric: Pascal (Pa) or Kilopascal (kPa). 1 psi = 6894.7 Pa or 6.894 kPa.

PNEUMATIC: Pre-charged air tank system (PCP) The sear hits the valve that releases pressurized air into the barrel and propels the pellet.

POINT BLANK: The shooting distance to which one can hit a specified target are without modifying the Point Of Aim. The mid-range trajectory and the pellet drop will both fall within 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 pellet hits. By adjusting the sights, the point of impact can be made to coincide with the point of aim at a pre-selected distance; hence we say the rifle/sight/pellet combination is “zeroed” or “sighted in” at that range.

PRE-CHARGED PNEUMATIC (PCP): Pre-charged air tank system. The sear hits a valve that releases pressurized air into the barrel and propels the pellet.

PRECISION ADJUSTMENTS: The windage and elevation adjustments affect accuracy. Windage is the horizontal (left to right) adjustment, usually the side turret of the scope. Elevation is the vertical (up and down) adjustment, usually the top turret of the scope.

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.



RECOIL: The rearward thrust caused by the propulsion of the piston or the pellet. Spring piston airguns have a very aggressive and powerful kick, caused by the piston hitting the front end of the pressure chamber. It is this second forward snapping that can cause damage to high-quality riflescopes. The lack of recoil in Pre-charged airguns means riflescopes can be used without fear or damage often caused by the recoil of spring-pistol airguns.

RETICLE: In scopes, the element that 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 or the rifle to one side from a vertical position during firing, increasing the potential for misses, and especially at longer ranges.

RIFLE SCOPE: A riflescope indicates a pellet’s point of impact and makes distant targets and surrounding objects appear closer. A riflescope is recommended for safer, more accurate shooting in the field and on the range.

RIFLING: Twisted lands and grooves are placed into a barrel to impact spin on the pellet that pass through it.

RIFLING PITCH OR RATE OF TWIST: The distance needed for the rifling to spin down the barrel for it to complete a single revolution.


SCOPE MOUNTS: Devices for mounting a scope to a rifle or pistol.

SCOPE RAIL: Machined grooves or rail to which the scope mounts are attached. Airguns feature 11mm dovetail rails.

SIGHT IN: The sight adjustment to get the point of aim to coincide with the point of impact at a pre-selected distance. It is best done by firing 3-5 shot groups between adjustment.

SILENCER/SOUND MODERATOR: A device designed to muffle the sound of the discharging of pressurized gases exiting the muzzle.

SWIVEL: The attachment hook for the sling to the stock.


TERMINAL VELOCITY: The speed of the projectile upon impact with the target

TRAJECTORY: The path of a projectile in flight. As gravity causes the pellet to drop from the moment it exits the muzzle, its trajectory is always curved in the shape of a parabola.

TRANSFERPORT: A porthole, an airtight connection between the pressure chamber/air reservoir and the barrel, through which 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.



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 barrel.