GTA General Air Gun Glossary Of Terms

AAFTA - American Airgun Field Target Association, the governing body for field target in America.

Action - A group of moving parts used to cock, compress air (in some models), load, and fire an air gun.

Adjustable Objective - The adjustment on a riflescope that allows the parallax to be adjusted so that the target or quarry is in perfect focus. Typically this adjustment is on the front of the rifle scope and has distance marking on the adjustment bell.

Airgun - A gun which propels a projectile through its barrel by use of compressed air or carbon dioxide gas (C02). Gunpowder is not used in this type of gun.

Air Reservoir - The holding tube or bottle used for holding air under pressure for a precharged pneumatic airgun. Typically the reservoir resides in a tube under the barrel or in a removable bottle.

Break Barrel – Type of airgun that the barrel is released and pivots downward in order to load a round and to cock the spring/gas spring mechanism.

Breech - The rear end of the barrel where the pellet is loaded.

Bore - The inside of the barrel of a gun.

Caliber - The diameter of a projectile, the distance between the lands in a rifled barrel, or the bore diameter in a smooth bore barrel.

C02 airgun - A type of pneumatic air gun utilizing carbon dioxide gas (C02) or air that has been compressed and stored in a metal cylinder, or air that is compressed by an external air pump. This type of air gun allows the firing of multiple shots without recharging.

Detonation – When oil migrates into the air chamber of an airgun and is put under extreme pressure during the firing cycle, the oil will actually explode. Detonation can cause burning of the piston seal and/or breach seal. Detonation is identified by the loud pop (similar to the breaking the speed barrier pop) and by a trail of smoke from the barrel or breech. Excessive detonation is a sign of lubricant being present in the air chamber from over or improper lubing or from a damaged piston seal allowing lubrication to migrate into the air chamber.

Dieseling - When a spring piston airgun has excessive lube, and this lube ignites due to the heat caused by the rapid increase in air pressure during the piston compression stroke. This process is normal on a new or recently lubricated spring gun. Excessive dieseling can be cause for concern as seals and/or components can be damaged.

Disco – Benjamin Discovery PCP Air Rifle

Eye Relief - The distance behind a rifle scope's eyepiece at which you can see a full sight picture.

Field of View - The width of a rifle scope's sight picture at 100 yards or 100 meters. A wider field of view makes it easier to spot game and track moving targets.

Gas Spring – Type of power plant in an airgun that uses a nitrogen filled strut instead of the conventional coiled spring

Hold Over/Under - Changing the point of aim either above or below of the target (without adjusting the sights) to adjust for the trajectory of the pellet.

Kentucky Windage - Changing the point of aim either left or right of the target (without adjusting the sights) to adjust for wind effects on the pellet.

Lane - A shooting position/station in a field target competition.

Magnification - The power rating of a rifle scope indicated by the symbol "X". A 24X rifle scope makes the target appear twenty four times closer than it actually is.

Minute of Angle (MOA) - This is an angular unit of measurement which is approximately 1.1" at 100 yards. This term is typically used in defining the click adjustments on a rifle scope.

Mounts & Rings - Devices used to attach a rifle scope to a rifle.

MRod – Benjamin Marauder PCP Air Rifle

Muzzle - The front end of the barrel from which a projectile exits.

Nitro Piston – Trademark of Crosman series of gas spring powered airguns

PCP – Pre-charged Pneumatic Airgun

Pellet - A type of air gun projectile made from lead.

Pistol - A gun that has a short barrel and can be held, aimed, and fired with one hand.

Plinking - Informal, non competition shooting at a variety of fun targets.

Pneumatic Airgun - A type of air gun which utilizes the principle of stored compressed air or gas. Divided into two sub-categories: single stroke or multi-pump pneumatics and compressed C02/air pneumatics.

Point Of Impact (POI) - The place that the projectile (pellet) hits when the airgun is discharged.

Precharged Pneumatic (PCP) - an airgun that uses compressed air as the means of propulsion. Typically PCP guns are charged to 3000 psi from a SCUBA tank or hand pump.

Prod – Benjamin Marauder Pistol PCP Airgun

Rangefinding - Using the adjustable objective on a rifle scope to determine the distance to a target or quarry. While looking at the target, the adjustable objective is turned until the target is in clear focus. The distance is then read from the adjustable objective.

Rifling - Spiral grooves and lands in the barrel bore that provide a stabilizing spin to a projectile so that it will be more accurate in flight.

Sights - Mechanical, optical, or electronic devices used to aim a gun.

Single Stroke Pneumatic Airgun - A type of pneumatic airgun which uses one stroke of a lever to compress and store enough air in a reservoir or chamber for one shot.

Spring-Piston Airgun - An air gun which uses a manual lever or other device to cock a spring-loaded piston which compresses air at the instant of firing. The compressed air that propels the projectile is not stored in a reservoir prior to firing. This class/division includes gas ram and opposing piston types of guns.

Zero Shift - A movement of the point of impact at the Zero point after the airgun has been sighted in.

Airgun Rated (Scopes) - Can mean one of two things: 1)Built strong enough to handle a heavy recoiling spring gun, which recoils both rearward and forward, which is more harmful to scopes that high-power firearms. or 2)Built to focus down to closer ranges than a typical firearm scope, normally about 10 yards as a minimum.

BAR vs PSI (Air Pressure) - Two standards of measurement for pneumatic pressure. 1.0 BAR is equal to 14.5037738 PSI. So, 200 BAR x 14.5037738 is equal to 2900.75 PSI. To convert PSI back to BAR, divide by 14.5037738.

Foot Pounds (Ft/Lbs) - A way to measure energy based on the velocity and the weight of the ammunition used. To calculate, use the following equation:

Gas Ram - Similar to a spring gun in function, without the mainspring. A gas ram is a gas strut placed in the compression chamber of the rifle. Behind the piston is compressed air. When the airgun is cocked, the air is further compressed. When the airgun is fired the air expands and pushes the piston forward, compressing the air in front of the piston and thus fires the pellet.

M.O.A. - Acronym for Minute of Angle. Minute of Angle is defined as the distance of a line that is made from point A to point B of an angle of one minute of one degree at a distance of 100 yards. More simply stated, Minute of Angle is movement of 1 inch at 100 yards. A scope with 1/4" MOA will shift 1/4" of movement at 100 yards for every click of the turret. Target scopes have finer adjustments with 1/8" MOA, allowing for 1/8" of movement per click at 100 yards.

Moderator - A device designed to reduce muzzle report on an airgun by moderating the air released when firing.

Precharged - Any airgun that requires gas to be transfered to an onboard tank to generate its power.

Regulator - Device that steps the pressure in the air cylinder down to a lower level to maintain consistent pressure for the airgun to fire from. Often found on match grade rifles to ensure absolute consistency.

Side Lever – Type of airgun with the cocking mechanism (lever) mounted to one side of the receiver. The lever is pulled sideways to cock the power plant and to load the airgun.

Single Stage Trigger - Typical American hunting trigger that breaks upon application of pressure.

Two Stage Trigger - Small amount of take up is the first stage, coming to a complete stop. Second stage breaks and releases trigger with any further pressure.

Underlever - Any airgun where the cocking lever is seperate from the barrel and located beneath the barrel. Most run parallel with the barrel, but some are inside the stock.

Velocity - The speed at which the ammunition is being propelled. Normally calculated as Feet-Per-Second (fps).

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Rifle Scope Glossary Of Trmes

Adjustable Objective:

An adjustable objective is the dial around the objective end of the scope, or a knob on the left side of the turret housing that allows you to adjust your scope's parallax to a certain distance by moving these adjustments until a clear picture is perceived, and/or the marked corresponding incremental yardages are approximated to your target distance. The correct setting of an adjustable objective prevents the apparent movement between the reticle and the target when the shooter moves his head slightly off center of the rifle scope.

Airgun Scope:

Airgun scopes are specially designed to withstand the dual-recoil of spring piston airguns. Spring piston airgun recoil will destroy non-airgun rated scopes very quickly. Airgun scopes are usually sealed on both sides of the lenses and made stronger overall. They also have adjustable objectives to allow the shooter to use high magnification at short distances. Official airgun distances are 10 meters (33 feet), 25 feet, and 50 feet.

Coatings:

Microscopic coatings on the lens surfaces reduce light loss and glare due to reflection. Coated lenses offer a brighter, higher contrast image with less eyestrain. More coatings allow better light transmission, but it is very possible to have a scope with a single coating to greatly outperform a scope with multicoated lenses. It all depends on the quality of the coatings as well as the glass. Good quality does not come cheap. The following are accepted terms for coatings:

Coated: A single layer on at least one lens surface.

Fully Coated: A single layer on all air to glass surfaces.

Multicoated: Multiple layers on at least one lens surface.

Fully Multicoated: Multiple layers on all air to glass surfaces.


Click:

A click is one adjustment notch on the windage or elevation turret of a scope. One click will change ascope's point of impact ¼ inch at 100 yards. Some clicks are 1/8 inch and ½ inch.

Exit Pupil:

An exit pupil is the small circle of light that is visible in the ocular lens when you hold your scope (or binocular) at arm's length. The larger the exit pupil, the brighter the image that will be entering your eye. To find the exit pupil for your scope, divide the objective lens diameter in millimeters by the magnification. For example, if your scope is three power (3X), and your objective lens is 40 millimeters in diameter (40mm), divide 3 into 40 and it equals 13.33, which would be the exit pupil size diameter in millimeters.

Eye Relief:

Eye relief is the distance your eye must be from the ocular lens to still get a full field of view.

Field of View:

Field of view (FOV) is the area seen through your scope from right to left at 100 yards. As magnification is increased, FOV is lessened. As magnification is decreased, FOV is increased. For example, a typical 3X variable scope might have a FOV at 100 yards slightly over 30 feet, and at 9X, the FOV would be approx. 14 feet. A larger objective lens will not change these figures.

Hold Over/Under:

Hold over/under is the amount of point of aim change either above or below your target, without adjusting your scope, to adjust for the trajectory of your projectile.

Windage:

Windage is the amount of point of aim change either left or right of your target, without adjusting your scope, to adjust for wind effects on your projectile.

Magnification:

Magnification is the power rating of the scope, indicated by the symbol "X". A 12X (twelve power) scope makes objects seem twelve times closer than with the naked eye.

Maximum Point Blank Range:

The longest distance you can hold dead center in your kill zone and not be too high or too low for a hit in the vital area. Flatter trajectories and/or larger targets increase this range.

Minute of Angle:

Minute of Angle (MOA) is a unit of measurement of a circle, and is 1.0472 inches at 100 yards. This is usually called 1 inch at 100 yards. It is 2 inches at 200 yards, 5 inches at 500 yards, one half inch at 50 yards, etc.

Muzzle:

The muzzle is the front end of the barrel from which the projectile exits.

Objective Lens:

The objective lens is the lens closest to the object being viewed. It is measured in millimeters for diameter. A larger objective lens allows more light to enter the scope. In a three to nine by forty (3-9X40) scope, the 40 is the objective lens size.

Ocular Lens:

The ocular lens is the lens closest to your eye.

Parallax:

Parallax is the apparent position of the reticle on the target image at different ranges. This is most visible when the eye is moved outside the center of a scope while viewing a target at other than the standard distance at which the scope has been preset to be parallax free. Most riflescopes without adjustable objectives are set at 100 or 150 yards. Rimfire scopes are usually set at 50 or 60 yards, and shotgun scopes are usually set at 60 or 75 yards.

Power:

The power of the scope is the same as magnification.

Resolution:

Resolution is the measurement of an optical device's ability to produce a sharp image by distinguishing fine detail. Resolution is determined by the quality of the glass and coatings, precision manufacturing, atmospheric conditions, and visual acuity of the user.

Reticle:

A reticle is a system of lines, dots, or crosshairs in your scope that appear superimposed on your target. There are many reticles to choose from.

Trajectory:

Trajectory is the flight of your projectile after it leaves the barrel. This flight is an arc. The amount of arc depends on the projectile weight and velocity.

Target Turret:

Finger adjustable turrets (windage and elevation adjustments) on a rifle scope. Typically they are marked with a numeric scale for quick adjustments.

Turret:

A turret is one of two knobs in the outside center part of the scope body. They are marked in increments, and are used to adjust elevation and windage for points of impact change. The elevation knob is on top and the windage knob is on the side.

Twilight Factor:

Twilight factor is the measurement of the efficiency of a rifle scope in low light conditions. The higher the twilight factor, the more useable the scope is in twilight conditions. The formula for determining twilight factor is: The square root of magnification times the diameter of the objective lens. Coatings and glass quality are not represented in this figure.

Zero:

Zero is the distance that you sighted your scope to, and references the flight of the projectile. If you are sighted in at 100 yards, you have a 100 yard zero.