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  • Airgun Terminology and Glossary

    Accessory Rail: A track for mounting hand stops or slings, installed in the fore-end of the stock.

    Accuracy: The ability of an airgun to consistently group all its shots close together at a given distance.

    Action: The "guts" of the airgun- usually the working parts of the airgun excluding the stock, barrel, barrel tube, sights. I.e. the parts that allow the gun to discharge.

    Adult airguns: Airguns intended for the discerning "Adult" market. Usually, guns classified as 'adult' are too powerful, too heavy, or too large for the typical youth and beginning shooter.

    Airgun: A gun that is powered by compressed gas to shoot a projectile (much like a spitball through a blowtube).

    AirSoft: Also referred to as 'SoftAir'. An airgun designed to shoot plastic 6mm or 8mm BBs. Airsoft guns typically shoot at lower velocities (200-250 feet per second) than BB or pellet guns, and are often replicas of real firearms but are also made of colored or clear ('see-through') plastic in areas where replica guns are banned. AirSoft guns are used in dedicated shooting competitions and 'war games' where shooters wear protective gear, primarily eye protection, and shoot at each other .

    Aperture sight: The hole (or 'aperture') with its associated frame/guide that makes up the rear sight assembly and is used to align the front sight and target.

    Back strap: The section of a pistol frame that is exposed at the rear of the gun's grip.

    Ballistic Coefficient: A measure of how a projectile decelerates during its flight through the air due to drag. The lower the BC of a projectile, the greater its air resistance.

    Barrel: The steel tube through which the projectile passes to exit the gun.

    Barrel Band: A band, usually steel (sometimes plastic on lower-quality guns and often aluminum on custom guns) placed around the forend of the guns barrel to hold it to the stock (and/or the tube assembly in PCP or Co2 guns).

    Barrel Cocking: The action of pivoting the barrel through its full range of motion (i.e. open/closed) to compress the spring in a spring-piston airgun for firing. Guns using this type of cocking are referred to as "break barrel."

    Barrel Crown: The muzzle end of a barrel where a circular, descending indentation is machined to allow the exit point for the projectile to be smooth and perpendicular to the barrel rifling. A properly-done crown helps insure accuracy and consistency in the gun's aim. A poor or uneven barrel crown often results in poor groupings, inconsistent accuracy and occasionally stray shots.

    Barrel Shroud: A metal or plastic tube that houses the gun barrel itself. Is generally used to protect smaller-bore barrels that might be damaged or bent if exposed.

    Barrel Time: The time elapsing between the projectile starting to leave its seat until exiting the muzzle. Barrel Time and Lock Time (see below) can have a significant effect on the Point Of Impact.

    BB: Popular projectile in the US; literally a steel ball (like that of a ball bearing (BB), often copper coated. In Europe, a BB is usually a lead or other soft metal round ball. Steel BB's typically weigh 5.42gr (0.35g); lead BB's weigh about 8gr (0.52g). Lead balls are slightly larger (0.17") than steel BB's (0.16"). BB's should only be used in airguns designed for them as they can/will damages rifling and loading systems on pellet-only guns.

    Bead Sight: The cylindrical top part on some front sights.

    Beavertail Forearm: A forearm or forend that is significantly wider than a typical forearm, giving it a "beavertail" type shape.

    Bedding: The fitting of the action with/to the stock.

    Benchrest: A support, for example a bipod or a stand.

    Bipod: A two-legged support attached to the fore-end of the stock.

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

    Bore: The internal circumference of a barrel to indicate its size and projectile capacity. Can be measured in Imperial units (i.e. .177"), Metric (i.e. 4.5mm). On shotguns, typically the 'gauge' system is used- i.e. a "12-gauge".

    Bottle Fed/Bottle Feed: A pre-charged pneumatic (PCP) airgun with a removeable air tank or 'bottle'. Sometimes used in reference to Co² guns using a 3oz/88g 'AirSource' bottle.

    Break Barrel: Spring-piston airgun requiring barrel cocking (see 'barrel cocking' above) to prepare the gun for discharge.

    Breaking In A Barrel: The process of initial use of a new bore by firing a number of shots and cleaning frequently. Breaking In the barrel should be done before trying to attain good Groups. Typical Break In cycles are anywhere from 100 to 1000 pellets.

    Breech: The opening to the rear chamber portion of the the barrel. In airguns this is usually the area where pellets, by whatever mean, are loaded.

    Breech Seal: The seal intended to prevent propulsion gas from leaking out behind the projectile. Usually an O-ring or leather washer. In some repeater airguns- the seal is a plastic spring-loaded shell that is attached to the valve assembly.

    Bulk Fill: Term used to describe the method of attaching a large ('bulk') Co2 source that is external to the gun- i.e. a paintball canister or "airsource" unit and its accompanying hoses/adapters.

    Bull Barrel: A barrel that is heavier than typical with very little or no taper giving it a more solid appearance and possibly better balance depending on its design.

    Butt (or butt stock): The end of the rifle that typically comes into contact with the shooter's shoulder when positioning/discharging the gun.

    Butt Plate: Protective plate made of steel, plastic, rubber or just about anything that is attached to the butt or butt stock of the gun. May also be used to cushion recoil on shoulder-mounted air rifles.

    Caliber ('cal'): The numerical value of the projectile's diameter in inches or millimeters (i.e. 0.177" or 4.5mm).

    Checkering: A diamond-like pattern for decoration or improved gripping ability. See also Stippling.

    CO2 Airgun: A gun powered by Carbon Dioxide (CO2) from a compressed liquid source. CO2 boils from a liquid state to a gas as the gun is charged. Gaseous CO2 propels the projectile when the gun is fired. CO2 typically produces pressures of 500 psi at 32F (0C) and 1000 psi at 85F (29C). Generally, an operating pressure of 850-900 psi is specified for proper airgun operation. The most commonly used CO2 dispensers used in airguns are the Crosman "Powerlet" 12 gram bulb, a 3oz (88g) one-time-use canister or 3/12/20 oz "bulk fill" tanks such as those typically used in paintball guns.

    Cocking: The action of readying a gun for discharge. Cocking may be done through a number of methods depending on the gun technology used. For example, in a break barrel gun compressing the main spring and locking the piston to the trigger pin would be 'cocking it' in preparation for shooting.

    Comb: The part of the stock where the shooter's cheek rests. Also known as a "Monte Carlo" or "cheekpiece."

    Compensator: See Muzzle Brake.

    Competition Airguns: Modern airguns designed for precision and balance used in competition/target shooting. Competition air rifles usually produce 5fpe to 6fpe (6.78J to 8.13J) muzzle energy. Pistols usually produce 3fpe to 4.2fpe (4.07J to 5.69J).

    Crown: See 'Barrel Crown'.

    Cylinder: In spring-piston airguns, the cylinder-shaped receiver or main body housing the spring, piston and other related parts.

    Deflection: The change in the path of the projectile due to passing through a medium (i.e. water- rain) or caused by wind.

    Detent: A cam or lobe, often spring-loaded, used to aid in holding a lever or barrel in a closed position.

    Diabolo: Style of pellet with a shrunked/contricted center section, or 'waist'.

    Diesel Effect/Dieseling: 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 can be destructive as its fuel-fed heat and excess recoil can damage internal gun parts and scopes attached to the gun.

    Diopter: See Open Sight.

    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.

    Drop (projectile): The measure of a projectile's drop after it crosses the line of sight for the second time; beyond the zero or sighted-in range.

    Double-Set Trigger: A trigger group made up of two separate levers/blades, the first to cock a spring-loaded mechanism that is used to assist the second, or primary, trigger blade in order to lighten the trigger pull for the shooter upon firing.

    Dovetail Rail: A slot or flaring that is tapered from one end to the other that is machined into the top surface of a barrel or action for the mounting of a scope or sight. Common sizes, or widths of a Dovetail 'rail' are 3/8", 11mm and 13mm.

    FAC: British Fire Arm Certificate. Required for any air rifle in the UK producing over 12fpe (16.27J). The majority of British and European air rifles are designed below this limit. Air pistols (any pistols) outputting more than 6fpe (8.13J) are illegal even with an FAC.

    Forearm or Forend: A mount, block, or pad placed under the barrel to be used as a rest or 'handle' when shooting.

    fpe (foot pound of energy): unit of measurement (work). Metric: Joule (J). 1 fpe = 1.3558 J. A foot pound of energy is what is required to lift one pound of weight one foot off the floor.

    fps (feet per second): Measure of speed in standard units. Metric equivalent is metres per second (mps). 1 fps = 0.3048 mps. "Fps" is also commonly referred to as a measurement of velocity. Velocity is a vector quantity, the rate of change of position in a given direction. While a projectile has velocity, all we can measure and report is speed, that is: the time taken to travel between two points.

    Gas Ram/Gas Strut: The gas strut was pioneered by Theoben in the UK and they supply them for after-market conversions of several models of UK and German HW air rifles. The strut consists of a rod and piston in a pressurised, sealed chamber. The compression and release characteristics of the gas strut are different to the traditional spring, ie. less mechanical noise during cocking and discharge and less perceived piston bounce and "recoil."

    gr (Grain): Measure of weight. 7000 gr per pound. Metric: Gram (g) 1 gr = 0.0648g.

    Gravity Feed System: A mechanism for round pellets or steel BBs to load automatically via gravity into a gun's feed/loading area.

    Grip: The handle of a handgun, or the portion of the stock immediately behind and attached to the gun's receiver on a rifle.

    Group: A cluster of holes/marks made by the same airgun/pellet combination, formed from numerous shots fired at a target using the same point of aim, for checking accuracy. Typically, 10-shot groups are used as the standard for judging a guns accuracy.

    Group Size: Measured center-to-center, the distance between the centers of the two shots placed farthest apart from one-another in a group.

    Hand Stop: A device attached to the stock's fore-end to prevent the supporting hand from sliding forward.

    Length Of Pull: The distance from the vertical center of the trigger to the vertical center of the butt plate or recoil pad.

    Loading Gate: Part of the gun that when opened allows the insertion of a projectile to be fired.

    Loading Tap: A mechanism in which projectiles are loaded and then moved to be placed into firing position. Types of taps include pop-out, turning/rotating and swinging.

    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 of inadvertently moving the gun before the projectile has actually left the barrel. Spring Piston airguns have the highest Lock Time.

    Magazine: A container or holder, either internal or external, which holds projectiles to be fed to the gun's chamber or loading area.

    Mainspring: The spring used to generate force against an airgun piston to cause gas compression (air) to force a projectile through the barrel.

    Mid Range Trajectory: In its parabola-shaped path, the highest vertical distance reached by a pellet above the line of sight.

    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.

    Monte Carlo: A style of stock with a raised comb.

    Muzzle Brake: An attachment on the end of the gun barrel to re-direct output gases (and reduce flare/flash on conventional firearms).

    Muzzle Energy: The energy of a projectile as it departs from the muzzle of a gun. Derived from the formula: 0.5 x mass x velocity squared. Units are fpe (foot pounds) or J (Joules). Muzzle energies may range from 0.5fpe (0.65J) for inexpensive pistols, to 5.5fpe (7.46J) for sporting spring pistols and competition rifles and up to 40fpe (54.23J) for the most powerful and commercially available PCP sporting rifles. The majority of sporting air rifles are 12fpe (16.27J) to 16fpe (21.69J).

    Muzzle Weight: A balancing device (often adjustable) attached at or near the muzzle end of the barrel to aid in stability in shooting and/or to equalize weight distribution while holding and aiming the gun.

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

    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: Traditional rear sight that is an open-topped V-notch or U-notch. Also known as a "peep sight" or "diopter".

    PAL: Canadian "Purchase and Acquisition License" for firearms. Firearms which can be purchases/owned in Canada only come in two classifications- "restricted" for which a PAL is required to purchase and posess, and "prohibited" for which ownership/possession is either extremely difficult or impossible. Air guns below 495fps/3.4J (4.2fpe) in output aren't classified as firearms and can be bought without a PAL, guns with outputs above this level are classified as "firearms" and require a permit. See POL (below).

    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.

    PCP (Pre-Charged-Pneumatic): The projectile is propelled by compressed air supplied from a high pressure reservoir charged from a SCUBA tank, hand pump or other external source. Operating air pressure is usually between 2000psi to 3000psi (13788kPa to 20682kPa) from a SCUBA tank charge.

    Peep Sight: See "open sight" above.

    Pellet: A lead or other soft, heavy alloy projectile.

    Picatinny Rail: A flat, serrated rail attached to a pistol or rifle for clamping a 'Weaver' style mounted scope, sight or other accessory to the gun.

    Pneumatic: The term used to describe a system using compressed air or gas as a pressure source that releases it's energy as it expands to propel a projectile through a barrel. PCP, CO², and nitrogen powered airguns work in this principle.

    Point Blank: The shooting distance to which a shooter can hit a specified target area without modifying the Point Of Aim.

    Point Of Aim (POA): The point on a target on which the sights are optically aligned.

    Point Of Impact (POI): The point where the projectile 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.

    POL: Canadian "Possession Only License"- a permit required to own (possess) a gun classified as a "firearm" (see PAL, above). A POL is only for people who owned a firearm before the Canadian Firearms Agency/Registry was created a few years ago and does not allow a person to purchase or acquire any other guns classified as firearms.

    Pre-Charged Pneumatic:See 'PCP'.

    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.

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

    Pull: Measurement of the distance from the center of the trigger's curve to the end of the buttplate. A common 'pull' for air rifles is approximately 14" on an adult-sized gun.

    Pump Airgun: Airgun powered by air compressed by a pump integral to the gun. The methods of pumping are usually either a jackknife lever used to actuate the pump rod, or a pump slide (i.e. like a conventional pump shotgun).

    Receiver: The area of the gun that ties together the different pieces such as the trigger mechanism, hammer, power assembly (piston and/or valve), and the barrel. On air pistols, the receiver is also commonly referred to as the gun's "frame".

    Recoil: The rearward thrust caused by the propulsion of the piston or the projectile. Spring piston airguns typically also have a very aggressive and powerful forward kick, caused by the piston hitting the front end of the pressure chamber.

    Recoil Pad/Butt Pad: A rubber or leather pad at the end of the butt to absorb the Recoil.

    Repeater: A gun that can fire more than one shot without having to manually reload the chamber. Rotary magazines are a common method used to achieve this.

    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: Leaning of the rifle to one side from a vertical position during firing, increasing the potential for misses, especially at longer ranges.

    Rifling: Grooves and lands forming a longitudinal twist down the barrel of a gun apply a 'spin' to the projectile to increase accuracy. Usually applied to rifles, but pellet pistols almost always have a rifled barrel. Rifle Pitch/Rate Of Twist is the distance the of the rifling required to impart a complete single revolution to a projectile.

    Rifling Pitch/Rate of Twist: The distance required in the barrel rifling that a projectile needs to spin for it to complete a single revolution.

    Scope Creep: An effect where the scope mounts creep along the Scope Rail. During the firing cycle of a spring piston powered gun, the piston bangs into the front end of the compression chamber, snapping the entire gun forward abruptly and is the main cause of scope creep.

    Scope Mounts: Devices, usually rings or clips, for mounting a scope to a rifle.

    Scope Rail: Machined grooves ('rail') to which the the scope mounts are attached.

    Side Lever Cocking: Cocking action performed by pivoting a lever (usually below the barrel) to one side to compress the main spring.

    Sight-in: Sight adjustments to get the Point Of Aim to coincide with the Point Of Impact at a preselected distance.

    Silencer/Suppressor/Moderator: A device designed to muffle the sound of the discharging of pressurized gases exiting the muzzle and help absorb sound and pressure waves.

    Skirt: The lower, or flared part below the waist of a pellet that touches the gun barrel and rifling and acts as an air seal/barrier.

    Slug: Slang for pellet or lead ball.

    SoftAir: See 'AirSoft'.

    Spring/piston gun: Airgun powered by a compressed metal spring or gas strut driving a piston, which is usually cocked in a single stroke. All guns of this type are single shot per piston release. The major disadvantage is spring "recoil" or piston jump on discharge occurring before the pellet has left the muzzle. This can upset accuracy and discourage novice shooters.

    Stippling: A random pattern of stipples for improved gripping. See Checkering.

    Stock: The removeable body of a rifle to which the mechanics of the gun are attached that is used as the handle and sometimes forearm (depending on length). See 'grip' as well.

    Swivel: A rotating loop, usually metal but sometimes plastic or other material, used to attach a carrying strap, or 'sling' to a gun.

    Terminal Velocity: The speed of the projectile upon impact with the target.

    Top-Lever Cocking: Cocking action performed by pivoting a lever at the top of the airgun upwards to compress the main spring.

    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: The connection between the pressure chamber/air reservoir and the barrel, through which the gases travel prior to propelling the pellet. Usually the port/chamber is sealed but often vents are installed to "de-tune" market- or application-specific guns.

    Trigger Pull: The force that must be applied to the trigger for it to release the sear. A good Trigger Pull is typically considered one that is light with a clean, sharp snap release.

    Tube: The cylinder-shaped tube or receiver of the gun which is used either to hold gun mechanics and/or compressed gas, depending on the power source (pneumatic or spring). See 'cylinder' as well.

    Turret: The housing for the adjustment of windage and elevation dials on scopes.

    Under-Lever Cocking: Cocking action performed by pivoting a lever below the barrel downward to compress the main spring.

    Weaver Style Mount: See 'Picatinny Rail'.

    Windage: The adjustment on the scope or sights to compensate for horizontal deflection of the projectile in flight.

    Youth Airguns: Airguns usually intended for the youth or beginner market. Such guns are characterized by lower cost, lightweight, smaller size and are easy to cock and load by someone of smaller stature.

    Zero/zero range: The range at which the Point Of Aim and the Point Of Impact are identical.

    Rifle Anatomy Picture

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