Airgun technical terms
PUBLISHED: 16:19 27 October 2011 | UPDATED: 16:23 27 October 2011
Your guide to the technical terms associated with airgunning...
ACTION: This is a general description for the working parts of any airgun. In spring-powered airguns it will mean the cylinder, within which the spring, piston, seal, cocking linkage and other parts are linked to the trigger.
ADJUSTABLE TRIGGER: A trigger mechanism that can have its weight of pull and/or other features adjusted to suit the shooter.
AIR TANKS, GAUGES AND HOSES: These are accessories required for filling up pre-charged airguns - which use ultra-clean and dry divers quality compressed air from diving bottles. The hoses link the air bottle to the airguns cylinder and the gauge measures and meters the precise amount needed to fill the airguns air store known as the reservoir.
BARREL WEIGHT: This is a weight on the end of a rifle barrel (usually a spring gun) that looks like a silencer, but is actually to improve the overall performance of the rifle.
BORE: The inner part of a barrel down which the pellet passes when the gun is fired. The bore of a barrel is usually rifled, having helical grooves cut along its length, although it can be a smooth-walled. Rifled barrels are inherently more accurate as the grooves are designed to spin the pellet as it is pushed through the bore by the compressed air behind it. This adds stability by way of its gyroscopic effect.
BREECH: Opening where the pellet is placed in the barrel.
BREECH SEAL: The rubber ring that goes round the breech to provide an air tight seal with the transfer port.
BI-POD: Twin-legged rifle support which can be fixed to a rifles barrel but more usually mounted underneath the foreend. Most types can fold away while the gun is being carried different designs fold forward or back and the legs are telescopic and adjustable to suit the angle of the shot.
C-C@25: This means centre to centre at 25 yards and defines the impact points of a group of pellets, measured from the centre of the extreme left-hand pellet hole to the centre of the far righthand hole, at a given distance in this case, 25 yards or metres.
CASE MAT: A rifle case that opens up into a mat that can be used by the shooter to lie on when shooting from the prone position. These are popular in FT and HFT and are becoming more so in hunting.
CHEQUERING OR CHECKERING: The finely cut parallel lines, crosshatched to form diamond shapes incised into the woodwork of a gunstock to improve grip and aid safe gun-handling. Can be hand or machine-cut, most modern and precise examples being laser-cut to very fine tolerances.
CO2: These are rifles and pistols powered by small CO2 cylinders, rather like the ones you find in a soda siphon. You can get semiautomatic pistols powered by CO2 and they are great fun. The rifles are multi-shot and are usually bolt-action. The rifles are powerful enough to hunt small vermin, but CO2 airguns can lose power in cold weather. The gas refills can also be quite expensive.
DIABOLO: The term which describes the shuttlecock shape of a standard airgun pellet. The waisted design creates two distinct areas; the head which can be variously shaped to suit different purposes, and the skirt which has thin walls and is forced by the air pressure behind it to conform to the grooves of the rifling. This not only creates a perfect seal but it also allows the rifling grooves to provide maximum effect on stability and accuracy.
FAC: These letters are used as an abbreviation of Firearms Certificate, a licence granted by the police in order to own and use any air rifle capable of producing over 12ft.lbs. of muzzle energy. The absolute power limit for pistols is 6ft.lbs. and may not be legally exceeded.
FIRING VALVE: As youd expect, this is a valve but one that is specific to precharged pneumatic airguns (PCP). When the trigger of a PCP airgun is released, an internal hammer strikes the valve to force it open and release the measured quantity of air needed for each shot.
FORE-END: An air rifles stock can be made from wood most usually beech or walnut though laminates, plastic and even metal can also be used. The part of a rifles stock from in front of the trigger to the point at which it ends, beneath the barrel or air reservoir, is the fore-end.
FPS: An abbreviated form of feet per second, which is a unit of velocity. It expresses the distance in feet traveled, divided by the time in seconds. It is used to measure muzzle velocity (see below).
FT: Short for field target. The sport started in the early 1980s and competitors are required to hit specific kill zones on various metal knock-down targets that are spread out over a specially designed course. It tests the shooters skill at shooting at various ranges and in different positions. A typical course will have 30-50 targets with one shot allowed for each target.
FT.LBS: The term used to describe and measure the power of an airgun. The technical definition is the amount of energy or work needed to raise an item weighing one pound the distance of a foot. The legal limit for air rifles in the UK is 12ft.lbs and for air pistols it is 6ft.lbs.
HEAD: Most airgun pellets are a diabolo shape, best described as being waisted with the top section being the head and the lower the skirt. The head is the frontal area which can be domed, flattened, pointed or cup-shaped.
HOCKING: This is where you make an incision in a dead rabbits back leg between the tendon and the bone, then thread the other leg through that hole so the legs are joined together. This makes carrying large quantities of rabbits easier because you can thread their legs through a pole and carry them on that, or hang them on a fence or twig and collect them later.
HOLDOVER/UNDER: Is a method of applying range correction to allow for the curved flight of the pellet. You hold over when you aim high to compensate for pellet drop in trajectory at a long range and hold under is when the shooter aims under the target to compensate for the closer range targets.
HFT: Is short for hunter field target. Pete Sparkes was one of its originators and the sport is a less formal version of field target (see above) where competitors go round a specially designed course and shoot as many knockover targets as they can. It tests the shooters ability to shoot from all sorts of positions and in all sorts of weather conditions. United Kingdom Association of Hunter Field Target (UKAHFT) has become a dominant force within the sport and with national events attracting more than 200 shooters.
INLET FILTER: Tiny, very fine filter situated at the point where a charging hose connects to the air reservoir of a PCP airgun. Its job is to trap any particles of dirt or grit that might get into the action of the gun and which could, potentially, cause severe damage.
JOULE: A metric unit of energy used to measure the power of an airgun. A legal limit air rifle in the UK will be being around 16 joule (12ft.lbs).
LENGTH OF PULL: The length from the trigger to the rear force of the recoil pad. The average length of pull is 13 inches, which suits the arm length of 80% of the population.
M.E.: Stands for muzzle energy and is another means of describing an airguns power. The energy measured is that of the pellet and relates to speed at which it leaves the muzzle combined with its weight and processed via a mathmatical equation.
MODERATOR: Posh name for a silencer, which helps reduce muzzle crack when the pellet leaves the barrel of the rifle.
MUZZLE: The end of an airguns barrel and the point at which the pellet leaves the confines of the bore and the directional influence of the rifling. The actual rim of the muzzle is known as the crown and is the final point at which the pellet is controlled by the barrel. Although measured in microns, the way in which this crown is finished can have a dramatic effect on the pellets velocity and accuracy.
ON TICKET: See Firearms Certificate.
P.A.SCOPE: Short for 'parallax adjustable and describes the scopes ability to be focused on its target. It is essential to get the reticle and the target in focus at the same time to aid accuracy. This is achieved on a scope that is adjustable for focus by moving a side wheel on the left of the scope, or by rotating a moveable objective bell to bring both images the reticle and the target - into focus at the same time.
PARALLAX ERROR: This is the error in the apparent point of aim against the actual point of aim, usually due to misalignment of the shooters eye and the scopes axis. Sometime the shooters eye drifts off centre, an apparent shift will occur between the relative positions of the reticle and the target images. The shooter is now likely to move the airgun to place the image of the reticle where he first established it on the target. This results in what is known as parallax error and the shot will hit the target slightly away from where the shooter expects it to land. This can be overcome with a scope that is adjustable for focus and a rifle that fits correctly.
PAUNCHING: This just means gutting a dead rabbit.
PCP: Is an acronym for pre-charged pneumatic. This is a rifle or pistol powered by compressed air and is a popular power source for hunters because many of these rifles are multi-shot. Its also popular with target shooters in single-shot format because there is very little recoil with this power source, which aids accuracy. The downside is that it can be more expensive to use a PCP because you have to buy a divers tank or high pressure stirrup pump to re-charge the rifles air reservoir.
PISTON: Cocking a spring-powered airgun pushes back its internal piston and compresses the spring within the compression tube. When the trigger is released, the piston is driven forward by the mainspring which uncoils to compresses the air in front of it, forcing the pellet into the barrel and on its way down the bore.
POWERPLANT: Another name for the energy producing parts of an airgun, most commonly used to describe the mainspring, piston and compression tube.
PROFILE STOCK: Also known as a skeleton stock. This is where parts of the stock have been cut out to make it lighter.
RECOIL ARRESTOR: Spring guns have a lot of recoil and this can cause scopes to move back on the scope rails. A recoil arrestor is a metal stud or band that prevents the scope from sliding back.
REGULATOR: Device fitted to higher quality pre-charged pneumatic airguns. It is designed to feed precisely metered amounts of air from the reservoir to the breech area in order to power each shot consistently. Capable of adding significantly to efficiency but also to cost.
RETICLE: This is the name for an aiming reference on a telescopic sight that usually takes the form of cross hairs, often with aiming marks on it.
RIM FIRE: This is where the primer is on the rim of the cartridge case and is now largely used on older rifles or lower powered .22 calibre rifles.
SCHNABEL TIP: This is where the forestock finishes with a downward curl and provides a natural hand hold or stop. There are different theories as to how this end to the forestock got its name. Some say it is named after the German for beak, others say it was invented by a man called Schnabel.
SINGLE-STAGE TRIGGER: On a rifle with a single-stage trigger, the first movement of the trigger fires the rifle.
SKIRT: The flared lower section of an airgun pellet. Thin walled to allow air pressure behind it to force the soft leadalloy from which it is made into the rifling and make an effective seal.
SLEEVED BARREL: A barrel that sits inside a tube, or sleeve. Can be simply to add chunkiness in a bullbarrel style, to add strength, or best of all to house an integral silencer without changing the overall outline of the barrel.
THUMBING A RABBIT: To get rid of the urine in a dead rabbits bladder, you can run your thumb down the rabbits belly to squeeze any urine out of it. This is done because the urine can taint the meat.
TRANSFER PORT: The port directly opposite the breech that the air comes through from the power plant to force the pellet down the barrel before.
TWO-STAGE TRIGGER: A trigger mechanism that has two definite stages; a take-up stage, and a release stage. On a lot of two-stage triggers, the first stage is just the resistance offered by the trigger return spring, but on more expensive target airguns, some of the triggers total pull weight is loaded onto the first stage as well to make a smoother release. The benefit of a two-stage trigger over a single-stage trigger is that the shooter can take up the first stage, hold, then follow-through with the shot when the sight picture looks right.
TUNING: Process of getting the best mechanical performance from an airgun. Can vary between simply re-polishing and lubricating the moving parts inside, to a full systems upgrade which results in smoother and significantly improved performance.
TURRETS: On a rifle scope the turrets house the adjustors for the scopes windage, and elevation.
VERMIN: General term more commonly defined as pest species rather than the outmoded word vermin used to describe animals and birds which may be controlled by shooting by Authorised Persons with permission to act on behalf of the landowner. Chiefly the word is used to describe the following: carrion crow, hooded crow (Scotland), magpie, rook, jackdaw, jay, woodpigeon, feral pigeon, collared dove, rat, rabbit and grey squirrel. Other species listed within the Wildlife and Countryside Act as pests include greater and lesser black-backed gulls and others.
WEIGHT OF PULL: This refers to the amount of effort needed to pull the trigger to the release point. It is usually measured in pounds and on many airguns the weight of pull can be adjusted to suit the shooter.
WHITE LINE SPACERS: These are pieces of white plastic or wood often placed between the butt and the recoil pad. They are largely cosmetic.
ZOOM: Adjustable magnification facility of a telescopic sight. Magnification of a 3-9 x scope, for instance, can be varied between 3 and 9 times larger than seen through the naked eye.