Pellet (air gun)

Apelletis a non-sphericalprojectiledesigned to be shot from anair gun,and an airgun that shoots such pellets is commonly known as apellet gun.Air gun pellets differ frombulletsandshotused infirearmsin terms of thepressuresencountered; airguns operate at pressures as low as 50 atmospheres,while firearms operate at thousands ofatmospheres.Airguns generally use a slightly undersized projectile that is designed toobturateupon shooting so as to seal the bore, and engage therifling;firearms have sufficient pressure to force a slightly oversized bullet to fit the bore in order to form a tight seal. Since pellets may be shot through asmoothborebarrel,they are often designed to be inherently stable, much like theFoster slugsused in smoothbore shotguns.

A range of "diabolo" pellets with various nose profiles

Types

Diabolo pellet

HornetCal. 4,5mm (.177). Special pellet for hunting purposes. Lead with a point of brass. Extremely high penetrating power

Hunter ImpactCal. 4,5mm (.177). Pellet for hunting purposes. Lead with a point of synthetic polymers

Thediabolo pellet(or "wasp waistpellet ") is the most common design traditionally found in airguns. It consists of a solid front portion called thehead,which can have a flat ( "wadcutter"),hemispherical( "round nose" ),hollow pointorconical( "pointed" ) front end profile, and a thin-walledfunnel-shaped hollow rear portion called theskirt,joined by anhourglass-looking narrow mid-section known as thewaist,giving the whole pellet the shape of adiabolo.The head is usually sized to just touch therifling,and this keeps the pellet centered in theborewhile keeping the friction as low as possible. The effect of friction is used in order to keep the pellet stationary until the piston has reached the end of its travel, compressing as much air as is possible.The thin hollow skirt is made of a malleable material, usuallylead,although non-toxic alternatives are available that usetinor even plastic. During shooting, the skirt flares out andobturatesthe bore when pressure builds up behind it to provide a goodsealthat allows efficient pellet acceleration, and engages the rifling whereby imparting spin. In asmoothborebarrel, the skirt will still flare to provide a tight seal, but since there is no rifling the pellet will not spin, and is less accurate.

Because the majority of the pellet's mass resides in the solid head in the front, and the hollow skirt in the back generates significantdragduring flight, this createsdrag stabilitythat will counteractyawingand help to maintain consistent trajectories. However, such stability is limited, and if the pellet's speed exceeds what the aerodynamics allow it will become unstable and start tumbling in flight. When this happens, the pellet can hit the target sideways and leave behind akeyhole-shaped impact hole on the target paper, instead of a clean round hole as expected from a direct frontal hit. This phenomenon is known askeyholing.

Pellets are designed to travel atsubsonicspeeds. High velocities can cause light pellets to overly deform, or even break apart in flight. Thetransitionfrom subsonic to supersonic velocities will cause almost all pellets to tumble. The closer a pellet gets to thespeed of sound,the more unstable it becomes. This is a problem for high-powered "magnum" break-barrel and pre-charged pneumatic air rifles, which are capable of pushing lighter pellets beyond thesound barrier.A few companieshave addressed this issue by manufacturing heavier-than-normal pellets for use in these high powered air guns.The heavier weight of these pellets ensures lowermuzzle velocities,resulting in less chance of tumbling and more overall accuracy. Their weight also makes themsectionally denserand less susceptible towind deviationand drag deceleration, and thus imparts betterexternalandterminal ballisticperformance.

Ball pellets

Steel ball shots withcopperorzincjackets

Main article:BB gun

The earliest airgun pellets are actually small roundlead shotssimilar to those used inmuskets.First popularized by theDaisyBB Gun in the 1890s, a spring-piston airgun that shot "BB" -sizebirdshots,the.180-caliber lead shots were later replaced by the lighter.175-caliber steel shots modified frombearing balls,and remained popular as aplinking/pest shootingprojectile due to the popularity and affordability ofBB gunssuch as theDaisy Red Ryder.

Modern BB guns use the same calibers as the pellet guns, namely the.177 caliber and (occasionally).22 caliber.Galvinized/copper-coatedsteel balls are the commonest projectile used in BB guns due to their bettermuzzle speedandpenetration,but are only used insmoothborebarrelsdue to the risk ofwearingdownriflings,therefore lead balls are still used for rifled barrels.

Slug pellet

EisenherzCal. 4,5mm (.177). Plastic-coated pellet with a core of hard metal. For hunting purposes.

Plastic-coated pellets with a pointed steel core: Highest possible penetration power. Top: For rifles, bottom: for CO2-pistols with a revolver magazine

Recently, some manufacturers also have introduced the morecylindro-conoidallyshaped "slug"pellets for some of the more powerful modern PCP air rifles. Contrasted to the commonly used diabolo pellets, these slug pellets resembleMinié balls,withcanneluresand ahollow base,and have more contact surface with the bore and hence need greater propelling force to overcome friction, but they have betterballistic coefficientsand thus longer effective ranges due to the more aerodynamic shape. Because these slug pellets have no skirts to generate enough drag stability in flight, they rely on spin stabilization from a fully rifled barrel.

Lead-free pellets

There are many different kinds of lead-free pellets, utilizing non-lead alloys and/or plastics in their construction. Consequently, they are much lighter than lead pellets, with weights ranging from 5.1 to around 20 grains. Due to their lighter weight, they accelerate more quickly inside the barrel, and commonly reach supersonic velocities. This increases the effectivefeet per second(FPS) of an airgun, which can result in greater accuracy.

However, lead-free pellets typically have a lowerballistic coefficient(BC), which results in more wind-drift, and reduced velocity at longer distances. As an example, H&N Sport's Baracuda Green pellet has a BC of 0.013, but the standard Baracuda pellet's BC is 0.024.

Although some airguns are equipped with moderators or other noise dampening chambers, lead-free pellets can break the sound-barrier, and produce a loud cracking noise. This can be misinterpreted as a malfunction of the suppressor, when in fact it results from using a supersonic pellet. Upon switching back to a lead pellet, the supersonic crack will cease.

H&N Sport markets their lead-free pellets as part of their "GreenLine," and Gamo markets their lead-free pellets as a "Performance Ballistic Alloy" (PBA). Regardless of the terminology, the underlying technology involves a mix of non-lead materials, such as zinc, iron, tin, or copper. Lead-free pellets are offered by all major manufacturers, including RWS, Gamo, H&N Sport, Predator International, JSB, Crosman, SIG Sauer, and others.

These metals are all lighter than lead, and significantly harder. As a result, they penetrate more deeply, and do not deform as greatly upon impact with the target. By contrast, lead pellets are often designed to fragment, expand, or mushroom, and can cause more damage. As a result, they are favored by hunters. However, many hunters are using non-lead pellets, to avoid lead contamination.

Match shooting use

A H&N Final Match Pistol 4.5 mm (.177 in) match diabolo pellet

Match pellets are used for the10 metre air rifleand10 metre air pistoldisciplines. These 4.5 mm (0.177 in) calibre pellets havewadcutterheads, meaning the front is (nearly) flat, that leave clean,hole punch-like round holes in paper targets for easy scoring. Match pellets are offered in tins and more elaborate packagings that avoid deformation and other damage that could impair their uniformity.

Most match pellets are made of soft lead (aleadalloy with lowantimonycontent), but some companies offer lead-free versions. The antimony content is used to control the hardness of the soft lead alloy. It is a very soft alloy, which makes it easy to process. Since the soft lead alloy is prone to strongly deform when striking a bullet catcher, it rapidly loses its kinetic energy and will not easily bounce off. Lead is toxic and hazardous to the environment, so precautions should be taken if shooting with lead pellets. For this reason, many shooters use lead-free match pellets, produced by H&N Sport, Predator International, JSB, RWS, Olympia Shot, Gamo, or Daisy.

Match air gun shooters are encouraged to perform shooting group tests with their gun clamped in a fixed rest in order to establish which particular pellet type performs best for their air gun. To facilitate maximum performance out of various air guns the leading match pellet manufacturers produce pellets in graduated weight variants (the light/high speed variants are often marketed for air pistol use) and with graduated "head sizes", which means the pellets are offered with front diameters from 4.48 mm (0.176 in) up to 4.52 mm (0.178 in).

However at higher and top competitive levels, even these variations are thought too coarse-grained and match pellets arebatch tested;that is, the specific gun is mounted in a machine rest test rig and pellets from a specific production run on a specific machine with the same ingredients fed into the process (abatch) are test-fired through the gun.Many different batches will be tested in this manner, and the pellets which give the smallestconsistentgroup size without fliers (shots which fall outside of the main group) will be selected (small but inconsistent group sizes are not useful to a top competitor); and the shooter will then purchase several tens of thousands of pellets from that batch. Group sizes of 4.5 mm (0.177 in) diameter are theoretically possible, but practically shot groups of 5.0 mm (0.197 in) are considered highly competitive.Unbatched ammunition, especially if the air gun is not regularly cleaned, is generally thought to be capable of only 8.0 mm (0.315 in) diameter group sizes. Batch testing match pellets for a particular gun is not generally thought to be worthwhile until the shooter reaches a high proficiency level, around the 95% level (570 for men, 380 for women).

See also

• Air gun
• Airsoft pellet
• BB gun

External links

Media related toAir gun pelletsat Wikimedia Commons