Air gun / Air rifle
An Air Gun / Air Rifle (also called pellet
gun) is any variety of projectile weapons that propels projectiles by
means of compressed air or other gas, in contrast to firearms, which use
a propellant charge. Both the rifle and pistol forms (air rifle and air
pistol) typically propel metallic projectiles, either pellets, or BBs.
Certain types of air guns, usually rifles, may also propel arrows.
Airsoft guns propel plastic projectiles.
History Of Air gun / Air rifle
Air
guns represent the oldest pneumatic technology. The oldest existing
mechanical air gun, a bellows Air Gun / Air Rifle dating back to about
1580, is in the Livrustkammaren Museum in Stockholm. This is the time
most historians recognize as the beginning of the modern air gun.
In
the 17th century, air guns, in calibers .30–.51, were used to hunt big
game deer and wild boar. These air rifles were charged using a pump to
fill an air reservoir and gave velocities from 650 to 1,000 feet per
second (200–300 m/s). They were also used in warfare; the most
recognized example being the Girandoni Military Repeating Air Rifle.
At
that time, they had compelling advantages over the primitive firearms
of the day. For example, air guns could be fired in wet weather and rain
(unlike matchlock muskets), and fired with greater rapidity than
muzzle-loading guns.[1] Moreover, they were quieter than a firearm of
similar caliber, had no muzzle flash, and were smokeless. Thus, they did
not disclose the shooter's position or obscure the shooter's view,
unlike the Black powder muskets of the 18th and 19th centuries.
In
the hands of skilled soldiers, they gave the military a distinct
advantage. France, Austria and other nations had special sniper
detachments using air rifles. The Austrian 1770 model was named
Windbüchse (literally "wind rifle" in German). The gun was developed in
1768 or 1769[2] by the Tyrolean watchmaker, mechanic and gunsmith
Bartholomäus Girandoni (1744–1799) and is sometimes referred to as the
Girandoni Air Rifle or Girandoni Air Gun / Air Rifle in literature (the
name is also spelled "Girandony," "Giradoni"[3] or "Girardoni".[4]) The
Windbüchse was about 4 ft (1.2 m) long and weighed 10 pounds (4.5 kg),
about the same size and mass as a conventional musket. The air reservoir
was a removable, club-shaped, butt. The Windbüchse carried twenty-two
.51 caliber (13 mm) lead balls in a tubular magazine. A skilled shooter
could fire off one magazine in about thirty seconds. A shot from this
Air Gun / Air Rifle could penetrate an inch thick wooden board at a
hundred paces, an effect roughly equal to that of a modern 9 mm or .45
ACP caliber pistol.
Kunitomo Air Gun / Air Rifle developed by the Japanese inventor Kunitomo Ikkansai, circa 1820–1830
Kunitomo Air Gun / Air Rifle trigger mechanism
Circa
1820, the Japanese inventor Kunitomo Ikkansai developed various
manufacturing methods for guns, and also created an Air Gun / Air Rifle
based on the study of Western knowledge ("rangaku") acquired from the
Dutch in Dejima.
The celebrated Lewis and Clark Expedition (1804)
carried a reservoir air gun. It held 22 .46 caliber round balls in a
tubular magazine mounted on the side of the barrel. The butt served as
the air reservoir and had a working pressure of 800 psi (5,500 kPa). The
rifle was said to be capable of 22 aimed shots per minute and had a
rifled bore of 0.452 in (11.5 mm) and a groove diameter 0.462 in (11.7
mm).
One of the first commercially successful and mass-produced
air guns was manufactured by the W.F. Markham Co. Their first model Air
Gun / Air Rifle was called the Challenger and marketed in 1888. Their
next model was the Chicago followed by the King. The Chicago model was
sold by Sears, Roebuck for 73 cents in its catalog. In 1928 the name of
the company was changed to King Mfg. Co. and remained so until the
company was purchased by the Daisy Air Gun / Air Rifle company.[5]
During
the 1890s, air rifles were used in Birmingham, England, for competitive
target shooting. Matches were held in public houses, which sponsored
shooting teams. Prizes, such as a leg of mutton for the winning team,
were paid for by the losing team. The sport became so popular that in
1899, the National Smallbore Rifle Association was created. During this
time over 4,000 air rifle clubs and associations existed across Great
Britain, many of them in Birmingham. During this time, the Air Gun / Air
Rifle was associated with poaching because it could deliver a shot
without a significant report.
Advantages of Air gun / Air rifle
The
most basic difference between an Air Gun / Air Rifle and traditional
gun is that the latter requires gun powder. Air guns are comparatively
safer to use since while using them there is no risk of gun powder burns
on the hands and face.
Another major advantage is that the air
rifles are less noisy and easy on the ears of users. The most important
advantage, however, is that they can be used conveniently for both
hunting as well as sporting activities. Air rifles also have an
advantage over conventional rifles when it comes to pricing—air rifles
are a lot cheaper. In addition, unlike conventional rifles, air rifles
can have a variety of uses.
Use
Air guns are used for hunting,
pest control, recreational shooting (commonly known as plinking), and
competitive sports, such as the Olympic 10 m Air Rifle and 10 m Air
Pistol events. Field Target (FT) is a competitive form of target
shooting in which the targets are knock-down metal silhouettes of
animals, with a 'kill zone' cut out of the steel plate. Hunter Field
Target (HFT) is a variation, using identical equipment, but with
differing rules. The distances FT and HFT competitions are shot at range
between 7.3 and 41.1 metres (24 and 135 ft) for HFT & 7.3 and 50.29
metres (24.0 and 165.0 ft)for FT, with varying sizes of 'reducers'
being used to increase or decrease the size of the kill zone. In the UK,
competition power limits are set at the legal maximum for an unlicensed
air rifle, i.e. 12 ft·lbf (16 J).
Legal issues / Law Of Air gun / Air rifle
While
in some countries air guns are not subject to any specific regulation,
in most there are laws, which differ widely. Each jurisdiction has its
own definition of an air gun; and regulations may vary for weapons of
different bore, muzzle energy or velocity, or material of ammunition,
with guns designed to fire metal pellets often more tightly controlled
than airsoft weapons. There may be minimum ages for possession, and
sales of both air guns and ammunition may be restricted. Some areas
require permits and background checks similar to those required for
firearms proper.
Air Gun / Air Rifle power sources
The
different methods of powering an Air Gun / Air Rifle can be broadly
divided into 3 groups: spring-piston, pneumatic, and CO2. These methods
are used in both air rifles and air pistols.[6]
Spring-piston
A typical break-barrel cocking spring-powered air rifle
Spring-piston
air guns are able to achieve muzzle velocities near or greater than the
speed of sound from a single stroke of a cocking lever or the barrel
itself. The effort required for the cocking stroke is usually related to
the power of the gun, with higher muzzle velocities requiring greater
effort.
Spring-piston guns operate by means of a coiled steel
spring-loaded piston contained within a compression chamber, and
separate from the barrel. Cocking the gun causes the piston assembly to
compress the spring until the rear of the piston engages the sear. The
act of pulling the trigger releases the sear and allows the spring to
decompress, pushing the piston forward, thereby compressing the air in
the chamber directly behind the pellet. Once the air pressure has risen
enough to overcome any static friction and/or barrel restriction holding
the pellet, the pellet moves forward, propelled by an expanding column
of air. All this takes place in a fraction of a second, during which the
air undergoes adiabatic heating to several hundred degrees and then
cools as the air expands.
Spring-piston guns have a practical
upper limit of 1250 ft/s (380 m/s) for .177 cal (4.5 mm) pellets. Higher
velocities cause unstable pellet flight and loss of accuracy. This is
due to the extreme buffeting caused when the pellet reaches and passes
transonic speed, then slows back down and goes through it again. This is
more than enough to destabilize it. Shortly after leaving the barrel,
the supersonic pellet falls back below the speed of sound and the shock
wave overtakes the pellet, causing its flight to be disrupted. Drag
increases rapidly as pellets are pushed past the speed of sound, so it
is generally better to increase pellet weight to keep velocities
subsonic in high-powered guns. Sonic crack from the pellet as it moves
with supersonic speed also makes the shot louder sometimes making it
possible to be mistaken for firearm discharge. Many shooters have found
that velocities in the 800–900 ft/s (240–270 m/s) range offer an ideal
balance between power and pellet stability.
Most spring piston
guns are single-shot breech-loaders by nature, but multiple-shot guns
have become more common in recent years. Spring guns are typically
cocked by a mechanism requiring the gun to be hinged at the midpoint
(called a break barrel), with the barrel serving as a cocking lever.
Other systems that are used include side levers, under-barrel levers,
and motorized cocking, powered by a rechargeable battery.
Spring
piston guns, especially high-powered ones, recoil as a result of the
forward motion of the piston. Although the recoil is less than that of
some cartridge firearms, it can make the gun difficult to shoot
accurately as the recoil forces are in effect whilst the pellet is still
traveling down the barrel. Spring gun recoil has a sharp forward
movement too, caused by the piston hitting the forward end of the
chamber when the spring has fully expanded. These two reactions are
known to damage telescopic sights not rated for spring gun use.
Spring
guns can also suffer from spring vibrations that reduce accuracy. These
vibrations can be controlled by adding features like close-fitting
spring guides or by aftermarket tuning done by "air-gunsmiths" who
specialize in Air Gun / Air Rifle modifications. A common modification
is the addition of viscous silicone grease to the spring, which both
lubricates it and dampens vibration.
The better quality spring
air guns can have very long service lives, being simple to maintain and
repair. Because they deliver the same energy on each shot, their
trajectory is consistent. Most Olympic Air Gun / Air Rifle matches
through the 1970s and into the 1980s were shot with spring-piston guns,
often of the opposing-piston recoil-eliminating type. Beginning in the
1980s, guns powered by compressed, liquefied carbon dioxide began to
dominate competition. Today, the guns used at the highest levels of
competition are powered by compressed air.
Gas Spring
Some
makes of air rifle incorporate a gas spring instead of a mechanical
spring. Pressurized air or nitrogen is held in a chamber built into the
piston, and this air is further pressurized when the gun is cocked. It
is, in effect, a gas spring commonly referred to as a "gas ram" or "gas
strut". Gas spring units require higher precision to build, since they
require a low friction sliding seal that can withstand the high
pressures when cocked. The advantages of the gas spring include the
facility to keep the rifle cocked and ready to fire for long periods of
time without long-term spring fatigue, lower recoil and faster "lock
time" (the time between pulling the trigger and the pellet being
discharged). The improvement in lock time results in better accuracy.
Pneumatic
Pneumatic
air guns utilize compressed air as the source of energy to propel the
projectile. Single-stroke and multi-stroke guns utilize an on board pump
to pressurize the air in a reservoir. Pre-charged pneumatic guns'
reservoirs are filled using either a high-pressure hand pump or by
decanting air from a diving cylinder. This design, having no significant
movement of heavy mechanical parts during the firing cycle, produces
lower recoil.
Multi-stroke
Multi-stroke pneumatic air guns
require the pumping of an on-board lever to store compressed air within
the air gun. Variable power can be achieved through this process, as the
user can adapt the power level for long, or short-range shooting.
Single-stroke
The Walther LGR single-stroke pneumatic match air rifle
A
single motion of the cocking lever is all that is required to compress
the air. The single-pump system is usually found in target rifles and
pistols, where the higher muzzle energy of a multi-stroke pumping system
is not required. Single-stroke pneumatic rifles dominated the national
and international ISSF 10 metre air rifle shooting events from the 1970s
up to the 1990s.
Pre-charged pneumatic (PCP)
An example of a Benelli Kite pre-charged pneumatic air pistol, as used in 10 metre air pistol ISSF shooting events
Pre-charged
pneumatic (PCP) air guns are usually filled by decanting from an air
reservoir, such as a diving cylinder or by charging directly with a hand
pump. Because of the need for cylinders or charging systems, PCP guns
have higher initial costs but much lower operating costs when compared
to CO2 guns. PCP guns have very low recoil and can fire as many as 500
shots per charge. The ready supply of air has allowed the development of
semi and fully automatic[7][8] air guns. PCP guns are very popular in
the UK and Europe because of their accuracy and ease of use. They are
widely utilized in ISSF 10 metre air pistol and rifle shooting events,
the sport of Field Target shooting,[9] and are usually fitted with
telescopic sights.
Early hand pump designs encountered problems
of fatigue (both human and mechanical), temperature warping, and
condensation. None of which are beneficial to accurate shooting or Air
Gun / Air Rifle longevity. Modern hand pumps have built-in air
filtration systems and have overcome many of these problems. Using
scuba-quality air decanted from a scuba cylinder provides consistently
clean, dry, high-pressure air.
Unregulated action
During
the typical PCP's discharge cycle, the hammer of the rifle is released
by the sear to strike the bash valve. The hammer may move rearwards or
forwards, unlike firearms where the hammer almost always moves forward.
The valve is held closed by a spring and the pressure of the air in the
reservoir. The pressure of the spring is constant, and the pressure of
the air decreases with each successive shot. As a result, when the
reservoir pressure is at its peak, the valve opens less fully and closes
faster than when the reservoir pressure is lower, resulting in a
similar total volume of air flowing past the valve with each shot. This
results in a degree of self-regulation that gives a greater consistency
of velocity from shot to shot. A well-designed PCP will display good
shot to shot consistency as the air reservoir is depleted.
Regulated action
Other
PCP rifles and pistols are regulated, i.e. the firing valve operates
within a secondary chamber separated from the main air reservoir by the
regulator body. The regulator maintains the pressure within this
secondary chamber at a set pressure (lower than the main reservoir's)
until the main reservoir's pressure drops to the point where it can no
longer do so. As a result, shot to shot consistency is maintained for
longer than in an unregulated rifle.
CO2
CO2 pistol and disposable cylinders
Most
CO2 guns use a disposable cylinder, a powerlet, that is purchased often
pre-filled with 12 grams of pressurized carbon dioxide, although some,
usually more expensive models, use larger refillable CO2 reservoirs like
those typically used with paintball markers.
Carbon dioxide-powered guns have two significant advantages over pre-charged pneumatic air guns:
A simpler system for compact storage of energy—a small volume of liquid converts to a large volume of pressurized gas.
No pressure regulator. Within a temperature range tolerable to humans
there is little need to regulate the inherently suitable pressure for
low-to-moderate-power air guns. The vapor pressure is dependent only on
temperature, not tank size, as long as some liquid CO2 remains in the
reservoir. So, as long as the CO2 cylinder is not allowed to cool
significantly (through firing), the pressure will not decrease by a
significant degree. However, at higher temperatures (e.g. on a hot
summer day), this approximation does not hold true.
These two
advantages allow CO2 guns to be constructed more simply than guns using a
pressurized air reservoir. Some CO2-powered guns have detachable or
fixed reservoirs that are loaded with pressurized gas from a larger
cylinder. Most CO2 powered guns use the standard 12 gram Powerlet
disposable cylinder standardized by Crosman.
CO2 guns, like
compressed air guns, offer power for repeated shots in a compact package
without the need for complex cocking or filling mechanisms. The ability
to store power for repeated shots also means that repeating arms are
possible. There are many replica revolvers and semi-automatic pistols on
the market that use CO2 power. These guns are popular for training, as
the guns and ammunition are inexpensive, safe to use, and no specialized
facilities are needed for safety. In addition, they can be purchased
and owned in areas where firearms possession is either strictly
controlled, or banned outright. Most CO2 powered guns are relatively
inexpensive, although there are still a few precision target guns on the
market that use CO2. The CO2 system has been used in experimental
non-lethal law enforcement weapons, where high power delivery systems
launch rubber batons or bean bags out of a gas-powered launcher, much
like a non-lethal shotgun system (but at lower velocities, thus being
safer).
Safety
For safety, CO2 containers must be kept at
temperatures below 120 °F (49 °C) ; at temperatures above this level,
the pressure begins to increase very rapidly, and can cause the
container to fail. CO2 containers with diameters at or above two inches
(50 mm) have a pressure release "rupture" mechanism to release the
contents over a certain pressure level and avoid explosion because of
high temperature. These disks are generally calibrated to a minimum
pressure corresponding to the 120 °F (49 °C) level at 100% of the rated
CO2 capacity. Elevated temperatures, even those below the critical
temperature, can cause increased leaking through seals.
Operating considerations
Re-filling Forcing more carbon dioxide gas into a reservoir of liquid
and gas CO2 while maintaining a constant temperature would not raise the
pressure but merely convert the additional gas into liquid. By chilling
the vessel to be filled, the lower vapor pressure will pull CO2 from
the source container. While the pressure in the reservoir is generally
dependent only on the temperature, if the bottle is too full, that
changes. The expansion of the liquid CO2 will take up all the space in
the bottle, preventing evaporation. At this point, the pressure increase
with temperature becomes dangerously high. Cooling Each time
the gun is fired there is rapid evaporation of liquid to gas, which is
an endothermic process in which the pressure drops until enough ambient
heat is absorbed to restore the pressure. When shooting at a rate faster
than the cylinder can absorb heat from the environment to counter the
cooling of the evaporating liquid, the pressure will drop, and the
velocity is likely to drop as well in a non-regulated gun.
Ammunition
A .177 (4.5mm) caliber "Wadcutter" pellet next to a stick of chewing gum
Pellet
.177 caliber pellet exiting an air pistol, photographed with a high speed air-gap flash
The
most popular ammunition used in rifled air guns is the lead diabolo
pellet. This waisted projectile is hollowed at the base and available in
a variety of head styles. The diabolo pellet is designed to be drag
stabilized, though is not as stable as some other shapes in the
transonic region (272–408 m/s ~ 893–1340 ft/s). Pellets are also
manufactured from tin, or a combination of materials such as
steel-tipped plastic.
Most air guns are .177 (4.5 mm) or .22 (5.5
mm / 5.6 mm), and are designed for target practice, small game hunting
and field target shooting. Cost per round is less than $0.02 (US) for
Olympic-quality ammunition, and far less for cheaper grades. Though less
common, .20 and .25 caliber (5.0 mm and 6.4 mm) guns also exist and are
used predominantly for hunting.
BB
Steel BBs coated with copper and nickel
The
BB was once the most common Air Gun / Air Rifle ammunition in the USA. A
BB is a small ball, typically made of steel with a copper or zinc
plating, of 4.5 mm/.177" diameter. Lead "Round Balls" are manufactured
in numerous calibers too; these are often 4.5 mm/.177" diameter and
designed for use in .177 caliber rifled guns normally used for shooting
pellets. Steel BBs can be acceptably accurate at short distances when
fired from properly designed BB guns with smoothbore barrels. Lead
number 3 buckshot pellets can be used in .25" caliber airguns as if they
were large BBs.
Due to the hardness of the steel, they can not
"take" to rifled barrels, which is why they are undersized (4.4 against
4.5 mm) to allow them to be used in .177" rifled barrels, which when
used in this configuration can in effect be considered smoothbore, but
with a poorer gas-seal. Were they 4.5 mm diameter, they would jam in the
bore. Therefore BB's lack the spin stabilization required for
long-range accuracy, and usage in any but the cheapest rifled guns is
discouraged.
Typically BBs are used for indoor practice, casual
outdoor plinking, training children, or for Air Gun / Air Rifle
enthusiasts who like to practice, but cannot afford high-powered Air Gun
/ Air Rifle systems that use pellets. Some shotgunners use sightless BB
rifles to train in instinctive shooting. Similar guns were also used
briefly by the United States Army in a Vietnam-era instinctive shooting
program called "Quick Kill" (Time magazine, Friday, July 14, 1967).
Darts and arrows
Air
guns can also fire darts or arrows using a similar mechanism to a
pneumatic nail gun.[11] This type of Air Gun / Air Rifle is usually
homebuilt and typically uses various high-pressure tanks as its power
source, ranging from oxygen tanks to fire extinguisher. Only Smoothbore
barrels are recommended for air dart ammunition. These are usually
limited to .177 cal.
Calibers
The most common Air Gun / Air Rifle calibers are
.177 (4.5 mm): the most common caliber. All official shooting
organizations mandate .177 caliber for both pistol and rifle
competition. Used in ISSF shooting events at the Olympic Games. It has
the flattest trajectory of all the calibers for a given energy level,
making accuracy simpler. At suitable energy levels it can be used
effectively for hunting.
.22 (5.5 mm & 5.6 mm): for hunting and general use.
Other less common traditional calibers include:
.20 (5 mm): initially proprietary to the Sheridan multi-pump pneumatic air rifle, later more widely used.
.25 (6.35 mm): the largest commonly available caliber for most of the 20th century.
Larger
caliber air rifles suitable for hunting large animals are offered by
major manufacturers. These are usually PCP guns. The major calibers
available are:
.357
.45 (11.43 mm)
.50 (12.7 mm)
.58 (14.5 mm)
Custom air guns are available in even larger calibers such as 20 mm (0.79") or .87 (22.1 mm.