Driving band
Encyclopedia
The driving band or rotating band is part of an artillery
shell
, a band of soft metal near the middle of the shell, typically made of gilding metal
,http://www.gd-ots.com/sitepages/artillery.html copper
or lead
. When the shell is fired the pressure of the propellant swage
s the metal into the rifling of the barrel, both providing a seal preventing the gases from blowing past the shell, as well as engaging with the rifling
to spin-stabilize
the shell. In a rifle
, the entire bullet is typically covered in copper or a similarly soft alloy, so the entire bullet is its own driving band.
One downside to the driving band is that it must be placed at the widest point on the shell, and also near the balance point. This is not necessarily the best point from an aerodynamic perspective, at high supersonic speeds the widest point should be far to the rear of the balance point. Another issue is that with increasing shell weight it becomes more difficult to engineer the driving band. Instead of the propellant gases driving the shell up the barrel, it can simply blow the driving band right off the shell.
Some weapons that operate at high rates of fire, such as the GAU-8 Avenger
gatling cannon, use plastic driving bands rather than soft metal. The advantage in using plastic as a swage material in such cases is reduced wear on the barrel rifling, extending the life and average accuracy of the weapon.
.
Freely rotating bands can be used to reduce the amount of spin imparted to the round as is preferable for HEAT
warheads or fin stabilised projectiles.
Gerald Bull
worked extensively on ways to eliminate the driving band, leading to the development of his Extended Range, Full Bore ammunition using an inversion of the pre-cut rifling for his GC-45 howitzer
, which is now rapidly replacing older artillery worldwide.
Artillery
Originally applied to any group of infantry primarily armed with projectile weapons, artillery has over time become limited in meaning to refer only to those engines of war that operate by projection of munitions far beyond the range of effect of personal weapons...
shell
Shell (projectile)
A shell is a payload-carrying projectile, which, as opposed to shot, contains an explosive or other filling, though modern usage sometimes includes large solid projectiles properly termed shot . Solid shot may contain a pyrotechnic compound if a tracer or spotting charge is used...
, a band of soft metal near the middle of the shell, typically made of gilding metal
Gilding metal
Gilding metal is a copper alloy, comprising 95% copper and 5% zinc. Technically, it is a brass.Gilding metal is used for various purposes, including the jackets of bullets, driving bands on some artillery shells, as well as enameled badges and other jewellery....
,http://www.gd-ots.com/sitepages/artillery.html copper
Copper
Copper is a chemical element with the symbol Cu and atomic number 29. It is a ductile metal with very high thermal and electrical conductivity. Pure copper is soft and malleable; an exposed surface has a reddish-orange tarnish...
or lead
Lead
Lead is a main-group element in the carbon group with the symbol Pb and atomic number 82. Lead is a soft, malleable poor metal. It is also counted as one of the heavy metals. Metallic lead has a bluish-white color after being freshly cut, but it soon tarnishes to a dull grayish color when exposed...
. When the shell is fired the pressure of the propellant swage
Swage
Swaging is a forging process in which the dimensions of an item are altered using a die or dies, into which the item is forced. Swaging is usually a cold working process; however, it is sometimes done as a hot working process....
s the metal into the rifling of the barrel, both providing a seal preventing the gases from blowing past the shell, as well as engaging with the rifling
Rifling
Rifling is the process of making helical grooves in the barrel of a gun or firearm, which imparts a spin to a projectile around its long axis...
to spin-stabilize
Spin-stabilisation
Spin-stabilisation is the method of stabilizing a satellite or launch vehicle by means of spin. For most satellite applications this approach has been superseded by three-axis stabilisation. It is also used in non-satellite applications such as rifle and artillery.Despinning can be achieved by...
the shell. In a rifle
Rifle
A rifle is a firearm designed to be fired from the shoulder, with a barrel that has a helical groove or pattern of grooves cut into the barrel walls. The raised areas of the rifling are called "lands," which make contact with the projectile , imparting spin around an axis corresponding to the...
, the entire bullet is typically covered in copper or a similarly soft alloy, so the entire bullet is its own driving band.
One downside to the driving band is that it must be placed at the widest point on the shell, and also near the balance point. This is not necessarily the best point from an aerodynamic perspective, at high supersonic speeds the widest point should be far to the rear of the balance point. Another issue is that with increasing shell weight it becomes more difficult to engineer the driving band. Instead of the propellant gases driving the shell up the barrel, it can simply blow the driving band right off the shell.
Some weapons that operate at high rates of fire, such as the GAU-8 Avenger
GAU-8 Avenger
The General Electric GAU-8/A Avenger is a 30 mm, hydraulically-driven seven-barrel Gatling-type rotary cannon that is mounted on the United States Air Force's Fairchild Republic A-10 Thunderbolt II. It is among the largest, heaviest and most powerful aircraft cannons in the United States military...
gatling cannon, use plastic driving bands rather than soft metal. The advantage in using plastic as a swage material in such cases is reduced wear on the barrel rifling, extending the life and average accuracy of the weapon.
Variations
Driving bands pre-cut for the rifling have been used for muzzle loaded weapons, e.g. some mortarsMortar (weapon)
A mortar is an indirect fire weapon that fires explosive projectiles known as bombs at low velocities, short ranges, and high-arcing ballistic trajectories. It is typically muzzle-loading and has a barrel length less than 15 times its caliber....
.
Freely rotating bands can be used to reduce the amount of spin imparted to the round as is preferable for HEAT
Heat
In physics and thermodynamics, heat is energy transferred from one body, region, or thermodynamic system to another due to thermal contact or thermal radiation when the systems are at different temperatures. It is often described as one of the fundamental processes of energy transfer between...
warheads or fin stabilised projectiles.
Gerald Bull
Gerald Bull
Gerald Vincent Bull was a Canadian engineer who developed long-range artillery. He moved from project to project in his quest to launch economically a satellite using a huge artillery piece, to which end he designed the Project Babylon "supergun" for the Iraqi government...
worked extensively on ways to eliminate the driving band, leading to the development of his Extended Range, Full Bore ammunition using an inversion of the pre-cut rifling for his GC-45 howitzer
GC-45 howitzer
The GC-45 is a 155 mm howitzer designed by Gerald Bull's Space Research Corporation in the 1970s. Versions were produced by a number of companies during the 1980s, notably in Austria and South Africa...
, which is now rapidly replacing older artillery worldwide.