A driving band or rotating band is a band of soft metal near the base of an artillery shell, often made of gilding metal, [1] copper, or lead. When the shell is fired, the pressure of the propellant swages the metal into the rifling of the barrel and forms a seal; this seal prevents the gases from blowing past the shell and engages the barrel's rifling to spin-stabilize the shell.
The rotating band has three essential functions: [2]
The shell is stabilized for yaw in the barrel by a smaller bourrelet band near the front of the projectile. This band keeps the projectile travelling straight in the bore supported by the lands between the rifling grooves, but doesn't engage the rifling. [3]
As shell weight increases, it becomes more difficult to engineer a driving band that prevents propellant gases from either blowing past it, or blowing it off the shell. Tougher alloys like cupronickel may be used on major-caliber projectiles. Rotating band width of about one-third of the projectile caliber provides superior performance, but two narrower bands, separated by a short distance, have been used to conserve strategic metals in wartime. Each band is secured in a dovetailed notch machined into the projectile. Waved ridges, longitudinal nicks, or knurling is machined into the bottom of the notch to prevent the band from slipping around the projectile as the projectile accelerates down the gun barrel. The rotating band is made of a ring of slightly greater diameter than the projectile, slipped into position while thermally expanded, and pressed radially into place with a powerful hydraulic banding press. [2]
The forward edge of the band may be conically tapered to fit into a coned seat at the start of the gun barrel rifling. The central portion of the band is roughly cylindrical with a diameter slightly larger than the groove diameter of the gun barrel to ensure a tight fit in gun barrels worn by firing previous projectiles. The rear portion of the band may include a flared skirt of even larger diameter in front of a groove to hold the skirt as it is compressed by barrel dimensions. The skirt is intended to provide a gas seal in the most heavily eroded portion of the bore near the powder chamber. [2]
Driving bands pre-cut for the rifling have been used for muzzle loaded weapons, e.g. some mortars. Freely rotating bands can be used to reduce the spin imparted to the round as is preferable for HEAT warheads or fin-stabilised projectiles fired from general-purpose rifled barrels.
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.
Some weapons that operate at high rates of fire, such as the GAU-8 Avenger Gatling cannon, use plastic driving bands instead of soft metal. Using plastic as a swage material reduces wear on the barrel's rifling, and extends the life and average accuracy of the weapon.
In a small-arms rifle, the entire bullet is typically covered in copper or another soft alloy, making the entire bullet its own driving band.
During World War II, German ammunition sometimes used iron driving bands instead of copper due to material shortages. Porous iron bands were favored over solid ones. [4]
A rifle is a long-barreled firearm designed for accurate shooting and higher stopping power, with a barrel that has a helical or spiralling pattern of grooves (rifling) cut into the bore wall. In keeping with their focus on accuracy, rifles are typically designed to be held with both hands and braced firmly against the shooter's shoulder via a buttstock for stability during shooting. Rifles have been used in warfare, law enforcement, hunting and target shooting sports.
A bullet is a kinetic projectile, a component of firearm ammunition that is shot from a gun barrel. They are made of a variety of materials, such as copper, lead, steel, polymer, rubber and even wax; and are made in various shapes and constructions, including specialized functions such as hunting, target shooting, training, and combat. Bullets are often tapered, making them more aerodynamic. Bullet size is expressed by weight and diameter in both imperial and metric measurement systems. Bullets do not normally contain explosives but strike or damage the intended target by transferring kinetic energy upon impact and penetration.
Rotation of ammunition is a term used with reference to guns. Projectiles intended for RML guns were at first fitted with a number of gun-metal studs arranged around them in a spiral manner corresponding to the twist of rifling. Invented in mid-1840s by Giovanni Cavalli, this method was defective, as it allowed, as in the old smooth-bore guns, the powder gas to escape by the clearance between the projectile and the bore, with a consequent loss of efficiency; it also quickly eroded the bore of the larger guns. Multiple solution to the problems were invented in two following decades, both for muzzle-loaders and breech-loaders.
A cartridge, also known as a round, is a type of pre-assembled firearm ammunition packaging a projectile, a propellant substance and an ignition device (primer) within a metallic, paper, or plastic case that is precisely made to fit within the barrel chamber of a breechloading gun, for convenient transportation and handling during shooting. Although in popular usage the term "bullet" is often used to refer to a complete cartridge, the correct usage only refers to the projectile.
Rifling is the term for helical grooves machined into the internal surface of a firearms's barrel for imparting a spin to a projectile to improve its aerodynamic stability and accuracy. It is also the term for creating such grooves.
Muzzle velocity is the speed of a projectile with respect to the muzzle at the moment it leaves the end of a gun's barrel. Firearm muzzle velocities range from approximately 120 m/s (390 ft/s) to 370 m/s (1,200 ft/s) in black powder muskets, to more than 1,200 m/s (3,900 ft/s) in modern rifles with high-velocity cartridges such as the .220 Swift and .204 Ruger, all the way to 1,700 m/s (5,600 ft/s) for tank guns firing kinetic energy penetrator ammunition. To simulate orbital debris impacts on spacecraft, NASA launches projectiles through light-gas guns at speeds up to 8,500 m/s (28,000 ft/s). FPS and MPH are the most common American measurements for bullets. Several factors, including the type of firearm, the cartridge, and the barrel length, determine the bullet's muzzle velocity.
A sabot is a supportive device used in firearm/artillery ammunitions to fit/patch around a projectile, such as a bullet/slug or a flechette-like projectile, and keep it aligned in the center of the barrel when fired. It allows a narrower projectile with high sectional density to be fired through a barrel of much larger bore diameter with maximal accelerative transfer of kinetic energy. After leaving the muzzle, the sabot typically separates from the projectile in flight, diverting only a very small portion of the overall kinetic energy.
A gun barrel is a crucial part of gun-type weapons such as small firearms, artillery pieces, and air guns. It is the straight shooting tube, usually made of rigid high-strength metal, through which a contained rapid expansion of high-pressure gas(es) is used to propel a projectile out of the front end (muzzle) at a high velocity. The hollow interior of the barrel is called the bore, and the diameter of the bore is called its caliber, usually measured in inches or millimetres.
Internal ballistics, a subfield of ballistics, is the study of the propulsion of a projectile.
The Minié ball, or Minie ball, is a type of hollow-based bullet designed by Claude-Étienne Minié, inventor of the French Minié rifle, for muzzle-loading rifled muskets. It was invented in 1846 and came to prominence during the Crimean War and the American Civil War, where it was found to inflict significantly more serious wounds than earlier round musket balls. Both the American Springfield Model 1861 and the British Pattern 1853 Enfield rifled muskets, the most common weapons used during the American Civil War, used the Minié ball.
Obturation is the necessary barrel blockage or fit in a firearm or airgun created by a deformed soft projectile. A bullet or pellet made of soft material and often with a concave base will flare under the heat and pressure of firing, filling the bore and engaging the barrel's rifling. The mechanism by which an undersized soft-metal projectile enlarges to fill the barrel is, for hollow-base bullets, expansion from gas pressure within the base cavity and, for solid-base bullets, "upsetting"—the combined shortening and thickening that occurs when a malleable metal object is struck forcibly at one end.
Palliser shot is an early British armour-piercing artillery projectile, intended to pierce the armour protection of warships being developed in the second half of the 19th century. It was invented by Sir William Palliser, after whom it is named.
This article explains terms used for the British Armed Forces' ordnance (weapons) and ammunition. The terms may have different meanings depending on its usage in another country's military.
A bourrelet is a portion of an elongated artillery projectile that is used in conjunction with the projectile's driving band, or rotating band, to stabilize its launch by keeping the fore part of the projectile precisely aligned with the gun barrel.
Polygonal rifling is a type of gun barrel rifling where the traditional sharp-edged "lands and grooves" are replaced by less pronounced "hills and valleys", so the barrel bore has a polygonal cross-sectional profile.
A gas check is a gasket type component of firearms ammunition. Gas checks are used when non-jacketed bullets are used in high pressure cartridges. The use of a gas check inhibits the buildup of lead in the barrel and improves accuracy.
A pellet is a non-spherical projectile designed to be shot from an air gun, and an airgun that shoots such pellets is commonly known as a pellet gun. Air gun pellets differ from bullets and shot used in firearms in terms of the pressures encountered; airguns operate at pressures as low as 50 atmospheres, while firearms operate at thousands of atmospheres. Airguns generally use a slightly undersized projectile that is designed to obturate upon shooting so as to seal the bore, and engage the rifling; 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 a smoothbore barrel, they are often designed to be inherently stable, much like the Foster slugs used in smoothbore shotguns.
The following are terms related to firearms and ammunition topics.
In artillery, caliber or calibre is the internal diameter of a gun barrel, or, by extension, a relative measure of the barrel length.
In firearms, freebore is the portion of the gun barrel between the chamber and the rifled section of the barrel bore. The freebore is located just forward of the chamber neck and is cylindrical in shape. The diameter of the freebore is larger than the groove diameter of the gun barrel bore so that no rifling is present and projectiles used in the firearm can accelerate through the freebore without resistance.
