Shell projectile: Encyclopedia II - Shell projectile - Types

Shell projectile - Types

There are many different types of shells. The principal ones include:

Shell projectile - High explosive HE

The most common shell type is high explosive, commonly referred to simply as HE. HE shells have a strong steel case, a bursting charge, and a fuze. When the fuze initiates the shell, the bursting charge shatters the case and scatters hot, sharp fragments of steel at high speed. Most of the damage is caused by being struck by these fragments, rather than directly by the blast. Depending on the type of fuze used the HE shell can be set to burst on the ground, in the air above the ground, or after penetrating a short distance into the ground (either to transmit more ground shock to covered positions, or to reduce the spread of fragments).

Shell projectile - Armour-piercing AP

In naval warfare and older anti-tank shells, the shell had to withstand the shock of punching through armour plate. Shells designed for this purpose had a greatly strengthened case with a specially hardened and shaped nose, and a much smaller bursting charge or even no bursting charge for smaller calibres. A further refinement of the design improved penetration by adding a softer metal cap to the penetrating nose giving APC (Armour piercing - capped). The softer cap took away some of the initial shock that would otherwise shatter the round. However the best profile for the cap was not the best for flight. To restore aerodynamics a further hollow cap was added to give APCBC (APC + Ballistic Cap). Explosive AP shells were sometimes distinguished by appending the suffix "-HE" or "/HE". Solid shot AP projectiles were so uncommon, that for unnecessary repetition the suffix "-HE" is usually not used; all projectiles can be assumed to have even small explosive charge. Plain AP shell is now very rarely seen except in naval usage, and is uncommon even there. See also: Armor-piercing shot and shell

Shell projectile - Armour-piercing discarding sabot APDS

APDS was developed by the United Kingdom and put into British service in March 1944 with their 6 pdr and 17 pdr anti-tank guns. For increased penetrating power a high velocity round was required, this in turn required a stronger material (such as tungsten) to withstand the greater shock of impact. Such a shot was too heavy at full bore to be accelerated to a sufficient muzzle velocity, so a lightweight outer carrier, the Sabot, (a French word for a wooden shoe) which filled the barrel was fitted around the smaller-diameter shot. This gives the projectile a higher acceleration in the gun's barrel, due to the larger surface area for the gases to impinge upon relative to its weight. Once outside the barrel, the sabot is stripped off by a combination of centripetal force and aerodynamic force, giving the shot low drag in flight. For a given caliber, this type of ammunition can effectively double the anti-tank performance of a gun over those using "simple" shot.

A kinetic energy penetrator that is a cross between APDS and APFS (armour-piercing, fin-stabilized) is APFSDS (armour-piercing, fin stabilized, discarding sabot). In this the projectile is made long and thin to increase its sectional density and thus penetration. However once a projectile is more than about ten times longer than it is wide, spin stabilisation becomes ineffective, so the projectile is instead stabilised by fins attached at its base, and is fired from an unrifled barrel. An APFSDS projectile looks like a big metal arrow. APFSDS projectiles are often made from tungsten alloys, but depleted uranium offers greater penetration.

APDS, APFS, and APFSDS rounds are solid "shot" and contain no explosive charge and are not therefore "shells".

Shell projectile - Armour-Piercing Composite Rigid APCR APCRBC

Developed around the same time as APDS. A solid high-density metal core (eg tungsten surrounded by a full bore shell of lighter material. This gave a full size bore for the purposes of giving the shot velocity in the barrel but at the point of impact the weight (and hence kinetic energy) was concentrated in the narrow core which struck the vehicle armour - the outer core generally left outside the armour.

A futher enhancement was to add a ballistic cap to the front of the shell over the core, to give the round a better ballistic shape and thereby lower drag and increase terminal velocity. This was referred to as APCRBC, for APCR Armour-piercing, Composite Rigid, Ballistic Cap

The same shell structure was used for "squeeze-bore" gun rounds. The softer outer core was compressed in the tapered section of the gun barrel resulting in a thinner projectile with better aerodynamic properties. See also Littlejohn adaptor.

Shell projectile - High explosive anti-tank HEAT

HEAT shells are a type of shaped charge used to defeat armoured vehicles. They are extremely efficient at defeating plain steel armour but are becoming less useful with the growing prevalence of composite and reactive armour. The power of the shell is independant of the velocity of the shell and is as effective at 1000 metres as at 100 metres. A HEAT charge is most effective when detonated at a certain, optimal, distance in front of the target and HEAT shells are usually distinguished by a long, thin nose probe sticking out in front of the rest of the shell, e.g., PIAT bomb.

Shell projectile - High explosive squash head HESH or high explosive plastic HEP

HESH is another anti-tank shell based on the use of explosive. Developed by the British inventor Sir Charles Dennistoun Burney in WW2 for use against fortifications. A thin case contains a charge of a plastic explosive. On impact the explosive flattens against the face of the armour. The fuze then detonates. Energy is transferred through the armour plate. When the compressive shock reflects off the air/metal interface on the inner face of the armour, it is transformed into a tension wave which spalls a "scab" of metal off into the tank damaging the equipment and crew without actually penetrating the armour.

HESH is completely defeated by spaced armour (provided that the plates are individually able to withstand the explosion), but remains popular because not all vehicles are equipped with spaced armour, and it is also the most efficient weapon for demolishing brick and concrete.

Shell projectile - Cluster shells

Like cluster bombs, an artillery shell may be used to scatter smaller submunitions, including anti-personnel grenades, anti-tank top-attack munitions, and landmines. These are generally far more lethal against both armor and infantry than simple high explosive shells, since the multiple munitions create a larger kill zone and increase the chance of achieving the direct hit necessary to kill armor. Most modern armies make significant use of cluster munitions in their artillery batteries.

Artillery-scattered mines allow for the quick deployment of minefields into the path of the enemy without placing engineering units at risk, though artillery delivery may lead to an irregular and unpredictable minefield with more duds than if mines were individually emplaced. Signatories of the Ottawa Treaty have renounced the use of artillery-scattered mines.

Shell projectile - Chemical

Chemical shells contain just a small explosive charge to burst the shell, and a larger quantity of a chemical weapon such as a poison gas. Signatories of the Chemical Weapons Convention have renounced such shells.

Shell projectile - Non-lethal shells

Not all shells are designed to kill or destroy. The following three types are designed to achieve particular non-lethal effects on the battlefield. They are not completely harmless, however; smoke and illumination shells can accidentally start fires, while all three types can cause minor damage (or potentially kill) if property or a person is unlucky enough to be struck by the discarded carrier.

The smoke shell is designed to create a smokescreen. The main types are bursting (usually filled with white phosphorus, WP) and base ejection (a shell which scatters smoke grenades).

Another non-lethal shell type is illumination. An illumination shell has a fuze which ejects the "candle" (a pyrotechnic flare emitting white, coloured, or infrared light) at a calculated altitude, where it slowly drifts down beneath a heat resistant parachute. These are also known as starshell.

The carrier shell is simply a hollow carrier equipped with a fuze which ejects the contents at a calculated time. They are often filled with propaganda leaflets (see external links), but can be filled with anything that meets the weight restrictions and is able to withstand the shock of firing. Famously, on Christmas Day 1899 during the siege of Ladysmith, the Boers fired into Ladysmith a carrier shell without fuze, which contained a Christmas pudding, two Union Jacks and the message "compliments of the season". The shell is still kept in the museum at Ladysmith.

Aerial firework bursts are created by shells. In the United States, consumer firework shells may not exceed 1.75 inches in diameter.

Adapted from the Wikipedia article "Types", under the G.N U Free Docmentation License. Please also see http://en.wikipedia.org/wiki