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 (AP, APCR, APCNR, APDS, APFSDS and proof shot). Besides, the projectile(shell) is the munitions or "bullet" fired downrange. This may or may not be an explosive device. Traditionally, projectiles have been classified as "shot" or "shell", the former being solid and the latter having some form of "payload".
The characteristics of shells are usually has large caliber projectiles fired by artillery, armored fighting vehicles (including tanks), and warships, usually have the shape of a cylinder topped by an olive-shaped nose for good aerodynamic performance, possibly with a tapering base, but some specialized types are quite different.
Next, shells can be divided into three configurations. Those are bursting, base ejection and nose ejection. Firstly, the most modern is base ejection, which was introduced in World War I. Dual purpose improved conventional munitions (DPICM)-bomblet, scatterable mines, illuminating, coloured flare, smoke, incendiary, propaganda, chaff (foil to jam radars: originally known as "window") and modern exotics such as electronic payloads and sensor-fuzed munitions. Next, the configuration is nose ejections that are shrapnel, flechette, star and incendiary. Both base and nose ejection are almost always used with airburst fuzes. Then, bursting shells use various types of fuze depending on the nature of the payload and the tactical need at the time. High-explosive, colored marker, chemical, nuclear devices; high explosive anti-tank (HEAT) and canister may be considered special types of bursting shell.
Artillery shells fired from a barrel can be assisted to greater range in three ways. Firstly, rocket assisted projectiles (RAP) enhance and sustain the projectile's velocity by providing additional 'push' from a small rocket motor that is part of the projectile's base. Next, Base bleed uses a small pyrotechnic charge at the base of the projectile to introduce sufficient combustion products into the low-pressure region behind the base of the projectile responsible for a large proportion of the drag. Lastly, ramjet assisted, similar to rocket assisted but using a ramjet instead of a rocket motor; it is anticipated that a ramjet-assisted 120-mm mortar shell could reach a range of 22 mi (35 km).
There are three states for Projectile (shell) stabilization. Firstly, Rifled Traditionally that is the artillery projectiles have been spin-stabilized, meaning that they spin in flight so that gyroscopic forces prevent them from tumbling. Spin is induced by gun barrels having rifling which engages a soft metal band around the projectile, called a "driving band" (UK) or "rotating band" (U.S.). The driving band is usually made of copper, but synthetic materials have also been used. In modern artillery smoothbore tubes have been used mostly by mortars. These projectiles use fins in the airflow at their rear to maintain correct orientation. The primary benefit over rifled barrels is reduced barrel wear and longer ranges that can be achieved (due to the reduced loss of energy to friction and gas escaping around the projectile via the rifling). Lastly, Rifled/Fin-Stabilized that is a combination of the above can be used, where the barrel is rifled, but the projectile also has deployable fins for stabilization, guidance or gliding.
There are main functions in the field artillery system are which are Communications, Command: authority to allocate resources, Target acquisition: detect, identify and deduce the location of targets, Control: authority to decide which targets to attack and allot fire units to the attack, Production of firing data – to deliver fire from a fire unit onto its target, Fire units: guns, launchers or mortars grouped together, Specialist services – produce data to support the production of accurate firing data, Logistic services – to provide combat supplies, particularly ammunition, and equipment support.
