Editing Artillery (section)

===Propellant===
[[File:152 mm howitzer D-20 belong to Military of Iran.jpg|thumb|right|upright=1.05|[[152 mm towed gun-howitzer M1955 (D-20)|152 mm howitzer D-20]] during the [[Iran–Iraq War]]]]
Most forms of artillery require a [[propellant]] to propel the projectile to the target. Propellant is always a low explosive, which means it [[Deflagration|deflagrates]], rather than [[detonation|detonating]] like high explosives. The shell is accelerated to a high velocity in a very short time by the rapid generation of gas from the burning propellant. This high pressure is achieved by burning the propellant in a contained area, either the chamber of a gun barrel or the combustion chamber of a [[rocket motor]].

Until the late 19th century, the only available propellant was [[black powder]]. It had many disadvantages as a propellant; it has relatively low power, requiring large amounts of powder to fire projectiles, and created thick clouds of white smoke that would obscure the targets, betray the positions of guns, and make aiming impossible. In 1846, [[nitrocellulose]] (also known as guncotton) was discovered, and the high explosive [[nitroglycerin]] was discovered at  nearly the same time. Nitrocellulose was significantly more powerful than black powder, and was smokeless. Early guncotton was unstable, however, and burned very fast and hot, leading to greatly increased barrel wear. Widespread introduction of smokeless powder would wait until the advent of the double-base powders, which combine nitrocellulose and nitroglycerin to produce powerful, smokeless, stable propellant.

Many other formulations were developed in the following decades, generally trying to find the optimum characteristics of a good artillery propellant – low temperature, high energy, non-corrosive, highly stable, cheap, and easy to manufacture in large quantities. Modern gun propellants are broadly divided into three classes: single-base propellants that are mainly or entirely nitrocellulose based, double-base propellants consisting of a combination of nitrocellulose and nitroglycerin, and triple base composed of a combination of nitrocellulose and nitroglycerin and [[nitroguanidine]].

Artillery shells fired from a barrel can be assisted to greater range in three ways:
* [[Rocket-assisted projectile]]s enhance and sustain the projectile's velocity by providing additional 'push' from a small rocket motor that is part of the projectile's base.
* [[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 [[Form drag|drag]].
* 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 {{convert|22|mi|km|abbr=on}}.<ref>{{cite book|last=McNab|first=Chris|author2=Hunter Keeter|title=Tools of Violence: Guns, Tanks and Dirty Bombs|publisher=Osprey Publishing|year=2008|page=[https://archive.org/details/toolsofviolenceg0000mcna/page/145 145]|isbn=978-1-84603-225-7|url=https://archive.org/details/toolsofviolenceg0000mcna/page/145}}</ref>

Propelling charges for barrel artillery can be provided either as cartridge bags or in metal cartridge cases. Generally, anti-aircraft artillery and smaller-caliber (up to 3" or 76.2&nbsp;mm) guns use metal cartridge cases that include the round and propellant, similar to a modern rifle cartridge. This simplifies loading and is necessary for very high rates of fire. Bagged propellant allows the amount of powder to be raised or lowered, depending on the range to the target. It also makes handling of larger shells easier. Cases and bags require totally different types of breech. A metal case holds an integral primer to initiate the propellant and provides the gas seal to prevent the gases leaking out of the breech; this is called obturation. With bagged charges, the breech itself provides obturation and holds the primer. In either case, the primer is usually percussion, but electrical is also used, and [[laser ignition]] is emerging. Modern 155&nbsp;mm guns have a primer magazine fitted to their breech.

[[File:16-in Battleship Ammunition.JPG|thumb|Battleship ammunition: 16" artillery shells aboard a United States {{sclass|Iowa|battleship}}]]
Artillery ammunition has four classifications according to use:
* '''Service''': ammunition used in [[live fire exercise|live fire training]] or for wartime use in a combat zone. Also known as "warshot" ammunition.
* '''Practice''': Ammunition with a non- or minimally-explosive projectile that mimics the characteristics (range, accuracy) of live rounds for use under training conditions. Practice artillery ammunition often utilizes a colored-smoke-generating bursting charge for marking purposes in place of the normal high-explosive charge.
* '''Dummy''': Ammunition with an inert warhead, inert primer, and no propellant; used for training or display.
* '''Blank''': Ammunition with live primer, greatly reduced propellant charge (typically black powder), and no projectile; used for training, demonstration or ceremonial use.