Editing Shell (projectile) (section)

==Sizes==
{{See also|British standard ordnance weights and measurements|List of British ordnance terms}}

[[File:British crew preparing 155 mm shells Italy 22-02-1945 IWM NA 22473.jpg|thumb|left|British gun crew preparing 155 mm shells at Vergato, Italy during the [[Liberation of Italy]], 22 February 1945]]

The [[caliber]] of a shell is its [[diameter]]. Depending on the historical period and national preferences, this may be specified in [[millimeter]]s, [[centimeter]]s, or [[inch]]es. The length of gun barrels for large [[cartridge (firearms)|cartridges]] and shells (naval) is frequently quoted in terms of the ratio of the barrel length to the bore size, also called [[Caliber (artillery)|caliber]]. For example, the [[16"/50 caliber Mark 7 gun]] is 50 calibers long, that is, 16"×50=800"=66.7 feet long. Some guns, mainly British, were specified by the weight of their shells (see below).

Explosive rounds as small as [[Breda-SAFAT machine gun|12.7 x 82]] mm and [[MG 131 machine gun|13 x 64]] mm have been used on aircraft and armoured vehicles, but their small explosive yields have led some nations to limit their explosive rounds to [[20mm]] (.78 in) or larger. International Law precludes the use of explosive ammunition for use against individual persons, but not against vehicles and aircraft.  The largest shells ever fired during war were those from the German super-[[railway gun]]s, [[Schwerer Gustav|Gustav and Dora]], which were 800&nbsp;mm (31.5&nbsp;in) in caliber. Very large shells have been replaced by [[rocket]]s, [[missiles]], and [[bomb]]s. Today shells exceeding [[155 mm]] (6.1&nbsp;in) are much less commonly used, with the exception of certain dated legacy systems. The 203mm Soviet-era [[2S7 Pion]] is a noteworthy example, seeing regular usage throughout the [[Russo-Ukrainian War]] by the armed forces of both countries. Ukraine was able to continue fielding these heavy howitzers thanks to 203mm shells donated by the US, formerly used by the now-retired [[M110 howitzer]].<ref>{{Cite web |last=Vandenbosch |title=Ukraine Faces Ammunition Shortage for Its 2S7 Pion Self-Propelled Howitzers |url=https://armyrecognition.com/focus-analysis-conflicts/army/conflicts-in-the-world/russia-ukraine-war-2022/ukraine-faces-ammunition-shortage-for-its-2s7-pion-self-propelled-howitzers |access-date=2025-03-09 |website=armyrecognition.com |language=en-gb}}</ref>

[[File:US Army WWII field artillery.jpg|thumb|American soldiers with 155 mm artillery shells, 10 March 1945]]
Gun calibers have standardized around a few common sizes, especially in the larger range, mainly due to the uniformity required for efficient military logistics. Shells of 105 and 155&nbsp;mm for artillery with 105 and 120&nbsp;mm for tank guns are common in [[NATO]] allied countries. Shells of 122, 130, and 152&nbsp;mm for artillery with 100, 115, and 125&nbsp;mm for tank guns, remain in common usage among the regions of Eastern Europe, Western Asia, Northern Africa, and Eastern Asia. Most common calibers have been in use for many decades, since it is [[logistics|logistically]] complex to change the caliber of all guns and ammunition stores.

The weight of shells increases by and large with caliber. A typical 155&nbsp;mm (6.1&nbsp;in) shell weighs about 50&nbsp;kg (110 lbs), a common 203&nbsp;mm (8&nbsp;in) shell about 100&nbsp;kg (220 lbs), a concrete demolition 203&nbsp;mm (8&nbsp;in) shell 146&nbsp;kg (322 lbs), a 280&nbsp;mm (11&nbsp;in) battleship shell about 300&nbsp;kg (661 lbs), and a 460&nbsp;mm (18&nbsp;in) battleship shell over 1,500&nbsp;kg (3,307 lbs). The [[Schwerer Gustav]] [[large-calibre artillery|large-calibre gun]] fired shells that weighed between 4,800&nbsp;kg (10,582 lbs) and 7,100&nbsp;kg (15,653 lbs).

During the 19th century, the British adopted a particular form of designating artillery. Field guns were designated by nominal standard projectile weight, while howitzers were designated by barrel caliber. British guns and their ammunition were designated in [[pound (mass)|pound]]s, e.g., as "two-pounder" shortened to "2-pr" or "2-pdr". Usually, this referred to the actual weight of the standard projectile (shot, shrapnel, or high explosive), but, confusingly, this was not always the case.

Some were named after the weights of obsolete projectile types of the same caliber, or even obsolete types that were considered to have been functionally equivalent. Also, projectiles fired from the same gun, but of non-standard weight, took their name from the gun. Thus, conversion from "pounds" to an actual barrel diameter requires consulting a historical reference. A mixture of designations were in use for land artillery from the First World War (such as the [[BL 60-pounder gun]], [[RML 2.5 inch Mountain Gun]], 4 inch gun, 4.5 inch howitzer) through to the end of World War II (5.5 inch medium gun, [[Ordnance QF 25-pounder|25-pounder gun-howitzer]], 17-pounder tank gun), but the majority of naval guns were by caliber. After the end of World War II, field guns were designated by caliber.