page_title: Tank gun
section_title: World War II
hierarchical_section_title: Tank gun / History / World War II
caption_attribution_description: Deutsch: Panzerkampfwagen IV, Ausführung J ausgestellt im Museum des Blindés in Saumur. English: PzKpfw IV, version J on display at the Musée des Blindés in Saumur. Русский: Немецкий средний танк "Pz.Kpfw. IV версия Х"
context_page_description: A tank gun is the main armament of a tank. Modern tank guns are large-caliber high-velocity guns, capable of firing kinetic energy penetrators, high explosive anti-tank rounds, and in some cases guided missiles. Anti-aircraft guns can also be mounted to tanks.
  As the tank's primary armament, they are almost always employed in a direct fire mode to defeat a variety of ground targets at all ranges, including dug-in infantry, lightly armored vehicles, and especially other heavily armored tanks. They must provide accuracy, range, penetration, and rapid fire in a package that is as compact and lightweight as possible, to allow mounting in the cramped confines of an armored gun turret. Tank guns generally use self-contained ammunition, allowing rapid loading. They often display a bulge in the barrel, which is a bore evacuator, or a device on the muzzle, which is a muzzle brake.
context_section_description: This thinking remained pervasive into the dawn of World War II, when most tank guns were still modifications of existing artillery pieces, and were expected to primarily be used against unarmored targets.  The larger caliber, shorter range artillery mounting did not go away however. Tanks intended specifically for infantry support (the infantry tanks), expected to take out emplacements and infantry concentrations,  carried large calibre weapons to fire large high-explosive shells—though these could be quite effective against other vehicles at close ranges. In some designs - for example, M3 Lee, Churchill, Char B1 - the larger bore weapons were mounted within the tank hull while a second gun for use against tanks was fitted in a turret.
  However, other strategists saw new roles for tanks in war, and wanted more specifically developed guns tailored to these missions.  The ability to destroy enemy tanks was foremost on their minds.  To this end, the emerging anti-tank gun designs were modified to fit tanks.  These weapons fired smaller shells, but at higher velocities with higher accuracy, improving their performance against armor.  Such light guns as the QF 2-pounder (40 mm) and 37 mm equipped British cruiser tanks and infantry tanks in the late 1930s.  These weapons lacked a good high-explosive shell for attacking infantry and fortifications, but were effective against the light armor of the time.
  World War II saw a leapfrog growth in all areas of military technology. Battlefield experience led to increasingly powerful weapons being adopted. Guns with calibres from 20 mm to 40 mm soon gave way to 50 mm, 75 mm, 85 mm, 88 mm, 90 mm and 122 mm calibre. In 1939, the standard German panzer had either a 20 mm or 37 mm medium-velocity weapon, but by 1945 long-barrelled 75 mm and 88 mm high-velocity guns were common. The Soviets introduced their 122 mm in a turreted heavy tank series, the Iosef Stalin tanks. Shells were improved to provide better penetration with harder materials and scientific shaping.  All of these meant improvements in accuracy and range, although the average tank had to grow as well to carry the ammunition, mounting, and protection for these powerful guns.
  While high velocity tank guns were effective against other tanks, for the most part British tanks moved to a dual purpose 75 mm gun capable of firing a useful HE shell; later in the war adding 76mm 17pdr gun armed tanks for better antitank capability.
  Many nations devised "tank destroyers" during the war - a vehicle specifically designed for anti-tank work, and armed more heavily than a tank on the same chassis could be. They generally fell into three overlapping categories: improvised modifications of old or captured tanks to render them viable again (such as converting the machine-gun-only Panzer I into the Panzerjäger I), often with haphazard, poorly protected, limited-traverse weapon mounts; the American offensive and mobile reserve model, which favoured lightly-armed open-top vehicles with a rotating turret and a powerful anti-tank-capable gun while relegating true tanks to infantry support role (exemplified by the M10 tank destroyer); and the casemate gun mount model, which often allowed the resultant vehicle to be hard to hit and have a well-sloped and heavily armoured glacis plate (for instance, the SU-100). The relative superiority in armament of tank destroyers was only relative, however: for instance, the SU-85 was a casemate-type TD on the T-34 chassis that was rendered obsolete once the basic T-34 switched from the 76 mm gun to the same 85 mm cannon, producing the T-34-85.
caption: The long-barrelled 75 mm gun of this Panzer IV is typical of larger late WWII designs built to destroy heavily armored tanks.
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