page_title: Tank gun
section_title: Smoothbore
hierarchical_section_title: Tank gun / Smoothbore
caption_attribution_description: English: The inside of a Rheinmetall 120 mm gun (seen from the muzzle) of a Leopard 2A4 Deutsch: Das Innere einer Rheinmetall 120-mm-Glattrohrkanone (gesehen von der Mündung aus) eines Leopard 2A4
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: In the 1960s smoothbore tank guns were developed by the Soviet Union and later by the experimental US–FRG MBT-70 project. Based on their experience with the gun/missile system of the BMP-1, the Soviets produced the T-64B main battle tank, with an auto-loaded 2A46 125 mm smoothbore high-velocity tank gun, capable of firing APFSDS ammunition as well as ATGMs.  Similar guns continue to be used in the latest Russian T-90, Ukrainian T-84, and Serbian M-84AS MBTs. The German company Rheinmetall developed a more conventional 120 mm smoothbore tank gun which can fire LAHAT missiles, adopted for the Leopard 2, and later the U.S. M1 Abrams. The chief advantages of smoothbore designs are their greater suitability for fin stabilised ammunition and their greatly reduced barrel wear compared with rifled designs. Much of the difference in operation between smoothbore and rifled guns shows in the type of secondary ammunition that they fire, with a smoothbore gun being ideal for firing HEAT rounds (although specially designed HEAT rounds can be fired from rifled guns) and rifling being necessary to fire HESH rounds.
  Most modern main battle tanks now mount a smoothbore gun. A notable exception are the tanks of the British Army which used the 120mm Royal Ordnance L11A5 rifled gun until the 1990s; it was then replaced it with the 120mm L30 rifled gun which remains in service. The Indian Arjun tank uses an Indian-developed 120mm rifled gun.
caption: The inside of a Rheinmetall 120 mm smoothbore tank gun (seen from the muzzle) of a Leopard 2A4.
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