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.

Overview

Tank guns are a specific field of weapon design that meet the particular needs of the tank. 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 turret. 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 use self-contained ammunition, allowing rapid loading (or use of an autoloader).

History

The first tank guns were merely field artillery pieces stripped from their carriages and emplaced in turrets or sponsons on armored vehicles. They were generally short-barrelled weapons and fired typical artillery ammunition (primarily high explosive). This was effective in the anti-infantry and infantry support roles that tanks played in World War I. 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.

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, derivatives of the emerging anti-tank gun designs were modified to fit tanks. These weapons fired smaller shells, but fired them at higher velocities and more accurately, improving their performance against armor. Such light guns as the 2-pounder and 37mm equipped a number of tanks at the start of the war. However, these proved insufficient against more heavily armored tanks.

World War II saw leapfrog growth in all areas of military technology. Tank guns were no exception. As tanks became heavier and better protected, their weapons grew from 37mm to 50mm to 75mm to 90mm. Shells were improved to provide better penetration with harder materials and scientific shaping. All of these meant lethal 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.

The larger caliber, shorter range artillery mounting didn't go away however. In fact, such weapons were the favored mount for infantry tanks, upon which rested the job of taking out emplacements and infantry concentrations with their heavy high explosive shells.

After World War II, the race to increase caliber slowed. Slight increases were made between tank generations. In the West, the 90mm gun gave way to the 105mm, which gave way to the 120mm in the 60's. In the East, the 85mm quickly yielded to the 100mm and 115mm gun, with the 125mm caliber now standard. Most of the improvements were instead made in the ammunition and in fire control systems.

In kinetic energy penetrators, solid shot and armour-piercing shell gave way to armour-piercing discarding sabot (APDS), and fin-stabilized (APFSDS) rounds with tungsten or depleted uranium penetrators. Parallel developments brought in High Explosive Squash-Head (HESH), and shaped-charge High Explosive Anti-Tank (HEAT) rounds as alternatives.

Stadiametric range-finders were successively replaced by coincidence and laser range-finders. Accuracy of modern tank guns is pushed to the limits by computerized fire control systems, wind sensors, and muzzle referencing systems which compensate for barrel warping and wear. Fighting capability at night, in poor weather and smoke was improved by infrared, light-intensification, and thermal imaging equipment.

However, a few innovations have also been made in gun technology.

Throughout the history of tank guns, they have almost exclusively been rifled weapons. Rifling of the barrel imparts spin on the projectile, improving ballistic accuracy. The best traditional antitank weapons have been kinetic energy rounds, whose penetrating power and accuracy decrease with range. For longer ranges, high explosive anti-tank rounds are better, but accuracy still suffers. At extremely long ranges, anti-tank guided missiles (ATGMs) are considered to have a better chance of hitting the target.

In the 1960s smoothbore tank guns were developed by the Soviet Union and by the experimental U.S.–German MBT-70 project. The U.S. introduced a low-pressure 152mm smoothbore gun which also launched ATGMs. This weapon was employed in the M551 Sheridan light tank and the short-lived M60A2, but the system suffered serious teething pains and the gun/launcher concept has since been abandoned by the U.S. Based on their experience with the less-capable gun/missile system of the BMP-1, the Soviets produced the T-64B main battle tank, with an auto-loaded 125mm 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 and Ukrainian T-84 MBTs. German company Rheinmetall developed a more conventional 120mm smoothbore tank gun which does not fire missiles, adopted for the Leopard 2, and later the U.S. M1 Abrams.

The recent Russian 'Black Eagle' prototype, shown at some arms exhibitions, reportedly can be equipped with a 152mm tank gun.

The near future of the tank gun does not look likely to hold many revolutionary developments. Whereas, in the past, caliber had been limited by technological issues, now they are as large as reasonable to fit on vehicles in the size class of today's main battle tanks. Instead, the emphasis is on the electronics and the ammunition more than ever. A focus on crew survivability and technology may also lead to more tank guns with autoloaders, mounted in remote controlled turrets or on light vehicles, like the proposed Mobile Gun System.