Tank gun

Modern tank guns are high-velocity, large-caliber artilleries capable of firing kinetic energy penetrators, high-explosive anti-tank, and cannon-launched guided projectiles.

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.

The early British Mark I tanks of 1916 used two naval 57 mm QF 6 pounder Hotchkiss mounted either side in sponsons.

The first German tank, the A7V, used British-made 57 mm Maxim-Nordenfelt fortification guns captured from Belgium and Russia, mounted singly at the front.

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.

These weapons lacked a good high-explosive shell for attacking infantry and fortifications, but were effective against the light armor of the time.

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.

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).

Fighting capability at night, in poor weather, and smoke was improved by infrared, light-intensification, and thermal imaging equipment.

The best traditional antitank weapons have been kinetic energy rounds, whose penetrating power and accuracy is greatly decreased with the loss in muzzle velocity at extended range.

In the 1960s, smoothbore tank guns were developed by the United States, the Soviet Union, and later by the experimental American-West German MBT-70 joint project.

High-precision smoothbore tank gun barrels were perfected by the US Army's Weapons Laboratory at the Watervliet Arsenal based on a pair of patents by inventor Albert L. de Graffenried.

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.