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GENERAL HISTORY

A tank gun is the main armament of a tank. They are usually large-caliber guns that fire different types of projectiles at different velocities. Their history goes back in time way before the first tank even rolled on the battlefield.

A British Mark I tank captured by German forces. The 57 mm Hotchkiss gun is on its left.

The concept of a long-barreled gun that could fire a simple metal projectile dates back to the times when naval artillery technology was advancing at astonishing rates.

The first tank gun was mounted, of course, on the first tank, the British Mark I that first saw action during the Battle of the Somme in 1916. It used a very simple 57 mm Hotchkiss naval gun. While it didn't meet too many tanks, the Hotchkiss proved to be useful in breakthroughs and even against infantry.

The concept of the modern tank gun would only appear after World War I. By the 1930's, tank guns became more and more complex. Projectile penetrators featured increased velocity and grew in caliber, a direct effect of the introduction of better armor.

World War II was the golden age of tank gun development. This is the time when smoothbore howitzers and concepts such as the Little John adapter or Konisch gun barrel became a thing.

A German Panzer IV. The long-barreled 75 mm gun can be easily seen here.

During the Cold War, the typical tank gun also featured a bore extractor and, in most instances, got rid of the typical muzzle brake.

An M1 Abrams firing its main 120 mm smoothbore gun. Bore extractor can be seen here, being mounted close to the middle section of the barrel.

IN SIMPLEPLANES

Tank guns look like your average wing gun with the exception that they are highly customizable. They featured a smooth barrel with a simple gun breech at the back.
Among the customizable features we have:

• Caliber. Ranging from as little as 12.7 mm to as much as 800 mm.

• Nominal barrel length. Defined as the actual barrel length (not the external one) and calculated in lengths of caliber.
  For instance, a 120 mm L/44 gun is 44 x 120 mm in length.

• Main shell types. Only three types of shells can be used. You can easily switch between them via an on-screen button or key assigned to it. You can choose between AP, HE, APCR, HEAT, APDS and HESH ammo.

  1. AP is a jack-of-all-trades-master-of-none. Decent power and velocity.
  2. HE has immense power but is rather poor in terms of velocity.
  3. APCR is essentially a tungsten core wrapped in a copper shell. Loses velocity quickly but has immense penetration power.
  4. HEAT is a chemical-type penetrator. A hot stream of melting metal pierces through a relatively small hole. Slow velocity.
  5. APDS is a wartime British penetrator. Once the shell leaves the barrel, a tungsten sabot is released from its outer shell. Works just like APCR but can only be used in anti-armor roles.
  6. HESH is also another British type of shell. A squash head (essentially a shaped charge) explodes upon impact.

• Type of gun. It can be single-shot, autocannon (fires a salvo of shells) and autoloader.

The autoloader works a bit different from the autocannon. The gun is fed from a drum filled with X shells. Once the drum is empty, only then it will reload (R key/on-screen button).

• Loading type. You can choose between mechanically-assisted and manual loading. Loading times may vary by +/-1 second with manual loading but aren't prone to failures while mechanical loading may vary by +/- 0.3 seconds and can break down.

• Muzzle brake/bore extractor. You can also choose between different types of muzzle brakes.
  Here, for instance, is a common muzzle brake design used by the US during WW II.
  

FINAL THOUGHTS

While, by name, we imply that they can only be used as tank guns, you can also use them on ships. There is a certain limit for gun length (L/100) as weight gradually increases. Big guns require big platforms.

A big pro about tank guns is that they aren't too hard to implement. Much of the work is already done in the form of wing guns.

While I haven't mentioned it, shells do experience dropoff as they fly.

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