Calibers above 300 mm are a BAD idea, and above 200mm you need to add drawbacks for anything which isn't a ship.
And your description needs improvement, but that might be related to your age and experience with English language, (it is easier to write a long description when you are older, have more experience with writing and become better in English).
So, Tsar Cannon, Take Two.
Faction: All Epsilon factions
Requires: Epsilon War Factory, Infiltration of an Epsilon ConYard
Weapon: 250mm Gauss Cannon
Armor Class: Heavy
Strength: Very high
Cost: Around Centurion's
Note: Immune to mind control and poison.
Vehicles close to this thing get slowed down and lose firepower, no matter their allegiance. EMP mines explode when this vehicle is within three tiles of them.
When Yuri was working for the Russians, he found blueprints for a huge Soviet tank, much bigger than everything else existing back then. It carried a powerful cannon, but was very clumsy in usage, which explains why the Russians never used it. The Chinese however, also copied the blueprints, but in the end only used the cannon, which still has its use on the Centurion Siege Crawlers.
Yuri, however, took a different approach. He always loved high tech equipment and was personally involved with the development of the Railgun used by the Railgun Tower and the Marauder. This tank would not use a Railgun, but a fairly similar weapon, a Gauss rifle. Instead of firing shell-shaped iron projectiles like Railguns, this tank would fire round shot filled with stable explosives (explosives too unstable could explode in the barrel when the projectile gained speed) for maximum damage against structures and groups of infantry, and Yuri knew that the speed and heavy weight of the projectile would ensure tanks would take massive damage as well.
The huge power of the resulting 250mm Gauss Cannon also prompted Yuri to ask his technicians to code a minimum range for the cannon in this vehicle's board computer. Another downside Yuri noticed is that the magnets this cannon uses will affect all nearby vehicles negatively, making usage combined with other vehicles a serious liability. However, the very same magnets could force EMP mines to explode when this vehicle comes nearby.
Yuri thought a lot about implementing much needed AA weapons with the Railgun, but a few tests proved that idea futile as those weapons had a tendency to malfunction with those powerful magnets close, and no matter the engine used, this vehicle could not afford the additional weight of additional protection against EMP and magnetism related effects.
The engine was the a stable multi-fuel engine which could provide a lot of power to propel this vehicle forwards without suffering much from the magnets. However, not even the best engine could prevent this vehicle from being amongst the slowest in recent history.
The armor is standard heavy perforated demagnitized steel armor, which is very resistant against all forms of ballistic weaponry and also prevents the vehicle from being affected by its own magnets.
When Yuri had to decide upon a name, he decided to call it after the greatest nightmare of the allies he had to eventually become his opponents; a return of the Tsar's family, and called it the Tsar Cannon. It quickly lived up its name, being extremely powerful and fearsome... but also expensive enough to only allow commanders which have proved themselves access to them.
Edited by Aasgier, 29 September 2012 - 08:20 AM.