Note: For those interested in what the Hydra Flak Tank is armed with.
It is armed with 2 twin-linked autocannons.
Autocannons are similar in concept to twentieth century tank guns. They are rapid firing and use mass-reactive explosive ammunition.
That would be the Eradicator or Executioner variants.
Though the Eradicator variant fires heavy, high-calibre shells can flatten both enemy barricades and any infantry sheltering behind.
Whereas the Executioner fires plasma as a glowing super-heated bolt of energy, which on hitting an object, react with its matter to produce spheres of boiling nuclear energy like miniature suns.