A new Sicaran tank is available today wielding a massive Punisher Rotary Cannon that is S5 with 18 shots.
Legion Sicaran Punisher Assault Tank £79
The 8th Edition Rules for this tank are in Forgeworld's Imperial Armour - Index Forces of the Adeptus Astartes, and available as a download for the Horus Heresy
Here are the experimental rules for the Horus Heresy
and for those wanting to see this thing for 8th Edition......