The name isnt hard and fast, and I prefer the name Tarantula because its more unique than Scorpion which has been applied to countless vechiles and weapons systems. I'm not even really sure why I called this version Scorpion because thinking about it there was no reason too...the tank even resembles a Tarantula more than a Scorpion...yeah recon I'll change it back.
As for the short barrel I just wanted something that looked a bit diffrent and that fitted with the swept back shape of the tank, a longer barrel would've ruined in the look in my opinion. Intresting that shortened barrels make for reduced recoil. The approximate concept behind the weapon (science aside) was that it would be a two stage munition, primarily a projectile which would pierce the targets armour, and secondly an energy beam that would inflict the real damage to the interior and crew. The tank would have to remain aimed at the same spot for a longer length of time than with a more conventional gun, so maybe I'll tie that reduced recoil aspect into it 
All these tanks are essentially designed for an urban combat mod, and so are either dedicated to or variants suited for urban combat with the accompanying short ranges. Being able to engage a target a kilometre away wouldnt be essential either from a gaming or background point of view.
All your comments have been great so far guys, I'm not sure you realise how much this is helping me. besides the technical and drawing information its really intresting to hear peoples reactions.