Err? Naval shell is no different from 'land shell' - assuming bore and caliber are identical.
Nope. Really now, rethink that statement yourself. A naval gun is not under the same restrictions of handling as land artillery, nor are its propellant charges. The shells are often larger, so are the charges. I should know, I have an expended 5"/54 cartridge casing I use for an umbrella holder, relic of my father's service in the USN. What does a 203mm projectile weigh on land? What does it weigh at sea? (Over a thousand pounds, if we're talking about a Mark 8 APC round.) There are significant differences, you just don't choose to see them.
You better try to rethink that... After brief google search...
OTO melara has muzzle velocity of below 1000 mps.. Projectile weight is around 6.5 kg. Neither of which are in any way special or exceedingly high. So something like 'naval gun firing naval shells' does not explain that at all. More likely explanation is that T-55 is outdated tank with obsolete armor for MBT.
Sure it does. First, realize that a naval gun is designed to be extremely accurate against much more difficult targets than a tank; aircraft and even other ships are much faster and more manuverable. Then realize that the OTO is also capable of this degree of accuracy while firing in a fully automatic mode. T-72s died to this as well. We're not talking about them hitting and killing with one round each, but closer to 10 or 20 in rapid succession.