I just came here to bump this thread to get more attention for shock cannons. These are such beautiful weapons and fine as they are ... with the exception of having way too low of an ammo count. 300% of its current ammo cap would be a good start. Or make them deal absolute damage only. In any case, increase their total damage.
A standard C3 fixed multicannon has a total damage output of 3.925 * 2200 = 8635 dmg
An overcharged C3 fixed multicannon has a total damage output of 6.672 * 2200 = 14678.4
A C3 fixed shock cannon has a total damage output of 18.14 * 256 = 4643.84 dmg
So an overcharged C3 fixed multicannon has a 14678.4 / 4643.84 = 3.16 times higher total damage output than a C3 fixed shock cannon. Hence I suggest a 3 times increase in ammo. Alternatively, Finally allow us to engineer them. This way they could be balanced too.
But for the love of shock cannons do something.