It also matter on what you want the battleship to do.
Anti ''little things'' ?
Anti Cap?
Or mixed up ?
Anti small, would have some some differences with each other, normally you'd have alot of solarises and some razors if you can aim, but if you're better, secondaries can work just as well, well, almost as well.
Anti cap...load it with primaries, HM, a missile or 2 to take care of smaller caps that tend to thrust away from you, Edit: Forgot, some 2-3 pulses would work better for other BS's shields
Mixed up...well..secondaries and primaries, it makes a sort of chain fire, maybe some 3 solaris or something, I dunno, 'mixed up' is hard to actually set-up effectively, as it's mostly based on your skill.
But, for the main part I don't know, you'd have to set-up what you feel good about, although asking some tips from REAL battleship whores could word :D
Two pulse cannons and the rest all Liberty primaries.
If you know how to dodge and strafe well, there will be no hope to hit you even within two kilometers, even one kilometer is too much. For me at least.