Can't fire rear weapon?

My ship is a Mola Ramsayi, I have a 2MW rapid-fire beam laser mounted to the front weapon and another one mounted to the rear weapon.

I assume to use the rear weapon I need to switch to reverse view (numpad 2), and hit space. When I'm in this view nothing happens. I do have a combat target locked. If I'm in any other view (forward, up, down, side) then the front laser fires.