how do you shoot from the rear gunner position?

[manintrees]

Whenever I am in a plane with a rear gunner I cannot figure out how to shoot. I set the view and I can see the targeting recticule but what button do I press to shoot?

Also, I was in a campaign mission the other day (realistic) and everytime I used the hat switch it would automatically switch to cockpit view when I released the switch. Has anyone else experienced this?