Hold down "n" while shooting, all guns will train on the target and fire.
Uhhhhhhhhhhhhh, no.
When you jump to any gun, by pressing 2 thru the number of gunner positions on a particular aircraft, the number corresponding to each gunner position will display in the upper right of your screen.
Keyboard N or a joystick button set to Fire Primary
and Secondary will fire all guns on the bomber formation that will bear on the target you are aiming at.
As someone else stated, the "streams cross", converge, at 500 yards.
You can also have one person join you to gun for you but they only fire the single gun they are manning.
wrongway