How shall I break it to you, gently...
Once gunners have hit the caps (first acc, then reload), a 9/9 gunner is as good as yours.
A better gunner than yours would have better repair.
You also might want to consider burning experts, not for gaining more vets, but in order to have rookies that you can take off to save weight. Take off as many as you can until you are at the reload cap.
:)