When I saw TFA, I think saw something I really hope I didn’t see. One of the trailers before TFA was for Batman vs. Superman. I think I saw Batman with a gun. I really, really, hope I am wrong about this.
You sure it wasn’t the gizmo he uses to fire grappling hooks? That changes design a lot from incarnation to incarnation? I think Batman has had a gun capable of firing a sliver of Kryptonite into Superman, just in case if he ever went rogue.
The Batmobile did have machine guns in the '89 film.