I've found that enemy EXP AA guns either won't fire at my aircraft or don't track me properly. The range also isn't great, especially if the aircraft has bombs, because they can just hang above the tech and destroy it without the target being able to do anything to defend itself. I think that the AA gun should have an 'infinite' range like the megaton, but get slower and less accurate the further the shell goes. Maybe also add a proximity detonation to make them more formidable.