[thatguy96]

There are actually only two classes that are really used for these, Class 4 and Class 5. One of the major differences being that one is a Flak/AA class, which allows it to op-fire at aircraft, while those classed as the other will not. I'm not sure if the restriction also exists for regular engagements. Also, the other class (used for Bow and Coax) has some other things in the code, that IIRC, prevents the weapon from being fired unless the vehicle is pointing at it when placed in the fourth slot (one of the reasons you'll sometimes see units with gaps or no weapons except in the fourth slot, especially turretless WWII tankettes).