April 9th, 2015, 12:35
The boxes you see on the 5 inch gun muzzles are gmax Dummy objects. These are emitters in CFS3: they fix where the guns fire from and which direction they fire in, so the Dummy object's pivot must be correctly aligned. If the emitter's pivot Y axis points straight up, the gun will fire straight up, which would be really handy on a Bf109, duh. Depending on the name used, the gun may be fixed like the 109's cannon or trainable like a Lancaster's rear turret. The gun type fired is defined in the model's .xdp file.
You can see other emitters in the picture, they're used for locating and orientating effects which are defined in the .model's .xdp file: exhaust flames and smoke in this case:–