The guns are 3D modeled into the main dat of the aircraft.
The sim controls those so shell settings and such mock say a .50 cal or whatever said craft carried in real life.
How accurate those settings are is probably based on who edited the settings for any given mod.
I don't make this stuff up. It's just the way the files work as they are.
One COULD do the aircraft guns like Ships are where the eqp assigns the guns.
But that would require a lot of work to remove the 3D model and replace with a node.
Then all the work to change an arse load of other stuff.
The upside would be changeable weapons based on dates and such.