Alright, so I copied the item_kinds1 + textures/resources from one of the firearm mods for .96 to the module I am working on just to see if it works.
My character started out with a pistol+bullet, so I'm guessing that was because of the new item_kinds1. The pistol works so that was cool, but none of the shops carry any of the firearms. Considering this is from a mod that is based on firearm, with lots of different types I have come to the conclusion that the main reason for firearms not showing up in stores is hard coded into 1.003/native module.
Correct me if I'm wrong but until the new mod system comes out, no guns in mount and blade.