im using skinbox from chaoscode
send a tickets to K1lly0u
I would ask him if his mod changes the weapon ID when it applies a skin.
If it does then that is the issue as the Weaponry stat allows more ammo per clip but stores the data based on weapon ID. If that changes after a skin is applied and the weapon has already been loaded with extra ammo then it'll take the current ammo and readd the Weaponry stat to it as the ID of that weapon was lost.
So it's not either plugin messing up it's just a direct conflict between them that will have to be figured out. Possibly limiting the number of times a weapon can be reskinned or finding a way for it not to change the ID.
This is all assuming that's what is happening. I'll look through XPerience and make sure there isn't a problem with that stat but it was tested thoroughly before it was released to public.