I guess “basically” means “not exactly”, right? 
. Can you show me the code of that class? Or the changes made to it, if it’s a changed gun class and not a new one derived from it.
My first thought is that Firearm does not correctly inherit from the classes it’s supposed to inherit from. The original Gun class inherits from pickableObject. Maybe you’ve made some changes to that class and removed correct inheritance by accident?
Anyhow, please show the code for Firearm.