I would take a look at the TSubclassOf template again. What you are getting in you Blueprints is actually a UClass object if I am not mistaken. To access the properties, I would suggest spawning an instance of the object first. This is similar to how the examples spawn a projectile from a TSubclassOf object in the shooter examples. Long story short your Primary Weapon get is returning a UClass object, not an AWeapon object, hence no access to the properties.
More on TSubclassOf: https://docs.unrealengine.com/latest/INT/API/Runtime/CoreUObject/UObject/TSubclassOf/index.html
More on spawning an object from TSubclassOf objects: A new, community-hosted Unreal Engine Wiki - Announcements - Unreal Engine Forums