I wouldn't worry too much about the terminology. How many watts is your gun? Typically a gun will have more "power" than an iron. Perhaps you need to use more flux or get a new tip for the gun?
If the tip is cruddy that will cause it to never really get hot enough. Clean the tip really well and try again.
The most frequent cause of lack of sufficient heat I remember with the old Weller guns was the two mounting connection nuts for the heating element would get loose due to normal heating/cooling cycles from normal use.