Calling it a gun wouldn't be powergaming, as long as you stick to it. If you expect people to believe and go along with your story of it being a walkingstick, you basically agree between you and them it's not a gun. Visually it ofcourse is, so it is purely roleplay that is agreed between you and the other person. If you then shoot that person in the same situation or use it in the same area of that person, I would say it is powergaming, since you basically denied them the chance to disarm you before and you agreed between the two of you it is not a gun.