In all seriousness, how did single action pistols come up in the conversation? The PF9 is DAO.
A pistol that fires only in "double action mode" is technically a single action as it has only a single mode. The term "double action" came into being because a pistol that can be hammer cocked and cocked by the trigger has two action modes, thus "double action." The sense in which dross used the term is the commonly used, but technically incorrect, understanding. It sounds as if the witness was using the term to confuse the jury.