In The Dark Tower VI: Song of Susannah towards the end of the book Jake and Pere Callahan go under the WTC to put Black 13 in a long-term storage locker. It is mentioned that the Orizas Jake is carrying do not set off the metal detector they have to pass through. However, it doesn't mention that the Ruger Callahan is packing (lent to him by Jake) doesn't set it off as well.
How could a Ruger make it through the metal detector? It seemed odd to me that they specifically mention the Orizas which brought up in my mind their companion weapon, the Ruger.