Abstract: A locking device for guns, comprising a cylindrical locking pin housed in a housing cavity made in a suitable part of the revolver, having one operable head portion apparent on the external surface of the revolver and an opposite end portion, and a substantially helicoidal groove cooperating with a retention pin, the device locking the revolver when, upon operation with a suitable key, the said locking pin translates inside its housing cavity projecting one of its ends outwards the said housing cavity in order to cooperate with the striking surface so that the said projected end obstructs hammer cocking movement.