Abstract: A locking device to be secured in a weapon, comprising a first locking means manoeuvrable by a lock cylinder (56), which locking means has a friction body (10) displaceably arranged in relation to the lock body (3-5) and insertable into the chamber or barrel of the weapon, and blocking elements (23) arranged to be moved into engagement with the inside wall of the chamber/barrel in case of mutual displacement between the friction body (10) and the lock body (3-5). The locking device furthermore comprising a second locking means (73), which by means of the lock cylinder (56) is movable into engagement with a space in the weapon located adjacent to the chamber/barrel in order to secure the locking device in the weapon.