The present invention relates to a locking element to be inserted into the barrel and/or the cartridge chamber of a firearm, said locking element comprising: a sleeve with an actuator, an operating element and a wedge element provided therein, wherein the operating element is at least partially provided movably within the wedge element. The actuator can insert the operating element into the wedge element which causes the wedge element to expand and be pressed against the wall of the barrel thus blocking the barrel. The actuator can also move the operating element out of the wedge element so that the wedge element can move back into a position in which the locking element can be removed from the barrel wherein the actuator is operated via an electronic device located in the locking device or a separate operating unit.