A practice device for use with a gun includes a laser-producing mechanism for producing a laser beam simulating a fired-bullet pathway. The device includes a bore insert with a striker member which the firing pin of the gun impacts and moves during a firing movement thereof. The movement of the striker member moves an electrical switch mounted on the bore insert to form a closed electrical circuit to activate the laser-producing mechanism. The electrical switch automatically returns to an open-circuit position to turn the laser beam off. A support which preferably includes resilient plastic bristles extends radially outwardly from the bore insert to prevent damage to the gun bore inner surface and to allow for use with guns having different bore sizes. The laser-producing mechanism is pivotally mounted on the bore insert to provide alignment thereof.