Abstract: A firearm lock that utilizes two separable parts. When locked in place they fully occupy a gun's barrel and chamber. One part, a dummy round, has a tubular forward area with a recessed inner groove proportioned to accept the second part so that the two can be locked together. The other part uses a tubular bore bar permanently attached to an adapted lock with an actuating rod located through the length of both to provide a way of locking and unlocking the device. A plurality of slots are cut in the bore bar's inner end so as to create a series of flexible tines. When in the locked position, the actuating rod extends through the bore bar's inner end, and the tines cannot move. When unlocked, the actuating rod can move to provide room for the tines to flex so that insertion and withdrawal from the dummy round can be accomplished. The locking and unlocking of the device is achieved by restricting the axially movement of the actuating rod with a lock engaging portion located inside the adapted lock.