A bullet compressing device for creating marks imparted by a barrel of a gun on a bullet, has: a first member; a second member spaced from the first member by a gap, a dimension of the gap selected to correspond to at least a length of the bullet, the first and second members slidingly receivable within the barrel of the gun; a biasing member in engagement with the first and second members, the biasing member having a compressed configuration in which the first and second members are biased toward one another thereby decreasing the dimension of the gap, one of the first and second members engageable by an actuator, the first and second members and the bullet received therebetween movable relative to the barrel thereby imparting marks on the bullet by the barrel upon actuation of the actuator.