first of.... go into play, and when you see bullet spawning, hit pause. then click on that bullet, hit resume and check its movement FSM.
and pay attention if it will go from movement state into self destruct state.
im suspecting it wont, so here is ur problem, with colliders.
report back with ur problem, and how colliders are set up on bullets, and rigidbodies and on enemy too
most of times, its problems with colliders, they need rigidbody 2d on it most of times, or collision detection settings changed