Check your state and local firearms laws. If you are fortunate enough to live in a free state, you have no obligation (and in many cases no ability) to register anything. Now on the other hand if you live in a Communist country like CA, MA, NY, CT, exc., you are "supposed" to register according to dear leaders guidelines. Hope that answers your question.
Unfortunately for the subjects of these foreign countries, failure to register firearms when told to by dear leader can result in being charged with a felony.