[Don H]

BATF has an answer for you:

Q: If an individual is changing his or her State of residence and the individual’s application to transport the NFA firearm cannot be approved because of a prohibition in the new State, what options does a lawful possessor have?
NFA firearms may be left in a safe deposit box in his or her former State of residence. Also, the firearm could be left or stored in the former State of residence at the house of a friend or relative in a locked room or container to which only the registered owner has a key. The friend or relative should be supplied with a copy of the registration forms and a letter from the owner authorizing storage of the firearm at that location.

http://www.atf.gov/firearms/faq/nati...ernate-storage