A friend of mine went through a similar incident. But that was a state felony. That meant he had to go to the court he was tried in and ask for a certificate of relief from disabilities. But federal charge is altogether different. I take it you went across state lines so that is federal jurisdiction then not state. Ranwin is right about that get a lawyer better yet if you are a member of the NRA they have a list of lawyers that specifically deal with gun rights cases. The list is available to all members. Simply call their member hotline and they will find you a lawyer closest to you that they recommend. Make sure you tell them it was a federal charge.
"The deerskin rug on our study floor, the buck's head over the fireplace, what are these after all but the keys which have unlocked enchanted doors, and granted us not only health and vigor, but a fresh and fairer vision of existence" -Paul. Brandreth