Restoration of firearm rights varies a bit from state to state. In some states, it requires that the subject successfully complete the sentence. The person then files a request with the convicting court to not just have the record sealed/expunged, but to have the conviction vacated (it does mean treating it as if it never happened). In other places, after successfully completing the sentence, the person applies for sealing and expunging, then files a motion specifically requesting a restoration of firearm rights. In either case, that information then has to be sent to the feds so that the background check for purchases wlll reflect this.
What is interesting is that in some places, like Ohio, not all felony convictions create a "disability" preventing ownership or possession of a firearm. And, there are some misdemeanor offenses which do. And a misdemeanor Domestic Violence conviction is still a 2A killer.