Does the “Clean Slate” restore Second Amendment Constitutional rights? I didn’t think so.
Once a conviction has been set aside by the state, the individual will not legally be considered to have been previously convicted of that crime. However, a conviction that is set aside can still be considered a “prior conviction” by courts, law enforcement agencies and attorneys for the purpose of charging an individual with a second or subsequent offense.
Since the ATF has been prohibited from expending funds to restore Second Amendment rights to ex-felons, and I don't think the "Clean Slate" bill removes an individual's felony conviction from the FBI database, I'm not sure if an 'expungement' can be appealed to the NICS system.