The problem is that while California may expunge the domestic violence matter, which would enable you to get your state gun
rights back in ten years (unless the court would grant it earlier), there is also a Federal ban against firearms for anyone convicted of a crime of domestic violence
Even if the offense you ended up pleading to was not a domestic violence offense, if according to 18 U.S.C. § 921(33)(a),
if your offense has as an element:
1) the use or attempted use of physical force, or the threatened use of a deadly weapon,
2) committed by a current or former spouse, parent, or guardian of the victim, by a person with whom the victim shares a child in common, by a person who is cohabiting with or has cohabited with the victim as a spouse, parent or guardian, or by a person similarly situated to a spouse, parent, or guardian of the victim.
your offense would be considered a crime of domestic violence.
So you would need to have your California gun rights specifically restored by the state, along with the expungement. Without that, short of a pardon from the President of the US, you would not be able to get your Federal gun rights back.