Anthony Pettiti in San Lorenzo does really good work, though he tends to run in benchrest crowds. He advertises in Precision Shooting, and will do small jobs like brakes, or full on benchrest rigs.
Then there's Jerry Rice with NorCal Precision in American Canyon. I don't know if he does piece work, but I have a 6x284 of his that's way better than I am.
Neither in Sac area, but maybe American Canyon works?