If all you're gonna' do is "lap" the bolt face without doing the work on a lathe all you will be doing is polishing it, you won't know for sure that it is a true 90 deg. to the center line. Just 'truing" the bolt face on any 'factory' action probably won't show you a speck of increase in accuracy that you can make use of. A "target" action, like a Kelby, Bat, Hall or Stiller Cobra won't need the bolt face "trued,, because they already are! You're trying to pick out one little thing that will be the magic ticket to accuracy. The one thing I have found over the years is to specify a "tight neck" on the chambering reamer. SAMMI specs are very generous. As you are going to install the barrel yourself, I suspect we are taking about a pre threaded/chambered/crowned barrel for a Savage, and if that's the case, save your money, you won't see a measurable increase in accuracy.