I have seen Savage bolts that are parkerized, you would do this after bead blasting it. Probably would want a fairly fine finish on it however. I think you would be unhappy with one of the coatings/paints on a bolt. There are lots of sliding actions going on, I doubt you will cycle it too many times before it chips some place, like where the front baffel rotates or the pin goes through to hold the bolt head on. If you want it dark, near black then parkerizing will make a much more durable finish. If you do this however, do not use aluminum oxide to blast it with, tiny particles will be stuck on the surface which will screw up the parkerising finish, best to use plain fine sand. I have done dozens of barrels this way and it makes a very nice finish. Larry