As you said you are restoring a Mk I, A original Mark I bolt would probably not have had such a roughly finished bolt. I would look for a better looking bolt. I say

---------- Post added at 09:51 AM ---------- Previous post was at 09:47 AM ----------

I slipped up and posted a tad early - Sorry. I would have the Head Space of your Mark I checked when you change bolts if you are considering shooting it.