There are a few tools that you really need to get it right . if you have them I am sure you know what I am talking about.
if you have a shouldered center punch and know how to clamp the scope mount you can use it for the pattern[make sure the shoulder is the same size as the hole in the mount so it centers exactly. You have to have a set of numbered drills and a depth gage for them [you would not believe how many people ruin barrels by drilling through]
You must have a special tap for blind holes that will cut threads all the way to the bottom of the hole and know how to use it.
If you don't have the right tools and know how to use them you really are better off taking it to a gunsmith. Lee