I inlet my action in the correct location in the blank and using a point made with the right sized bolt sharpened make a mark the wood with the action . I then mark the other end of the blank where I want the bolt hole to start. I then put a sharpened piece of rod in my 4 way drill press vise and the right sized bit in the drill press vise. I use a foresner bit for the bigdiameter hole because they are very stiff and don't wander. When I get to the right depth I switch drill bits using the point mark left by the forsner bit as my starting point and drill till I meet the action side starting point. This takes a lot of adjusting for depth on the drill press.

bill