In drilling the tang screw hole in the stock, you can come surprisingly close by drilling about halfway through  from the top and the bottom while “eyeballing” for correct alignment. It helps to have a helper check for alignment in one plane while you look in the other plane. It is best to first use an undersize bit, then drill completely through using the correct diameter bit, thereby correcting for initial misalignment.

The preferred and most accurate method is to use a drill press with a concentric center point located directly under the point of the drill bit. Some drill presses have a hole in the center of the table into which a center point can be placed, although there is no guarantee that the hole if accurately aligned. By attaching a piece of wood to the table – a piece of 3/4” plywood or a section of 1x4 or 1x6 – an accurately-aligned hole can be drilled into the piece of wood using a bit of the same diameter as the center point. A center point can be something as simply a a section of 1/4” wooden dowel which has be turned to a sharp point by chucking the dowel into the drill press and using a file and sandpaper to form the point. By placing the center point into the hole in the piece of wood on the table, you will have a point which is exactly under the point of the drill bit.

Once the stock is properly fit to the receiver, and after selecting a drill bit which will just pass through the upper receiver tang screw hole, with the stock installed on the receiver, set the lower tang screw hole on the drill press center point, then drill through from the top, using the upper tang screw hole as a guide for the drill bit. This will result is a very accurately-aligned tang screw hole. Be careful not to drill too far, thereby drilling into the lower receiver tang. It is best to stop slightly short and to complete the drilling of the tang screw hole with the stock off of the rifle.