I use a forsner bit for the large hole with extensions as the hole deepens and a brad point bit from the action side. I set my drill press up with a point in the 4 way vise and make sure it is in perfect alignment with the machine head. Put the point on where you are going and know where you are starting from. Be careful on the web you leave between the action and large diameter hole. If you make it to thin the through bolt will interfere with the inertial block and the gun won't function. I also try to use a few Bellville washers behind the bolt head to compensate for any crush of the wood during use.
bill
