I'm glad this thread was started. I'm fixing to attempt this same procedure using the same mount. This is the plan I have come up with. According to the instructions the mount is to be located 1.5 inches from the rear of the receiver and at a height so that removal of the top cover is possible. After locating these points and marking them on the receiver , I will remove the top cover and clamp the mount in place. The best way to make sure that the mount is level with the bore axis ,that I can think of , is to insert a range rod or indicator rod into the muzzle and place a level on this rod. Then level the receiver off of this. Once the rod and receiver are level I can then level the mount,making sure that I'm at or above the mark made earlier when determining top cover clearance. At this point the bore axis and the scope mount should be level with each other. With the mount clamped to the receiver I will then use a transfer punch of the correct size and center punch the holes. A center drill will then be used to start the holes on my drill press while using the mount as a template. The through holes will be drilled by starting with a smaller bit and increasing in size until desired dia. is achieved. The holes will be tapped using the drill press by inserting the tap in the chuck and turning by hand . Cutting fluid will be used generously for drilling and tapping. Also when tapping , turn the tap .25 to .5 turn and then turn back .
This may not be the correct way to do this operation but it is the best solution I have come up with.
PS I'm not a gunsmith.
The
HOG