Here's all you need: Tap is 6-48, and drill is supposed to be a #31, but I used a slightly smaller #33. I like the 'straight-flute' carbide ones. (...the 'guide' I have says use #33 for a 6-48 but #31 for a 6-40...?). I got Tap Magic at the Ace Hardware in town. A good center-punch is a must, and drill press.
Here's the specific parts I ordered from MidwayUSA:
- Drill Bit - $20.99 http://www.midwayusa.com/viewproduct/?p ... ber=669712
Tap - $2.29 http://www.midwayusa.com/viewProduct/?p ... ber=353742
Handle - $4.49 http://www.midwayusa.com/viewProduct/?p ... ber=330820
The sight needs to be far enough rearward that the case will eject; a bit behind the boltface's rearmost travel seems to work fine. If you haven't deactivated the semi-safety, you shouldn't cover it up.
Drill the first hole.
Then TAP the first hole. I like using a piece of rod or bolt that fits in the top end of the tap handle, and have the drill press 'guide' (no pressure downward) the tap as I turn it by hand, backing up a partial turn for every turn or so clockwise. Use lots of Tap Magic; it does seem to make a difference vs. 'WD-40'. I tap clear through and when the tap turns very easily you're done and can raise the chuck and back the tap out.
Countersink the holes very slightly or otherwise de-burr them.
Mount the sight with the first screw, and level it front to back before center-punching the second hole. Ideally your punch should be 'snug' enough in the sight's hole to be centered; 'eyeballing' it is too tricky. Some folks use a smaller drill bit just fitting the sight hole, or they will slip a very small bit inside a 'bearing' sleeve of tubing that fits the sight hole, and use the drill to 'mark' the second hole and start it at the same time.
Drill the Second hole, then tap it as above.
Both holes drilled now.
Put it all back together. (You might want NKJ's DVD for this part...)
Oh yeah - last step. . . Go shootin'. . . !!!