Drill a new hole to replace the one you cut off. You can use the 4mm x 0.7 screw supplied with the sight, if you drill it for that one.
Mark the breech for the sight base screw hole. I used another screw in the backside of the breech to hold the sight in place and
then center punched where I wanted to drill.
Drill the hole in the breech according to the screw size and thread pitch you want to use.
Tap the breech using cutting fluid and try to get it started straight.
I used an old 10-32 shouldered screw for the project. It needs to be turned down so 0.610 of 8-32 threads can be used on one side
and 0.360 of 4mm x 0.7 threads on the other. The rest needs to be left larger to hold the breech on. You could also make the sight base
shorter and use a stud in the rear hole for elevation adjustment. Lots of ways to do this.
The sight base needs to be bent upward just in front of the mounting screw for the sight elevation knob to index properly. It is
spring steel so a bit hard to bend but a vise and crescent wrench will get the job done. I put a small rubber o-ring down the front sight
screw hole before installing the sight. It holds the bolt open when you are loading with the gun pointed down.
Note from Fireball, This segment was taken,
with permission from Bio's original post. some sections were edited to fit with
the "How To" nature of the Tech! section.
