Remove the old sight. Open hole with a No. 29 drill. Next, enlarge with a tapered reamer. Be careful not to ream too deep. Press the sight in place by hand. Finally, drive the base level with rib using a piece of hardwood.

Install 12 to 14 inches from the muzzle using the same procedure as #10 but with a No. 47 drill.

Remove the old sight and drill out the hole using a No. 31 drill. Thread hole with a 6/48 tap and screw in the 10D sight using the special spanner wrench. On guns without rib where the end of the sleeve projects into the barrel, file off until flush with inner surface.