Use Black silicone

Talented "old school" master gunsmiths make their own screws and pins when necessary.

I just watched one being made about a week ago for a missing screw on a barrel sling swivel on an imported German sxs. Pretty cool. Removed and measured the remaining set screw in barrel swivel fixture for head size, length, diameter and thread pitch. Chucked up some round metal rod in in a lathe and turned it down to thread diameter, leaving a head. Constant measurements by caliper. Cut off for length and shape head with file and sandpaper. Cut a screwdriver slot in head with fine file. Tap and die set used to make the metric threads and cut hole to accept them. Touch of Oxpho Blue on that polished slotted screw head once done. Voila. Installed into sling swivel fixture on lower rib. New screw indistinguishable from the original remaining screw. Took maybe 20 to 25 minutes.

If I wanted the sling swivel fixture removed completely he would have made two threaded studs to fill the old screw holes in the bottom rib. One threaded stud like that would fill an empty bead sight.

I have heard of smiths making metal parts like this but I had never seen it done in person until last week. Pretty damn cool.