1) Wipe paste wax or shoe polish on swivel screw threads, being careful not to fill the thread grooves.
2) Break a toothpick into a few pieces.
3) Mix up two drops of epoxy.
4) Smear epoxy on pieces, and put remainder into hole.
5) Place pieces around the outer edge of the hole in the stock.
6) Turn the sling screw, on which the wax has now dried, back into the hole.
7) After a few hours, before the epoxy bis fully cured, turn the screw out, lightly wax it again and turn it back into the stock.
Have done quite a few over the years, and never had one pull out.
Ted