Originally Posted by linde

John & Mike are very correct . . . the strain screw (that applies tension to the mainspring) is fitted to each individual gun at the factory to attain the correct tension setting. Fitting involves grinding the tip to the correct length so that the screw can (and should) be left tightened during normal operation.

There was . . . back in the day of serious bullseye shooters . . . a modification to the grip frame that added a set-screw and plunger . . . allowing fine tuning the strain screw during a match. Not intended for the casual shooter. See posts 7 and later in this thread.
Odd vertical hole in some vintage California custom grips

Unfortunately Photobucket blocked many critical pictures but I've attached the one from post #9 that tells . . . the rest of the story.

Russ