The screw only adjusts over-travel. It screws into a plunger which contacts the underside of the receiver, with the over-travel spring sitting over the plunger. the spring only supplies force to return the trigger (black) against the sear bar, which has its own spring under the silver colored dome.
I took the trigger assembly apart tonight and saw some grit and burrs on some contact surfaces. Used 320 Grit Clover Compound on some wood to clean up the surfaces. Pull is still on the heavy side , but a lot smoother.