The safety system of your gun uses the older system where a sickle shaped post connects the cross pin in the postthat goes through the slots in the trigger. A plate that slides along the bottom of the top tang that aligns the post with holes in the top strap. When it works right the safety button ( connected to the internal plate) aligns the post so that when the triggers are pulled the post enters the top strap hole far enough that the trigger blade moves up enough to push up the sear tails and trip the hammer. This is a 3 position safety. There is a coil spring around the top of the sickle post that holds the slide plate up and the cross pin down to push the cross pin onto the bottom of the slot in the triggers. Hope my explanation isn't as clear as mud! The length of the back screw and how tight it is can effect the operation of this system. Good luck and let me know if I can help.