I recently bought a used SIG 229 in 9mm and the frame to slide fit seems a little loose. The accuaracy seems fine. Is this something to be concerned with or is it just another "if it ain't broke don't fix it?".
Slide to frame fit is a small part of the accuracy equation. Barrel quality and fit to the frame and slide is far more important as is a good trigger. I have a 1911-A1 that is a rattle trap, but it always feeds, goes bang and has good accuracy no matter how dirty it gets.