The galling concern with the 659 and obsession with special lubrication is really overblown. Surfaces tend to polish smooth with modern gun steel not gall. A little oil now and then and you are good to go. Too much oil or grease makes a mess and because it attracts dirt makes a gun less reliable. The rails ae just guiding the slide from flying off the frame. It would not be unusual for there to be some rattle between the two and the most force is taken up by the recoil spring and surface of the frame that stops the barrel. Also the locking surfaces on the smith and wesson 3rd generation guns could theoretically gall against the frame but again I think the amount of pressure between the two surfaces is minimal. Wear is normal.