Sounds like your gun is a canidate for the wax treatment. This is a little known techinque we armours use from time to time to cure hidden problems we see before the owner can complain bout it. Well, yes it does sound strange but by golly it works!
First say we'd dip ya slide in melted candlewax. This creates a good base for the bees wax application that follows. We allow the wax to harden and then we freeze it for about two hours. This allows for the molecular structure of the metal to re-align from the dip treatment.
Now, fresh out of the freezer, we torch the wax off (mostly) and then use a sooting effect to cover the metal briefly while everyting is still warm. Back to the vats and a good dip into some beeswax for about ten minutes. Once removed, it isn't allowed to dry but wiped down with a terracloth rag.
To get all this completed, we hang the slide in an oven and bake the remaining waxes and soot into the finish for about an hour fifteen minutes.
Cool it down in a quick dip in icewater ( I heard some smiths down south use their sweet tea) and reassemble.
NOT TO BE DONE on any plastic parts mind you!
Buddy, if that gun squeaks after a treatment of that. We start the Jack Daniels approach.