No, as a general rule, Kydex holsters will not scratch your gun. Kydex is a type of plastic, which is, of course, a softer material than the metal components of your gun. Some guns are built with lots of polymer parts, like Glocks, both materials are relatively soft and shouldn’t damage one another. So as long as you aren’t purposely jamming your gun haphazardly into your holster, you shouldn’t see any scratching from the Kydex. Like all holsters, though, after repeated holstering and unholstering, your gun will exhibit wear marks from use—but that’s different than Kydex scratching a gun.