You can but without recutting the rear serrations they won't match. The rear serrations are cast into the slide. The finish is then ground and then yours was blackened. The metal just a few thousandths below the surface is still shiny colored and not blackened. Well, it shouldn't be. You'd have to get them cut in the front, recut to match in the back and then retreat the slide to finish the visual look of the slide.
Josh