Worse than poor machining - DoubleStar Ambi-Safety Selector for M16

I bought this selector for "correct" appearance on an M4A1 clone. The detent snaps positively into place at the stops on this selector, but it feels and sounds like there's gravel in it when moving between the stops. Upon closer inspection, the groove that the detent rides in looks like it was gnawed out with a dull butter knife. There are pits and ridges that are never going "break in" and allow smooth operation. Since I'm past the return date and out $23, I'll have to try to smooth it out with a die grinder. Or throw it away. I should have paid attention to the previous reviews and not bought this junk.