I'm trying to change my night sights and I can't get the front night sight off. It's not the screw on type. I'm not sure how to get it off. I seem to have managed to loosen it a little trying to get it off with a punch from inside the slide, however; still can't get it off. Not sure how to get it off, it doesn't have a screw to unscrew on the inside like most do. I don't remember the brand but I think they are old Trijicons 10+ years old.