I am trying to take off my Gold Cup Trophy's rear sights, pretty simple right? For some reason I am having a really hard time removing the hex screw that attaches it to the slide. I have tried quite a few different size allen keys but I can't seem to find the correct one. I am starting think I may have stripped it. Does anyone know what size it is? The sight is attached by the screw, right? If I did indeed strip it, do you think a gunsmith could remove?

