I purchased some aftermarket night sights for my non-laser SW M&P .380 Bodyguard. Changing the front sight was a two minute job with a brass punch, but the stock rear won't budge. Does anyone know if there is a set screw in this sight? It has a small circular textured center that resembles a cap, but it does not come out. I've tried a brass punch, a sight pusher, lots of oil and even put it in the freezer, but nothing wants to move (and I don't want to break it). Any help would be appreciated.