I just recieved my NECG ghost ring rear sight (from Brownells). I decided to go this way rather than a taller front sight because of the adjustability. I've put it on and it should give me 200mm of correction which will almost be POA with the 400gn projys. I could file some metal off the bottom of the aperature post to allow it to screw in further - it has the thread but contacts the receiver first.