Those rear buckhorn sights come in 2 different heights.
It sounds like you have the high one, and you need to swap it out to match your front sight. Look in the Midway or Brownells web site at the Marbles sights to see what I am talking about. Then measure yours. You don't need a micrometer - the difference between the two is about 15/100", which you can measure with a carpenter's ruler.
