I am  starting  the  build of  a flat-top carbine.  I will be using some  sort of  optical sight  like  EOtech or Aimpoint  but I  want to  have back up iron sights as well.  I also  would like to retain the standard AR15 front sight   rather than going to  one of those folding  sights. I would also  prefer to use  a  non folding  clamp on sight similar to the  regular A2  rear  sight.  So the question  then becomes  what  type of  rail setup   would work best and  what would be the  best  rear sight to use.
Obviously pinpoint accuracy is not an issue  here as long as we can  get it on the papaer at 100 yards  

After reading many positive reviews I bought the LMT BUIS. It's exactly what I was looking for to keep my carbine light and accurate. Check it out.