I have the same issue with my 870 with an IC choke. I am hitting 5-6 inches low at 40 yards. I called Williams yesterday to see what I could do and they are sending me a taller rear sight , free of charge. The have great customer service. I spent nearly 30 minutes BSing with the technician that helped about turkey hunting, hog hunting and bass fishing! Hopefully this solves my issue since these are very well built sights. I have literally had every model of Tru-Glo sights and they ALWAYS break!