if your hitting low slide your rear sight UP.

also keep in mind that some guns dont fit some ppl correctly w/ iron sights. you should be able to close your eyes, mount your gun and have the sights pop uyp perfectly when you open your eyes. soooo by drastic movements w/ the rear sight it might not be set up right for you depending on your size, how you hold it and the drop of comb. so in some instances ive seen the hight of the front ramp need to be changed.....but for what your asking, you need to go up w/ the rear. sorry if i made that a little confusing for ya