A2 Iron Sight problem

[esaabye]

So I went out today to get ready for the Appleseed shoot next weekend. The shoot is designed to work on marksmanship with iron sight so I pulled the scopes off and went to the south range.

I went thru the 25 meter zero with my Bushmater A2 and ended up way from the "Mechanical Zero". I included a picture of the windage setting when all was done, I am at least 6 clicks left of center.

So the question is, what is up with this and how can I or should I correct this? Seems to me the front site must be off but???

This is my first AR so any help would be welcomed.

Thanks!