thanks to all who have posted, I am going to order the HiViz sights soon and try to mod my sigma. All your posts have helped me in dialing in my gun. Out of the box at 15 yards it was shooting 8 inches low and about 6 inches right. I thought ther was no adjustment to be made in the rear sight being "fixed" and have have through countless rounds trying to figure out what I was doing wrong.