Looking down the sight on the windage side there should be a small flat head screw. Not the big button head, the small shaft with a cut out in the center of the knob. Loosen it, and you should feel a clunk in the sight, it's stepped on increments . Keep loosening it until you have free but tight adjustment. You might want to tighten that little guy back down once you zero.
You can see a 7th round mod in this picture. The area that would get nicked would be built up with a weld and then reworked.
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Update ...The gun is more accurate than I am. I need to stretch out to 100 yards next trip and rock on.