I have a mini 181 model, blue, purchased in 1979 -- adjustment of the rear sight for windage requires the sight to be moved almost to right edge of the receiver. The gun shoots to the left with the sight centered. Is this normal for such a large adjustment? I also have a 181, in stainless, purchased in 1982 and the rear sight for windage is centered on the receiver to hit point of aim. Just curious.