Re: Change in horizontal zero when dialing in??
Reticle out of plumb can certianly cause this, but with any light weight firearm recoil can cause this too, espcially a pistol. None of use are mechanical vises and we all allow the rifle to recoil. How the rifle is fitted to our shoulder, or in your case the way you grip the pistol is going to effect the way the gun moves due to recoil. How strong your hand and wrist are, how your elbow is flexed, the weight of your arm all are mechanical elements that can be adjusted to help work this out. I'm not a pistol coach so I won't try to tell you what and how to change, but this is a lesson that I learned growing up left handed in a RH family. Every rifle was sighted in by a RH shooter whose body would twist to the right due to recoil. When the lefty shot the shoulder would rotate the opposite direction and I would always have a different zero than anybody else. This was even more pronounced in shooting a pistol comparing heavy bullets hitting higher than lighter bullets. Everything in the charts says this should be the opposite. But the charts are only considering the bullets flight out of a non-moving barrel. In the real world the heavy bullets were slower getting started, stayed in the barrel longer and were aimed higher due to my pistol beginning to rise due to the recoil.
Sorry I can't give you an exact answer, but maybe knowing where to look will help you find your answer.
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