What distance to zero in scope

I just did a little experimentation today. I shot one round at the same target starting at 10 yards, moving it back 10 yards between each shot out to 110 yards and I found that my first zero is more like 15 yards and the second zero is between 90 and 100. Oddly, as the P.O.I. rose above my P.O.A., it also drifted left until it peaked around 70yds and as it came back down, it also came back to the right. Almost like the vertical plane of the scope isn't parallel with the centerliline of the trajectory.
 
"danhor7"Oddly, as the P.O.I. rose above my P.O.A., it also drifted left until it peaked around 70yds and as it came back down, it also came back to the right. Almost like the vertical plane of the scope isn't parallel with the centerliline of the trajectory.
I have exactally the same problem and it's driving me crazy, trying to figure it out. I am dead on at 35 yds, but at 10 yds it's 1/2" to the left, and low of course, as expected. Anyone know what's going on?
 
This one is pretty simple guys, Your scope is not perfectly in line with your barrel. Sure you are zeroed in at "x" distance. But as you shoot farther you will be either more to the left or the right if your barrel and scope are not in line. Lets say you are zeroed at 40 yards, and you shoot 60 yards and your POI is to the right. I guarantee that you POI will be to the left if you shoot at 20 yards. Situation is the same vice versa.
That's why they sell windage adjustable mounts to correct this issue.

Cheers 
 
I remember reading an article on this very subject. The author recommended 20 yards for the first zero, for guns shooting around 800 fps. The gist of the article was this gave the flatest trajectory between the first zero and out to about 50 yards or so. I have attached an article from Pyramydair.com that explains it in more detail.
http://www.pyramydair.com/blog/2005/06/at-what-range-should-you-zero-your-scope/