Why does the reticle move when I change the magnification?

[Ledd Slinger]

You guys are killin' me! If the crosshairs are not perfectly optically centered in a second focal plane scope...of course the poi changes with magnification.


Think about it like this...If you have windage references on the crosshair, you can see it. Do those windage hash marks maintain their value across different magnification level? Of course not! Why, because they're not in the center. As the target changes size due to changing the magnification setting, the value changes. i.e., 1moa@20x = 2moa@10x.


Think about it!

Talking about elevation on CENTER of reticle here. Not windage hash marks.

Elevation compensation marks below center on a BDC reticle will do the same thing as you are describing with the windage marks. But the center of the reticle should not move with magnification changes.

 

[Ledd Slinger]

Here is another good point i found on another site while looking into this issue. Could be a possibility...

"Something that could be a factor:If the rings are not truly co-axial,there will be some tube distortion when the rings are tightened.

The scope may have been made very precisely,tolerances in the .0002 in range,but if you distort the tube .002 in,you may introduce variation in POA"

 

[Ledd Slinger]

Also found another person finding the same issue with a NightForce scope. (Discussing POA shift with magnification changes):

"I have definitely seen this with a $1500 Nightforce scope at my range. We even tried it on a different rifle with different rings and with different shooters. Full zoom at 100 yards was more than 3 MOA off than least zoom at 100 yards."

 

[Ledd Slinger]

Another reply on the subject where a manufacturer did in fact correct the issue. (Asking if POA shouldchange with magnification powers)...

"The short answer is no, it shouldn't. However, on some scopes it does. The manufacturer can make the scope so that there isn't a noticeable movement of POA. If I owned a higher end scope (I own several) and it was doing this, I'd be sending it back to the manufacturer. I had one scope do this about twenty years ago and sent it back. Got it back corrected."

 

[dkhunt14]

I thought the OP would get on here and tell the problem. He was using a lower hash mark. When turning the power it was moving the reticule like Gunsandgunsmithing and I said. I guess he was embarrassed to come on here and answer. He told me Saturday at the match. He then set the gun up and saw what happened. Matt

 

[sscoyote]

Jeez!

I've been checking all my scopes of late and the reticle axis moves several minutes along the boresighter grid when adjusting parallax mostly on a number of them. Fortunately it does it at the closer end of the adjustment than at the further, but some are 5 minutes or more of movement.

 

[sscoyote]

You guys are killin' me! If the crosshairs are not perfectly optically centered in a second focal plane scope...of course the poi changes with magnification.


Think about it like this...If you have windage references on the crosshair, you can see it. Do those windage hash marks maintain their value across different magnification level? Of course not! Why, because they're not in the center. As the target changes size due to changing the magnification setting, the value changes. i.e., 1moa@20x = 2moa@10x.


Think about it!

This may be kinda' funny here. G&G when i refer to reticle shift, i'm not talking about subtension change with magnification change. I'm talking about the entire reticle itself (or maybe the lens or reticle housing) moving and sometimes jumping several MOA as seen at the reticle axis mostly as parallax AS WELL AS power is changed when using a grid boresighter. Just wondering if you may have been referring to my post.

Actually glad you brought it up though as it made me think to stress this point to some shooters since many don't understand reticle subtension changes in 2nd FP optics, and they may think there's something wrong with the scope when the subtensions change with power changes. Have to remember to explain it myself...thanks for making me think...for a change.

 

[Ledd Slinger]

I thought the OP would get on here and tell the problem. He was using a lower hash mark. When turning the power it was moving the reticule like Gunsandgunsmithing and I said. I guess he was embarrassed to come on here and answer. He told me Saturday at the match. He then set the gun up and saw what happened. Matt

Oh. Thanks for the info. It all makes sense now

 

[gunsandgunsmithing]

After a little research, I'm embarrassed. I owe you all an apology! I was wrong and have got to say so.


Yes, using a different subtension will move poi with mag changes, but not the center one. Sorry for my confusion.

 

[Ledd Slinger]

After a little research, I'm embarrassed. I owe you all an apology! I was wrong and have got to say so.


Yes, using a different subtension will move poi with mag changes, but not the center one. Sorry for my confusion.

No big deal. At least you got it figured out and know that theres nothing wrong with your scope