Query About Reticles And Point Of Aim


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RaymondMillbrae
June 13, 2007, 11:45 PM
Hey Folks,

I'm back again with yet another question. This time it's in regards to reticles and point of aim. Let me try to make my query understandable.

My buddy and me were speaking the other day and the topic came up: Why does the point of aim change when you have the crosshairs on a target using high power magnification - but when you go to low power magnification (while still having the target in your crosshairs) you will not be centered?

Did that make sense to yall?

In other words, I have always understood that if I zeroed my crosshairs on a target using high power magnification, that I must always place it back in full magnification prior to shooting...for precision. But if the truth be told, I never really understood why this was.

If someone could shed some technical light on this topic - IN AN INTELLIGABLE WAY - I'd appreciate it.

Thanks.

In Christ: Raymond

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jlmurphy
June 14, 2007, 01:14 AM
In theory the reticle should still be centered regardless of the magnification. That being said, poorly made scopes might experience that problem, that is one reason most target shooters don't change magnification in the middle of a group, and many benchrest scopes are fixed power.

aspade
June 14, 2007, 01:15 AM
I can think of three explanations, in ascending order of complexity.

1. Gun is not secured to the bench and the torque of twisting the magnification ring is moving it slightly

2. POS scope.

3. Parallax issue. Parallax is a reticle focus issue where the crosshairs will move over the image depending on the position of your eye. It is much more pronounced at higher magnification. If you have a consistent cheekweld you can get the crosshairs to overlay the same (wrong) place everytime and zero for that. Drop it down to 3X and the parallax shift essentially goes away, leaving you with a wrong zero.

Zak Smith
June 14, 2007, 02:57 AM
aspade nailed it. Zero drift due to magnification change is more common in cheap and very cheap scopes. It's generally not a problem in Leupold and anything more expensive. Parallax is also a possibility, and you can detect if this is it by moving your head keeping the gun still and see if the crosshairs appear to wiggle.

RaymondMillbrae
June 14, 2007, 07:40 PM
Thanks guys!

I want to do a bit more research on this "parallax topic" so that I can explain it to my buddy in an understandable way.

In Christ: Raymond

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