# Does changing scope power effect POI?



## stillhunterman (Feb 15, 2009)

Hmm, have a curious question. Not big on shooting/bullet knowledge, but I know my gun well. Have been using new ammo over the summer since I cant find my federal premium accubonds. Been using the Winchester AB's and the Nosler AB's. My gun definately likes the feds much more but the Win's are shooting well. I did notice that when I changed my scope power from 4 to 9 my group seemed to 'move' a half inch or so at 200 yards, but kept close to the same grouping. Is it shooter error or is there something to changing power and point of impact?

Thanks for any insight. BTW, it's not a big deal, am shooting more than well enough to bring down a critter out to my comfort zone, just more curious than anything.


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## DallanC (Jan 13, 2009)

Yes, that is why some scopes have parallax adjustment knob. Doesn't matter so much for MOE (minute of elk) but the different in hitting a prairie dog or not at 600 is alot. Target model scopes almost always have some form of parallax adjustment (leupolds have it on some models on the end of the bell).

-DallanC


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## colorcountrygunner (Oct 6, 2009)

DallanC said:


> Yes, that is why some scopes have parallax adjustment knob. Doesn't matter so much for MOE (minute of elk) but the different in hitting a prairie dog or not at 600 is alot. Target model scopes almost always have some form of parallax adjustment (leupolds have it on some models on the end of the bell).
> 
> -DallanC


I learn something new all the time on this site. Dallan C, what would you think would be some of the best "mid-priced" scopes on the market?


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## DallanC (Jan 13, 2009)

colorcountrygunner said:


> I learn something new all the time on this site. Dallan C, what would you think would be some of the best "mid-priced" scopes on the market?


Gotta give me a $ range... "mid-range" is subjective. Also would you consider used scopes with lifetime warrenties?

I have a few favorites, but we probably should get Loke to chime in as he's up todate on the latest offerings.

-DallanC


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## stillhunterman (Feb 15, 2009)

Thanks Dallan, interesting. I shot a peep sight for several years, then when my eyes started to change went to a fixed (4 power) for several more years. Then, just because, I went to variables. Funny, I always sighted in at 4 power on the variables and rarely used higher magnification in the field or at the range, except when still hunting in the trees I would drop down to 2.5 or 3.

Trying to find a new cartridge to shoot I've been using my scope out to 12 at the range and down to 4, thus I found the difference in point of impact I referred to. I have a Nikon Monarch 3 and it doesn't have a parallax adj on it, which is no issue for the hunting I do, so MOE should be good to go :mrgreen:

It's been a great scope over the years, couldn't ask much more of it. Anyway, thanks for the info!


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## DallanC (Jan 13, 2009)

My boy bought his first rifle last year, a 7mm08 and after a bit of research I decided to try a Nikon Buckmaster 3x9 scope. We picked a used one up off Ebay for just over $100. Its been a really impressive scope, doubly so considering the price. Buckmaster is right between the Prostaff and the Monarch scope lines in terms of quality. People rated it better than the Leupold Rifleman.

Almost all my other rifles wear Leupolds, in many different powers. 3x9's, 4x12's and my 7STW wears a 6.5x20. Bought a 4x12 Nikon P223 scope for an AR, it has the BDC drop reticle on it and its been spot on and very fun to use.

So as is, Leupold's are my first choice followed by Nikon's... 3rd place would probably be a Vortex scope of some flavor (got a vortex spotter, been very impressed with it).


-DallanC


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## stillhunterman (Feb 15, 2009)

DallanC said:


> My boy bought his first rifle last year, a 7mm08 and after a bit of research I decided to try a Nikon Buckmaster 3x9 scope. We picked a used one up off Ebay for just over $100. Its been a really impressive scope, doubly so considering the price. Buckmaster is right between the Prostaff and the Monarch scope lines in terms of quality. People rated it better than the Leupold Rifleman.
> 
> Almost all my other rifles wear Leupolds, in many different powers. 3x9's, 4x12's and my 7STW wears a 6.5x20. Bought a 4x12 Nikon P223 scope for an AR, it has the BDC drop reticle on it and its been spot on and very fun to use.
> 
> ...


Yep, I used the Leupolds for a long while and they are still my fav. Went to a Nikon for a 'change of flavor' and it tastes sweet  Leupold is still my #1 but not by much, with Nikon a really close second.


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## Elkoholic8 (Jan 15, 2008)

My favorite for "affordable" scopes, is Leupold also. I purchased a Nikon Monarch a couple years back and I loved looking through the glass. I am a little mixed over the BDC reticle (not sure I like all the circles being the same size), But last year I found a major problem with the Nikon scope. With the rifle hanging on my shoulder, and the gun moving lightly as I walked, the eye piece on the scope would come out of focus. I pulled up on an elk and could not see anything beyond 10 feet. It was like someone breathed on the lens. The eyepiece had unscrewed almost all the way out. I sent it back to Nikon after the season, and they replaced the scope, but I think the new one is just as easy to turn. Their suggestion was to leave the flip up eye cap on the eye piece (it's a smooth finish therefore shouldn't turn my rubbing on your jacket). 
With that said, I wish Nikon and the other brands would have a lock ring on their eyepiece like Leupold. I have also checked out some Vortex, and been very impressed!


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## Bax* (Dec 14, 2008)

Where you will notice POI shift is if you have some sort of BDC reticle or multiple crosshairs below the main crosshair. These will shift POI when changing magnifications so you need to learn how they behave at different magnifications. But the center crosshair should remain constant.


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## RandomElk16 (Sep 17, 2013)

Bax* said:


> Where you will notice POI shift is if you have some sort of BDC reticle or multiple crosshairs below the main crosshair. These will shift POI when changing magnifications so you need to learn how they behave at different magnifications. But the center crosshair should remain constant.


This^^

The center of the reticle is always going to be the center of the reticle. As the field of view expands when lowering the power, your BDC changes.

As best practice I sight in at highest power.


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## Cooky (Apr 25, 2011)

Bax* said:


> Where you will notice POI shift is if you have some sort of BDC reticle or multiple crosshairs below the main crosshair. These will shift POI when changing magnifications so you need to learn how they behave at different magnifications. But the center crosshair should remain constant.


Only with a second focal plane scope. 
With first focal plane scopes the values remain constant as magnification changes. The values remaining constant in a FFP scope is a big help when using holdover rather than dialing for elevation, you don't have to return to the magnification the values are set at or do mental math when you don't.


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## Longgun (Sep 7, 2007)

It's easy enough to check. Just adjust your scope for the appropriate range and center it on a target at that distance with the rifle sitting on a solid rest. Adjust out the parallax with the objective focus. Then carefully zoom the scope and look for any shift between the target and the reticle. Repeat to be sure any movement is caused by the zoom and not by rifle movement. If zooming does not cause relative movement of the image relative to the reticle then it's not affecting POI. If there is relative motion between the reticle and the target image then it must affect POI. If the reticle is located AFTER the zoom mechanism then there is potential for the POI to be affected. How well the scope is designed and constructed will determine if it actually takes place. 

Obviously if you're using a second focal plane reticle for hold offs using reticle markings as the reference you will get large POI errors as you change the magnification. That will also happen if a second focal plane reticle isn't properly centered on the optical axis and you use only the crosshair center. That is not normally an external adjustment. 

Parallax error can change with a poorly designed second focal plane reticle following a zoom. Even if the scope is perfectly designed high magnifaction will make the parallax error appear larger. The converse of that is that low magnification may cause you to ignore parallax error which is significant. 

I general I prefer fixed magnification scopes, or at least scopes with first focal plane reticles. Variable scopes with second focal plane stadia reticles are just an invitation for errors. Some "ballistic drop compensated" scopes actually rely on the offsets generated by the zoom optics. They work fairly well when matched to the ballistics of specific cartridges but only if they're used as intended. (Leatherwood ART scopes for example).

The bottom like is to know your equipment thoroughly and use it in the way it's designed to be used. Don't assume you're doing it right without target shooting at the ranges you expect to hunt. If you can't hit fixed targets accurately you certainly can't make clean kills on game in the field.


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## Frisco Pete (Sep 22, 2007)

Maybe some further explanation can help:

The reticle can be placed in two different positions in the scope:
_*First*_ or _*front focal plane*_ reticle placement is common on European scopes. These scopes have the reticle placed in the objective end, or forward of the erector system. This causes the reticle to be magnified at the same rate as the target. When you increase the magnification the reticle will continue to cover the same amount of the target as it did at low magnification.
One advantage of having the reticle in the first focal plane is with a multi-point mil-type reticle because it stays the same size relative to the target. 
Most American made scopes (_including those made for U.S. companies in the Far East_), have the reticle placed in the _*second*_, or _*rear focal plane*_. In this position, the reticle will not be magnified at the same rate as the target. In other words, when you increase the magnification on a rear focal plane scope, the reticle will subtend less of the target than it does at low magnification. For the majority of hunting applications in the US, positioning the reticle in the 2nd focal plane is desirable. The biggest drawback to our common second focal plane scopes is that on variables, they are susceptible to POI shift as the power is zoomed. Careful construction helps eliminate this, but it is not an issue with first focal plane scopes as that part doesn't move when zooming. 
Most European scopes have the reticle in the first focal plane and the reticle will remain constant, however quite large on high magnification. For most American hunting applications it is too large. Most European hunting is not done at such long distances. 
Many tactical groups prefer front focal plane designs because common tactical reticles serve a dual purpose: a point of aim and a means of measurement. Reticles such as a mil dot are based on a specific subtension and require exact feature spacing to be accurate; if this type of reticle is used in a rear focal plane design, the scope must be used on a single, specific magnification (_typically high power_). Placing this type of reticle in a front focal plane design allows the operator to use the scope on any magnification while retaining the exact spacing of the reticle features.

If the reticle cell has shifted, due to time and recoil, it will create excessive parallax, meaning the reticle apparently wanders around the aiming point when you shift your head behind the scope. Groups tend to string up and down when this happens. The reticle cell can also come loose. I have had this happen to the reticle on a cheap Chinese SKS scope which turned the reticle into an "X" after a minor amount of use. You can't hit anything when this happens either!

*PARALLAX*
A condition that occurs when the image of the target is not focused precisely on the reticle plane. Parallax is visible as an apparent movement between the reticle and the target when the shooter moves his eye anyplace but dead-center behind the scope's field-of-view - or, in extreme cases, as an out-of-focus image.
Most center-fire riflescopes under 11x are factory-set parallax-free at 100 yards; rim-fire and shotgun scopes at 50 yards. Any scopes over 10x requires some sort of method to eliminate parallax. These scopes usually have a special range focus (adjustable objective or AO) to adjust for parallax. Newer and tactical versions often feature a side-adjustment, normally placed on the left side of the scope opposite the horizontal turret adjustment. Parallax is really apparent when you try to focus on a target with a standard rifle scope at 25 yards. The crosshairs seem to "float" around as you slightly move your head/eye behind the scope.
As mentioned in the section above - if the reticle cell has shifted, due to time and recoil, it will create excessive parallax, meaning the reticle apparently wanders around the aiming point when you shift your head behind the scope. Groups tend to string up and down when this happens.


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