What kind of point of impact shifts will I see when using my Nightforce 2.5-10 which is a second focal plane scope? If I'm shooting at 100m and say I'm shooting .223 out of an 18'' barrel what kind of impact am I likely to see between 2.5x and 10x magnification? How much would I see between 2.5x and 10x at 300m or 600m? This is a question that I've not been able to test yet and have had great curiosity about.
Rifle Scopes SFP POI shift?
- Thread starter topslop1
- Start date
Re: SFP POI shift?
there shouldn't be any change of POI from changing magnification
there shouldn't be any change of POI from changing magnification
Re: SFP POI shift?
The difference comes in if you have a reticle like say an npr1 or mildot. With a SFP the center of your reticle will stay zeroed at any power but lets say you have a mildot. The mildots will only be equal to one mil at a certain power setting. Lets say 10x which is prob the case with your scope. If your set at 10x those dots are worth exactly 1 mil, if you are set at any other power they are not because as you increase or decrease the size of the image the reticle stays the same size. With a FFP the reticle increases and decreases with the image so your subtensions on your reticle stay true at any power setting
The difference comes in if you have a reticle like say an npr1 or mildot. With a SFP the center of your reticle will stay zeroed at any power but lets say you have a mildot. The mildots will only be equal to one mil at a certain power setting. Lets say 10x which is prob the case with your scope. If your set at 10x those dots are worth exactly 1 mil, if you are set at any other power they are not because as you increase or decrease the size of the image the reticle stays the same size. With a FFP the reticle increases and decreases with the image so your subtensions on your reticle stay true at any power setting
Re: SFP POI shift?
A high quality SFP scope shouldn't see any between power deviation as it is usually tested for and built in a manner that ensures there is no shift. I know that Nightforce does check for this during their inspections of each scope.
Lesser quality scopes can and sometimes do have some between power deviation as it takes time and money to ensure it doesn't take place. The deviation comes from the erector assembly where the glass is moving back and forth to create the variable magnification. If the erector assembly isn't perfectly manufactured and the lenses indexed you'll get the deviation at different magnification. This is only an issue in SFP scopes because the reticle is behind the erector assembly which allows for the misalignment. FFP optics have the reticle in front of the erector assembly so it is independent of the erector assembly positioning in regards to any potential deviation between magnification.
In short, there is a reason you spend more on good optics.. it prevents little issues like between power deviation.
-Sean
A high quality SFP scope shouldn't see any between power deviation as it is usually tested for and built in a manner that ensures there is no shift. I know that Nightforce does check for this during their inspections of each scope.
Lesser quality scopes can and sometimes do have some between power deviation as it takes time and money to ensure it doesn't take place. The deviation comes from the erector assembly where the glass is moving back and forth to create the variable magnification. If the erector assembly isn't perfectly manufactured and the lenses indexed you'll get the deviation at different magnification. This is only an issue in SFP scopes because the reticle is behind the erector assembly which allows for the misalignment. FFP optics have the reticle in front of the erector assembly so it is independent of the erector assembly positioning in regards to any potential deviation between magnification.
In short, there is a reason you spend more on good optics.. it prevents little issues like between power deviation.
-Sean
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