Impact Shift on NF NXS 2.5-10

[Alex Genereux]

On a second focal plane scope if you dial to half total magnification (5) all the hash marks are just halved pretty easy to remember.

 

[Macintosh]

So, I ran across this:

"Another unique feature: the Schmidt & Bender patented “Minimum Deviation Technology” allows only a negligible deviation of less than 1 cm at 100 m (0.39” at 109 yd). This is essential for achieving the highest precision since every Second Focal Plane riflescope suffers deviation when rotating the magnification from maximum to minimum."
from: https://www.schmidtundbender.de/phocadownload/flyer/Flyer_Polar-T96-Series_EN.pdf

This is on a scope with no hashmarks on any of the reticles offered, so I don't think it's a translation issue of the hashmarks, or anything like that. I had never heard of this before, but it sure sounds like they are talking about the zero at the crosshair shifting during a magnification change on a 2fp scope, and they are claiming it is universal across all 2fp scopes. Anyone?

 

[nobody]

yup, thank you, that's exactly what I'm asking

As long as the scope isn't made of plastic and tissue paper, the central point in space won't have any change. A center point in space is the center point in space, independent of the level of magnification.

What WILL change, however, are your "BDC" points, and their values at different distances. That's because the image will grow and shrink as you zoom, but the reticle doesn't and so at a low magnification, the first hashmark is further away from the centerpoint on your crosshair relative to the animal, and at higher magnification it's closer. It makes judging drop at distance a b***** under pressure (speaking from experience).

Here's an example with a 3-9 Variable optic:
You're zeroed at 100 yards, and let's say on max power your first hashmark is the right distance for a 200 yard drop (Second Focal Plane). But who is going to shoot an animal at 200 yards on 9x mag? So you dial down your magnification to, let's say, 5x. If you still use that first hashmark to try to kill that deer, you will probably shoot over it.

Do the same thing with a First Focal Plane optic, and your second hashmark equals your drop to 200 yards whether it's on 3 or 9 power or anything in between.

FFP takes the mental gymnastics out of holding with a reticle if you have to. That said, your best solution is to purchase an FFP optic, learn ballistics, dial elevation, and hold your wind.

 

[Macintosh]

I would have answered exactly the same yesterday—thats exactly what Ive always been told, and I never noticed otherwise. BUT, take a look at that S&B link I just put above^^, it says otherwise. I am curious if someone can address that squarely?

 

[ID_Matt]

On a second focal plane scope if you dial to half total magnification (5) all the hash marks are just halved pretty easy to remember.

Aren't they doubled, not halved?

 

[ResearchinStuff]

circa 2009 nightforce marketing for the NXS line mentioned that there was no POI shift when magnification changed. My dad was pretty impressed by that claim, but in my infinite wisdom I bought a Leupold MK4 instead of the NXS 5.5-22.

 

[nobody]

I would have answered exactly the same yesterday—thats exactly what Ive always been told, and I never noticed otherwise. BUT, take a look at that S&B link I just put above^^, it says otherwise. I am curious if someone can address that squarely?

I'll put it this way, there might be some shift. But the shift will be so minimal (IE less than the accuracy level that anybody can shoot with a hunting weight rifle) that if you're losing zero or missing, it's not because you're on the "wrong magnification." If you're worried about the shift, pick up a fixed power optic like an SWFA, then you don't have any magnification change to worry about.

I also bet that a lot of the shift with a magnification change is due more to parallax error than anything. Magnifying an image also magnifies imperfections and makes them easier to pickup, including errors in parallax. Parallax error at 600 yards won't necessarily be the reason you miss, but it could explain a few inch shift in POI vs. POA, all other variables held steady.

If anybody out there can consistently put EVERY single shot inside 1CM (not a 3 round group, not a 10 round group, EVERY SINGLE shot) with their hunting rifle, I'll eat my Tikka. Not with "excluding that one flier," not with warm up shots, not with a fouler, I'm talking every last round through a rifle, from shot 1 to shot 10,000. That S&B post sounds like a bunch of marketing "geniuses" decided to make a mountain out of a molehill and hang their hat on it. Reminds me of Leupold's "50,000 G's of force" or whatever the heck it was.

My answer stands, a center point in space is a center point in space. Center of crosshair is center of crosshair, independent of magnification. What changes are all other visible points in the view relative to the center point (in modern optics properly constructed, of course). If we are talking about older or sub-par optics, then my post is null and void. But if a scope is failing that poorly, it's probably failing in other ways and you're probably already noticing other issues, so the shift with magnification just becomes a tally mark against the optic.

 

[Formidilosus]

I think some clarification is needed.

Yes- SFP scopes will show some point of impact variation of the center aim point as the magnification is changed. It’s pretty minimal on modern “good” scopes, but even still most do feature enough that it could be measured.
Now, is it enough to make a difference on animals with quality scopes? Probably not. But it is real. I don’t shoot nearly as much with SFP as I used to, but a decade or so ago .5 to even 1 MOA poi shift wasn’t uncommon from lower to high powers in SFP scopes.

If I were using a SFP seriously, I would zero it on the power that I actually would be doing most of the important shooting at; or at least do a thorough check throughout the mag range.

 

[Macintosh]

Edit: thanks Form, that makes sense.