Rifle Scopes FFP vs. SFP in terms of Actual POI

[topslop1]

I have heard a lot of talk about FFP vs. SFP scopes and I'm really curious to see if anyone has done a point of impact test showing how a SFP scope changes over magnification differences and distances. Since there are a lot of lower powered scopes, including Night force etc that are SFP, how much of an impact difference are we really going to see in real world application?

 

[Quickdraw40]

Ummm... If I understand your question, the reticle covers 2x at 11 instead if 22. No need to do a real world test to verify this.

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[Lowlight]

I think he is talking about the Bench Rest talking point that certain scopes move their impact with power adjustments.

It's hard to say he is not very clear in his question.

 

[topslop1]

I think he is talking about the Bench Rest talking point that certain scopes move their impact with power adjustments.

It's hard to say he is not very clear in his question.

Sorry, yes I am asking about this.

 

[Rob01]

Any quality variable, whether SFP or FFP, should not have any discernible POI shift when dialing the power range. Years ago this was a problem but with the way scopes are made it's not anymore. If you find a scope that does it it should be sent in for service.

That said some people try and shoot at the same 1" dot they shoot at on 22x with their scope on 5x might have a problem. Adjust the target size to the power setting and there should be no difference. I use an 8" shoot n c when i shoot my 1-6x at 100 yards to check it. It's large enough to quarter on 6x. Using a 1" dot would be very hard to get a good aiming point.

 

[Deleted member 10043]

Quickdraw, what did you like about Lowlights post. He said he "thinks" and it is "hard to say". He was trying to get the OP to clarify his question.

It implies right on the instruction for Leupold scope reticles that the POI will change. Example, variable power scopes with hunting reticles. Magnification is adjusted to match bullet drop. The Leopold LR Duplex and the Rifleman Ballistics reticles are the same reticle. Look up the pdf instructions. It's right there. You get your scope set at 6.5x to match the elevation marks on the scope and find it is accurate. You then change the magnification and now your POI has changed significantly. So yes, it is true but depending on your reticle it can be used to your advantage. It doesn't mean there is something wrong with the design of the scope. Also, if you have Strelok+ you can simulate this with that reticle tool Igor programmed into the app. The attachment with holdovers set at 200, 300, 400, 500 is set at 6.5x. The other one is set at 9x. These are for the same ammo. Notice the change in POI?

 

[Quickdraw40]

Quickdraw, what did you like about Lowlights post. He said he "thinks" and it is "hard to say". He was trying to get the OP to clarify his question.

I don't have to answer to you what I like about anyone's post.

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[SNAFU308]

Quickdraw, what did you like about Lowlights post. He said he "thinks" and it is "hard to say". He was trying to get the OP to clarify his question.

It implies right on the instruction for Leupold scope reticles that the POI will change. Example, variable power scopes with hunting reticles. Magnification is adjusted to match bullet drop. The Leopold LR Duplex and the Rifleman Ballistics reticles are the same reticle. Look up the pdf instructions. It's right there. You get your scope set at 6.5x to match the elevation marks on the scope and find it is accurate. You then change the magnification and now your POI has changed significantly. So yes, it is true but depending on your reticle it can be used to your advantage. It doesn't mean there is something wrong with the design of the scope. Also, if you have Strelok+ you can simulate this with that reticle tool Igor programmed into the app. The attachment with holdovers set at 200, 300, 400, 500 is set at 6.5x. The other one is set at 9x. These are for the same ammo. Notice the change in POI?

Your POI doesn't change the hold off marks changes as the magnification changes as it's not FFP but the POI at the centre duplex should remain the same at all magnifications

 

[Deleted member 10043]

The OP was also asking about distances. But I agree and I cannot explain why the 200 yard zero would stay the same and the others change. There has to be some degree of shift to the contrary. Sounds like physics to me. For every action there is a....

 

[SNAFU308]

The OP was also asking about distances. But I agree and I cannot explain why the 200 yard zero would stay the same and the others change. There has to be some degree of shift to the contrary. Sounds like physics to me. For every action there is a....

It's very easy to explain it's because the reticle images you posted for SFP scope at different magnification ranges. Without getting into depth about the difference between FFP and SFP (it's been done enough) with SFP the reticle does not stay constant in relation to the target like with FFP. If it was a FFP scope those sub-tensions would be correct at all magnifications but with a SFP the reticle does not change so the hold offs change as you change the magnification. He was asking if there was a point of impact shift with SFP scopes and if so was it more prevalent at longer ranges, at least that's how I understood it. Not how do SFP reticle sub-tensions change through the magnification range.

To the OP I have not noticed any POI shift when changing the magnification on my SFP scopes even at longer ranges. With my old Nightforce NXS I would often change the magnification particularly at longer ranges when mirage was a issue and didn't notice any POI shift.

 

[Deleted member 10043]

there has to be shift. It does not make sense that a 200 zero remains constant at all magnications but changes over distance. The only thing for certain is it is harder to observe and immaterial. I find it hard to believe that 1 yard past 200 is where physics takes over.

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[Lowlight]

The Bench Rest guys are talking about movement with the POI at their zero range with a change of magnification.

Their reticles are not used for holds so that is a non-issue, we all know SFP reticles only work on one power to be true, however the question is about a moving point of impact based on the center crosshair.

They are shooting for tiny groups and in the past some have observed movement in the zero. That is what he is talking about

 

[Deleted member 10043]

The hold overs are illustrated to work back to the crosshairs. Why would it be exactly 200 yards at any magnication? I would lean towards the anal benchrest shooter theory.

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[SNAFU308]

The hold overs are illustrated to work back to the crosshairs. Why would it be exactly 200 yards at any magnication? I would lean towards the anal benchrest shooter theory.

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Not trying to be rude but I think you need to look into the difference between FFP and SFP a little more as you seem to be misunderstanding why the hold overs change and it isn't related to what the OP is asking. the centre crosshair is exactly 200 yards at any magnification because that's where they're saying it's been zeroed. The scope has a 200 yard zero and as lowlight has indicated the hold overs on a SFP scope are only true at one magnification after you change that magnification level the hold overs have changed in relation to the target and is why you see two different distances listed in the pics you attached.

As has been stated earlier with todays high end scopes there really shouldn't be any POI change through the magnification range and I haven't noticed any even at 1000 yards

 

[CMH]

The Bench Rest guys are talking about movement with the POI at their zero range with a change of magnification.

That explains why Nightforce was hitting no change in POI across the magnification range in the Competition line. It seemed like a weird thing to be focusing on when I first saw it.

 

[Lowlight]

Exactly, the contention has nothing to do with range, or holdovers, it's the center of the crosshair.

The test can be done at 100 yards but you'd need a very accurate rifle, one capable of at least .25MOA on a consistent basis. Anything more you won't see it. It's small.

Confirm zero, the shoot it at multiple power settings to check for any deviations. It was more a problem 20 years ago, as methods have improved since that time. I believe the claim was against FFP scopes as opposed to Second. Which is why you see more SFP used in F Class and Bench Rest.

 

[BERTMAN77MK2]

Thanks Lowlight, I always wondered why the benchrest competititors used SFP scopes.

 

[Lowlight]

The reticles on a SFP are more in tuned to their type of shooting, there is very little reason to have a target dot in a FFP scope.

In terms of overall thickness, you tend to have thicker reticles with a FFP scope because they have to adjust, so in order to be useful at lower magnifications the companies make them thicker. In a SFP it does not matter when you are just using the center, so they can be made sub-MOA (very thin) without the issue of having to shoot it on 6x or lower. Very rarely do you have of SFP shooters off max power except for things like mirage mitigation.

The Dual Use / Tactical Use is a fairly new concept in terms of sport shooting. Even hunting wise, LR Hunting is a fairly new concept, most of it was done 300 yards and in, so there was no reason to worry about holds or adjustments in the reticle itself.

 

[Deleted member 10043]

WTF, so, yes, there is difference.

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[delixe]

WTF, so, yes, there is difference.

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In the past, SFP scopes exhibited some shift in POA (point of aim) at the center of the reticle when the magnification was changed, while FFP scopes did not exhibit any such shift.
The result of this shift would be that if you zeroed your scope then changed the magnification and fired again, there would be a slight change in POI. It is a by product of the difference in the way an SFP scope is built vs. an FFP scope. It is not related to the fact that an SFP reticle only subtends properly at one magnification. That is a "feature" of its design and is predictable, i.e. if an SFP reticle subtends correctly at 22x, then the angular values (reticle hash marks denote angular values, not linear) double at 11x, so the 1MOA (minute of ANGLE) hash mark becomes 2MOA

For that reason, SFP BDC reticles only work at their stated differences at the magnification they were designed at. Let's say a 300 yard BDC hash mark equates to 6.5 MOA at the scope's reference magnification. At half that magnification, the same hash mark will equate to 13 MOA. If you have a load that requires 13 MOA of hold at some given distance, that could be useful, but if you shoot the ammo the BDC was designed for at half magnification using a BDC hash, it's gonna be quite a bit high at that distance.