First experiences (oddities) with FFP

[rbernie]

I recently decided that I wanted an inexpensive FFP optic with MOA adjustments / reticle (since I'm used to working with imperial units of measure), positive zero stops, and a reticle with enough contrast in the subtensions for my bad / aging eyes to use at intermediate zoom settings. I really don't know much about what I'm doing in this particular area, and buying-and-trying seemed like a good way to start learning. I went through a bunch of side-by-side comparisons at my FLGS, and eventually settled on a Sig Tango4 (FFP) 6-24x as a low-cost entry into the genre. In particular, the glass quality (relative to cost) and the reticle crispness sold me on the Tango4.

In sighting it in, it quickly became evident that the reticle was visually moving from center as I zero'ed the rifle. In other words, the reticle would not remain centered in my field of view as I moved the turrets through their adjustment range. I had never encountered anything like this, and I found it very visually distracting to NOT have the reticle centered in my field of view. I went back to the store to see if this was common to FFP optics in general or if my specific scope was defective in some way. Frankly - I assumed my scope was broken.

We first called Sig to get their opinion, and they said that this behavior was normal. I really didn't trust that feedback, and so we then compared my Tango4 to other Tango4's and various Vortex and S&B offerings in inventory, to see how common this behavior really was. All told, I probably spent two hours twiddling knobs and looking at reticles.

What I came to learn is that the observed behavior is normal across the Tango4 line; we could duplicate it in other Tango4's with absolute repeatability. I also found that I could duplicate this behavior to some degree in the Vortex Diamondback Tacticals and the FFP Vipers. Interestingly, I could -not- duplicate this behavior in any of the Tango6 or Razor or S&B optics in stock; there was clearly a behavioral discrimination between the lower cost (sub-$1200) offerings and the more upscale optics.

So here I am, with virtually zero stick time yet in the field, and I've learned an important lesson in FFP optics - if you want the mechanical elegance of a reticle that remains centered as you adjust the turrets, you gotta pay to play.

<sigh>

 

[Walkalong]

Tough way to find out.

 

[rbernie]

Why does nobody ever mention that in the product reviews?

 

[Skylerbone]

Would your LGS be inclined to add to his inventory of demo units? That’s disappointing to be sure and something I’ve yet to see mentioned in any review. My only FFP is a Pride Fowler RR-800 and I’ve never experienced that phenomenon despite the rather modest price tag at the time, around $700 I believe.

 

[Odd Job]

It seems bizarre to me that this would be a natural "feature" of a cheaper scope. Doesn't it then make the scope not fit for purpose?
Who would buy a scope that has to be windage adjusted every time you zoom it?

 

[rbernie]

Who would buy a scope that has to be windage adjusted every time you zoom it?

The reticle movement isn't related to zoom - it's related to turret position, at any zoom. As you zero the rifle (adjust POA to POI), the reticle moves within the circular field of view. Ultimately, in my case, it wound up off-centered towards the upper left by a noticeable amount.

 

[Odd Job]

Ah, I completely misunderstood the issue you were having.

 

[Legionnaire]

... As you zero the rifle (adjust POA to POI), the reticle moves within the circular field of view. Ultimately, in my case, it wound up off-centered towards the upper left by a noticeable amount.

That's just weird. I don't recall looking through any scope in which the reticle was not centered. The exception would be the ranging reticle eye-pieces that were once available for Vortex Razor spotting scopes, which were designed with the reticle off center so as not to block central field of view (that was a cool feature).

 

[Varminterror]

None of my Tango4’s shift with zoom or “turret twisting.” But I only have 3 of them.

 

[<*(((><]

So let me make sure I’m understanding correctly.

When the turrets (both windage and elevation) are at the exact halfway point between their adjustment (I.E. if they have 100 clicks of adjustment each they are both sitting at 50 clicks from one side or the other). If this is the case the reticles crosshair intersection is centered in the objective when looking through the scope. Correct?

Now when you are adjusting for POA to match POI and adjust both the windage and elevation the reticle crosshair intersection will be out of center in the objective when looking through the scope. Am I understanding what you are saying?

So if you turned the turrets to the extreme the problem is exacerbated to where it is really noticeable.

I’ve never owned a FFP but my next scope has the potential to be one and just want to understand this correctly so I know what to look for. If this is the case that’s a definite downside as if one is adjusting the elevation for a long shot and utilizing the scopes max elevation adjustment there will be less useable field of view on the one side of the target down range.

 

[wally]

That's just weird. I don't recall looking through any scope in which the reticle was not centered.

The Russian PSOP style scopes are made this way. If you are doing long range and using reticle hold over it lets you have more "ticks" below the zero whereas all the ticks above the zero are generally "wasted" -- you'll only need a couple of hold under ticks for closer range if zeroed for 300.

If the windage is significantly off center when zeroed, I'd suspect the mounts aren't quite right. They do make "windage adjustable mounts if needed, but adds one more thing to mess up, so IMHO best avoided if possible.

I don't know the Tango 4 design, but what the OP describes is not a totally irrational way to build a scope -- clearly not popular in the USA.

 

[Skylerbone]

The Russian PSOP style scopes are made this way. If you are doing long range and using reticle hold over it lets you have more "ticks" below the zero whereas all the ticks above the zero are generally "wasted"

I don’t think that’s what’s at issue here, unless I’m mistaken. My Rapid Reticle is the same, with 400 yards being level with the center hash. Those with Zeiss’s “Rapid Z” reticle will recognize this one as Pride Fowler licensed it for use to Zeiss. Same idea as building cant into the scope and this is what it looks like when fully zoomed (9X).

 

[Legionnaire]

Yes. I should have been clearer. The "off center" reticle Skylerbone shows above makes total sense. What I read from the OP is that when making adjustments, the vertical is moving east and west. That is what I was reacting to.

 

[wally]

Yes. I should have been clearer. The "off center" reticle Skylerbone shows above makes total sense. What I read from the OP is that when making adjustments, the vertical is moving east and west. That is what I was reacting to.

That is what the PSOP scopes do, for both windage and elevation if there is "cross-talk" in the adjustments something is wrong with the scope.

 

[rbernie]

When the turrets (both windage and elevation) are at the exact halfway point between their adjustment (I.E. if they have 100 clicks of adjustment each they are both sitting at 50 clicks from one side or the other). If this is the case the reticles crosshair intersection is centered in the objective when looking through the scope. Correct?

Now when you are adjusting for POA to match POI and adjust both the windage and elevation the reticle crosshair intersection will be out of center in the objective when looking through the scope. Am I understanding what you are saying?

This is correct. It was repeatable across a number of examples, and a call to Sig indicated that this was considered normal for their design.

It may have been that my zero was sufficiently offset as to render this behavior more observable than it might be on other rifles, but turning the turrets well off center and closer to their limits clearly exposes the behavior.

 

[<*(((><]

This is correct. It was repeatable across a number of examples, and a call to Sig indicated that this was considered normal for their design.

It may have been that my zero was sufficiently offset as to render this behavior more observable than it might be on other rifles, but turning the turrets well off center and closer to their limits clearly exposes the behavior.

Glad I know that this is normal for Sig scopes as I won’t be buying one of them. I can see how it may be beneficial on elevation if it gives one more holdover at distances like the others have posted with specialized reticles. But that is absurd for the windage adjustment to offset the reticle if there is another way of doing so, so that it doesn’t.

I guess maybe I’m making it out to be more than it is, it just seems hokey to give up field of view on one side of the reticle.

I wonder if the Vortex FFP vortex is the same way?

 

[rbernie]

I wonder if the Vortex FFP vortex is the same way?

The Viper and Diamondback FFP showed this behavior to a small extent (we really had to look critically to see it) but the Razor’s did not, nor did the Tango6 or the S&B (I forget which one) that they had in stock.

Glad I know that this is normal for Sig scopes as I won’t be buying one of them.

It would not be fair to say that all Sig optics do this; that would be fair to say that the current production Tango4 does this, with Sig’s knowledge and blessing.

it just seems hokey to give up field of view on one side of the reticle.

My principal quarrel with the behavior was that it meant that centering up on the optic in a repeatable position with a repeatable field of view was not possible; either I was centered on the rifle with an offsite reticle in my field of view or I attempted to center on the reticle which then pulled me off the rifle (and didn’t really work anyway because no matter what, the reticle was always offset in the ocular).