Rifle Scopes Scope validation vortex/nightforce atacr/uso.

[Uspsa2011]

After missing engagements I couldn't explain I began to believe that my scope may not be tracking properly. Borrowing advice from previous threads, I started toying with the idea of building a scope tracking fixture. With the fabrication skills of a close friend we (he) had a fixture built to test a scopes ability to track. A "humbler" if you will, for those who recall an old scope tracking thread. There was a thread on the old site that seemed to have magically disappeared where "kse" tested the mechanical tracking ability of various scopes. Many of these ideas were borrowed from "kse", and his "humbler" rig.
The scope I had in question was a vortex razor gen 1 with 10 mil/rev turrets. It didnt take long to figure out that there was .2 mil extra indicated on the reticle with 10mil dialed. In other words if I dialed 10 mil the reticle moved 10.2 mil.

With that confirmed we moved on to other scopes we had. One of those scopes was a nightforce 5-25 atacr 2nd focal. The image posted is of the nightforce. Notice the center crosshairs and the 4th mil on the reticle. The etching in the reticle seems off by between .1 and. 2 mil. Best I can see, it's off by right around .15 to .16 mil. How likely is it that the reticle etching is not totally accurate?

 

[Dthomas3523]

If your measurements are correct for the give distance......looks like it.

 

[Dthomas3523]

Also, being 2nd focal, is it possible the magnification is slightly off where the subtensions reflect the proper measurements?

Have you messed with the zoom ring to see if it correctly subtends with a little more or less zoom?

 

[Uspsa2011]

To try and answer some questions before they are asked, many variables in this test were vetted. The target was measured, and multiple scopes were tested. Distance of 100 yards was confirmed with a 300' tape along with a laser rangefinder. The other scope tested was a uso 3-17. The etching on the uso lined up perfectly with the marks on the target. The etching on the gen 1 razor was close to perfect. The etching on the nightforce atacr was between 1 and 2 clicks out at the 4 mil line.

 

[Uspsa2011]

Magnification on the nf was set at max. 25x.

 

[Precision Underground]

Strange thing is if you put calipers on the picture the mil from 3-4 is smaller than the 0-1 mil. Could possibly be an illusion created by the camera angle but if you were seeing that with your eye it prob is not. It almost looks like each mil gets progressively smaller from 1-4.

 

[Dthomas3523]

Magnification on the nf was set at max. 25x.

Have you backed the power down ever so slightly to see if the problem is the magnifier is not working as close as the numbers suggest?

 

[Precision Underground]

Measuring on a larger screen the 3rd mil seems to be the smallest compared to the first mil. And each one is compounding the next.

 

[Uspsa2011]

@ dthomas. Didn't try backing down the magnification due to the fact that other scopes at the same distance reflected truer subtensions.

@ jpgolffl. Pretty much the same response. Other scopes, though first focal plane, showed the subtensions more accurately. Not sure how you were able to measure the distance between subtensions from the pic. As far as optical discrepancies, parallax was dialed out as best as it could be. Also worth noting is 3 different person's were able to observe matching observations through the different optics. Camera angle could certainly play a role but I would imagine that 3 person's verifying through multiple optics would help negate that possibility.

 

[ShtrRdy]

It looks to me that the magnafication ring is slightly off to calibrate the SFP reticle.

 

[Precision Underground]

@ dthomas. Didn't try backing down the magnification due to the fact that other scopes at the same distance reflected truer subtensions.

@ jpgolffl. Pretty much the same response. Other scopes, though first focal plane, showed the subtensions more accurately. Not sure how you were able to measure the distance between subtensions from the pic. As far as optical discrepancies, parallax was dialed out as best as it could be. Also worth noting is 3 different person's were able to observe matching observations through the different optics. Camera angle could certainly play a role but I would imagine that 3 person's verifying through multiple optics would help negate that possibility.

Just put a caliper on the pic and measure it. Like I said it’s possible that the angle of the camera makes the measurement off but considering you were seeing the same thing with your eye my verdict would be that the reticle is off a little bit. If the measurement is correct it would mean it’s a reticle issue not a magnification issue. If it’s a magnification issue you should see the same deviation horizontally on the reticle as well.

 

[Dthomas3523]

@ dthomas. Didn't try backing down the magnification due to the fact that other scopes at the same distance reflected truer subtensions.

@ jpgolffl. Pretty much the same response. Other scopes, though first focal plane, showed the subtensions more accurately. Not sure how you were able to measure the distance between subtensions from the pic. As far as optical discrepancies, parallax was dialed out as best as it could be. Also worth noting is 3 different person's were able to observe matching observations through the different optics. Camera angle could certainly play a role but I would imagine that 3 person's verifying through multiple optics would help negate that possibility.

Weren’t the other scopes FFP though?

 

[Uspsa2011]

Good call. I didn't think to look horizontally. I'll take a look at that next time I get a chance.

 

[Uspsa2011]

Weren’t the other scopes FFP though?

The other scopes were ffp. The atacr reticle should line up the same as the ffp scopes at full magnification.

 

[Dthomas3523]

The other scopes were ffp. The atacr reticle should line up the same as the ffp scopes at full magnification.

Unless there is an issue with your magnification ring is the point I’m trying to make.

 

[ShtrRdy]

I recently did a tall target test with a 2nd gen ATACR. I found that the distance between groups was VERY close to what was expected after dialing 9 mil. I also found that the power ring had to be slightly off the maximum position past 25x in order for the reticle to be scaled properly.
This was the point Dthomas3523 was making.