POI change with reticle focus adjustment ?

[TroyMN]

I posted this at another site, but it was already buried on page 2 with no real good first hand experience. I guess I am impatient.

I have seen this before with a el cheapo scope. I just got my $900 Vortex scope and you can see the reticle move 2 MOA while lightly pushing up down, right left..... on the eye piece. It does seem to self center back, but really, I do not want 1/4 MOA change in my zero.
What are your experience with wiggling the focus eye piece? Have you tried it ?
My Leupold VariX-iii has a locking nut on the eyepiece to lock it in place.
I have no plan to focus the reticle often, but it's ability to shift worries me.

Thanks
Troy

 

[NateHaler]

I think you should call Vortex and discuss your concerns with them. Their customer service is outstanding.

Why are you pushing down on the eyepiece? What would happen if you pushed down on the objective lens while peering through the scope? Does either event reflect what happens when you fire the rifle?

As you've suggested, but what needs to be reinforced, is that you set the reticle focus once. ONCE, people. Then your job is to determine whether the scope is repeatable and reliable after you make windage and elevation adjustments, and magnification adjustments if you have a variable scope, and to ensure you have corrected for parallax-induced error by adjusting the objective or the side parallax knob (assuming your scope has either).

Parallax adjustment is NOT what you do to get a sharp target (or reticle) image. Parallax adjustment ensures that your reticle and the target images are on the same optical plane, so they do not appear to move relative to each other when you move your eye behind the ocular lens.

Shoot the box test. (Google it, it's been discussed a gazillion times...) Then shoot groups (not pathetic 2 or 3 shot groups, but five shot groups) at different magnifications in your variable scope's range. If POI changes with mag, you have a problem. If the scope won't reliably return to zero in the box test, you have a problem. The ideal that POI might change if you torque the eyepiece is not a problem, IMO, and I wonder why in the heck you would even do that.

Regardless, call Vortex, and above all, shoot the rifle with the scope and get REAL data, rather than engaging in anxious speculation.

 

[BoydAllen]

To put this all in perspective, the Nightforce 15-55 variable prototype that Walt Berger won the Cactus warmup two gun with in Visalia, weekend before last, has a so called European eyepiece focus. These types of adjustments typically have a fast thread and position is maintained by spring tension, rather than a lock ring. He won decisively, against a field that featured a few world record holders. I would worry about something else.

 

[TroyMN]

Boyd
Thanks for your feedback. It sounds like there is a spring in the scope to hold the fast focus eyepiece in place. When focusing, it seemed to wiggle the reticle. That is why I pushed it up and down a little. If we found out one of our scope mounts moved when we pushed on it, we would not assume it is ok if we just don't push on it. After a high power rifle recoil I did not just want to hope it would go back/ stay in perfect alignment. A high dollar piece of precision equipment, was not expecting "play" however if that is designed in, and it works for others cool. My previous experience with this issue was at the range, my brother-in-law shot my 270 and he refocused it for him and change the point of impact 3 to 4 inches at 200 yards.

 

[BoydAllen]

....different issue. I believe that the lenses in his eyepiece are not collimated correctly, that one or more in the eyepiece are not perpendicular to the optical axis and/or properly centered. I would send it back to the manufacturer. Have you had the same problem with your scope? How is your rifle grouping?

 

[TroyMN]

When the grouping changed inches on my backup rifle ( the one brother-in-law) shot. In needed to look at and see if it was loose scope mount, parallax adjustment, or other causing the POI change. We know on this European focus piece the spring did not return the scope to zero. I noticed that the eye piece had play in it ( similar to my new scope) when I wiggled the eye piece the crosshairs change position on the target....... my solution to this cheap scope problem was a cut a spacer to fill the void between eyepiece and main tube. It worked! He was a novice shooter and was getting 9's maybe better at 1000. He did not keep score but when I looked at his target they where never in the white.
I have not shot my scope yet, no need to waste ammo if I can see questionable performance of my equipment at home. The rifle shoots .5 to .75 depending on all that stuff that goes right and wrong.