View Full Version : POI shift when using a 3x magnifier.
These things aren't supposed to change the zero of the optic but I've noticed a definite shift when using one. I'm using an Aimpoint Comp M3 and a Vortex 3x magnifier. If I zero the M3 without the magnifier I get about a 2 1/2 inch group where I expect at 100 yards. I flip the magnifier in place and the rounds land about 2 inches to the right and 1 inch low.
So I'm thinking maybe my eyes just aren't good enough to zero unmagnified. I zero the M3 with the magnifier in place. Then I shoot unmagnified. Same problem. The groups are consistently to the left. Flip back to the magnifier and the groups are dead on.
I'm shooting from the sitting position using sandbags and firing 10 shot groups. I can repeat this magnifier POA/POI shift consistently.
So I'm wondering:
1) Do magnifiers actually shift the POI despite what the glossy brochure claims?
2) Is this problem because I'm using a crap magnifier? I'm ok with that. My magnifier is just for range time fun.
3) Is this a symptom of the astigmatism I have in my shooting eye?
1) Yes
2) No
3) No
I am thumb dancing on a tiny keyboard right now so I won't go into the full explanation. But it has to do with centering the red dot within the magnifier itself.
I'm pretty sure this is where you see the difference between a $500 piece of glass made for a specific optic on an equally thought out mount and...well...other stuff. At least you have the right attitude of "range fun time" so I'd leave it at that.
I haven't noticed a poi shift with my aimpoint magnifier
I'm pretty sure this is where you see the difference between a $500 piece of glass made for a specific optic on an equally thought out mount and...well...other stuff. At least you have the right attitude of "range fun time" so I'd leave it at that.
I haven't noticed a poi shift with my aimpoint magnifier
What I suspected - you get what you pay for. I just don't know if I find a magnifier useful enough to lay down $600 bucks. My ACOG seems to work better as a medium range optic than an aimpoint/magnifier combo. Thanks for the info. I was hoping someone with a real magnifier would chime in.
http://en.wikipedia.org/wiki/Parallax
Maybe the magnifier is mounted too far from the dot sight?
http://en.wikipedia.org/wiki/Parallax
Maybe the magnifier is mounted too far from the dot sight?
The magnifier is mounted as close to the aimpoint as possible. With the aimpoint's rear cover closed, I cannot flip the magnifier into place. I think this is just the quirks of a cheap magnifier.
From what you said in your last post I'd sell the magnifier if I were in your position. Don't even worry about replacing it. You're shooting good groups without it. You have an ACOG already. Take it as a sign and remove some dead weight from your rifle. I have a hard time trying to figure out why people spend soooo much money trying to get a red dot or reflex sight to do something they weren't designed for.
From what you said in your last post I'd sell the magnifier if I were in your position. Don't even worry about replacing it. You're shooting good groups without it. You have an ACOG already. Take it as a sign and remove some dead weight from your rifle. I have a hard time trying to figure out why people spend soooo much money trying to get a red dot or reflex sight to do something they weren't designed for.
This was more of a tinkering thing. Trying out different stuff to see if I like it. I do agree on the weight. It adds a noticeable amount vs the Aimpoint alone.
Just a small update. I contacted Vortex about this and they told me the magnifier should not be introducing any parallax error and that it might be my eyes perceiving the dot differently under magnification. They offered, even though I didn't ask, to look the magnifier over just in case it was bad. +1 for their customer service.
So I went to the range today and decided to test their theory. I re-zeroed the aimpoint without magnification and confirmed my POA/POI was the same. I then used the magnifier but shot left handed/left eyed. There was no POI shift. The group was a bit larger (I attribute that to shooting left handed) but the group centers lined up nicely.
I then switched back to the right and there was an unmistakeable POI shift. It's my crappy eye sight. I don't know if using better glass would help alleviate the issue but I'm not willing to find out. I've decided a magnifier isn't for me.
Cylinder Head
07-22-2012, 19:04
I'm using an Aimpoint 3xmag with my CompM3 and have not noticed any shift. Glad to hear it wasn't the equipment, sorry to hear it was your vision.
I forgot to comment back on this thread. Let me be clear a magnifier can and will absolutely cause POI shift if the red dot is not centered within the magnifier.
When this question was originally asked I was actually out with Travis Haley working that exact issue. We tested with an Aimpoint 3x and an Eotech 3x and both introduced subtle POI shifts. We could make the shift go left, right, up or down at will by simply adjusting the retaining screws that attach the mount to the magnifier.
When we got the red dot to the exact center of the magnifier the POI shift stopped - but the slightest bit out of center was noticeable, repeatable and predictable.
This was done with both a T1 and a PRO. I suspect it will be the same for EOTechs but haven't had a chance to go out and test yet.
Anything that changes the perceived location of the sights , open or optical , will give a POA/POI shift . Some examples , light conditions , mirage , eyesight , parralax , etc. can and will cause a shift .
SuperiorDG
07-23-2012, 16:01
I forgot to comment back on this thread. Let me be clear a magnifier can and will absolutely cause POI shift if the red dot is not centered within the magnifier.
When this question was originally asked I was actually out with Travis Haley working that exact issue. We tested with an Aimpoint 3x and an Eotech 3x and both introduced subtle POI shifts. We could make the shift go left, right, up or down at will by simply adjusting the retaining screws that attach the mount to the magnifier.
When we got the red dot to the exact center of the magnifier the POI shift stopped - but the slightest bit out of center was noticeable, repeatable and predictable.
This was done with both a T1 and a PRO. I suspect it will be the same for EOTechs but haven't had a chance to go out and test yet.
This^^^
Thanks for not making me type that out.
I forgot to comment back on this thread. Let me be clear a magnifier can and will absolutely cause POI shift if the red dot is not centered within the magnifier.
Understood. I have the dot centered in the magnifier, at least what my eye tells me is centered =) I probably could play with the magnifier adjustments and compensate for for the POI shift, but it's just not worth the effort. I've played with the setup enough to realize it's not for me.
I had to adjust my aimpoint 3x slightly to get proper poa/poi. That said, I'd rather have an Acog, mostly due to the ghost dots I see with the M2. I shoot much better with the acog. Although I did whack a chippy first shot @40yds with a friends eotech on a 6.5" FA AR. :D
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