Magnifier makes me shoot left?

[Rittmeister]

Hey folks. Sighting in an AR with new stuff. Anderson lower, Timney trigger, Palmetto 16" upper (not that that matters).

I was using a Primary Arms red-dot sight on a lower 1/3 cowitness mount for a while, with decent results. I was not using any magnification. I had previously tried a Burris 1-4x scope but did not like the weight, and felt that with the shooting I get to do (100 yards or less, more's the pity) an unmagnified sight would work well.

My need to tinker, coupled with a sale flyer, did me in. I am now trying a Holosun sight, also on a lower 1/3 mount, with a 3x magnifier on a matching mount. The Holosun has clearer glass and the reticle is a chevron rather than a dot, and I find that I like it very much. My plan is eventually to get a quick-detach mount for the magnifier, to keep the weight down when desired.

I zeroed the sight unmagnified for a regular 25/300yard zero, and had it pretty dead-on. However, every time I flip the magnifier into place I wind up shooting slightly to the left. This happens both offhand and from a rest.

I am pretty ignorant of magnified optics other than the scope on my .22. I understand eye relief and I know I am positioned properly; the magnifier also has parallax (I think?) adjustments to bring the image of the sight's reticle into the center of the magnifier, which I have done, but from my research this shouldn't affect the point of impact anyway.

Can anybody point me to a problem either with my shooting or with the magnifier itself? I do have an astigmatism in my right eye, and am forever cursed to wear either glasses or contacts, but this didn't affect my shooting with the red-dot alone and I don't' see much of the "smear" that other vision-corrected folks talk about so I don't think that's it... but I've been wrong before.

I will also say this - I have always done my best shooting with iron sights, even when they're just backup sights. I am not a fabulous rifle shot (especially when shooting for group size) but had no trouble hitting a 12-oz pop can at 100 yards with my other AR, standing offhand; it has always worn fixed iron sights. Thus I feel my "practical" accuracy is at least decent.

This magnifier issue has me stumped. Any input appreciated!

 

[Moparnut]

I have never used a magnifier, so this is purely a guess. Is it possible the magnifier is not square to the sight? Thus making move your head slightly, adjusting your hold and changing the poi? I have been thinking of getting a magnifier so I would like to see where this goes.

 

[Klint Beastwood]

the image leaving the optic to your eye might not be in the same relationship than if it weren't there.
that's why in some cheap scopes with variable power, you'll see a POI shift when you change magnification. the reticle hasn't changed, it's still mechanically zeroed. what changes is what your eye sees, and the optical image of the reticle relative to the target.

 

[Rittmeister]

I got back to the range today and zeroed WITH the magnifier at 25 yards. I then tried it at 50 yards, and while the group printed high (as expected ballistically) it was still centered.

What I didn't get to do much of is shoot again without the magnifier to verify zero unmagnified. Only about 10 rounds. They printed well but I want to mess with it more to be sure.

So, I apparently should have zeroed with the magnifier all along. This falls in line with those who say you should zero a variable scope at its highest magnification, I guess, and it's something I should have remembered from past research.

Re: Moparnut's comment, based on further research the magnifier shouldn't change the point of impact, since it's only magnifying the image of the red dot and isn't actually part of the sighting/zeroing mechanism. I think what happened before is that I zeroed unmagnified and got the shots where I wanted them but the magnifier "magnified" a problem I didn't see at that distance. I suspect that if I had shot further out (50-100 yards) without the magnifier, my POI would have been to the left, despite being centered at 25 yards.

Whenever I get this setup to a longer range I'll be curious to see what it does. I do have to say that so far I like this Holosun with the chevron reticle very much. The only change I'm considering is a QD mount for the magnifier; right now it flips to the side but I'd like to be able to remove it altogether to lighten the gun when desired.

 

[Moparnut]

I thought maybe when you flipped the magnifier into place you may have moving your head or adjusting your hold somehow. Thank you for responding to me. I am glad you found the issue. Btw... What kind of magnifier is it and how do you like it?

 

[Rittmeister]

It's the Primary Arms Long Eye Relief Gen IV 3x magnifier (whew, long name). Right now it's in Primary's flip-to-side mount that lines it up with a lower 1/3 cowitness red dot position. They now also have an "advanced" magnifier; it's smaller and lighter and also double the price of the Gen IV.

The magnifier is good in my opinion, but this is the first one I've ever owned, and the only other experience I have was with a buddy's Eotech w/magnifier setup about 7-8 years ago, which I did not care for (the reticle isn't for me). This one has clear glass and seems to magnify without distortion. So far so good, though as I said above I plan to find a QD mount for it at some point.

 

[MidRoad]

I had a primary arms red Dot and flip to the side magnifyer on my ar as well. I too have slight astigmatism and wear glasses . I got rid of mine and went with a 1-3 scope because when I used the red Dot alone it was clear and sharp, but when I flipped the magnifier behind it, I would get a very slight "double Dot" I could shoot it ok, but it still wasn't as percise as I'd like.