Pistol Red Dot POA/POI shift with different shooters?

[wally]

This is too weird for me to understand, so I'd like to know if anyone else has ever ran into this.

Presbyopia marches on, so my wife finally decided it was time for Red Dot on her Buckmark. She'd had great results with the optics on my S&W M22, Neos, and Ruger MkII.

Picked up a Primary Arms MD-FBGII red dot on my way to the range (they are local) for the small size and nice price. Mounted it, and it was dead nuts on at the plate rack.

Finally cooled off enough for my wife to come along with me and she couldn't hit anything with the new red dot, she was ready to have me "just get rid of it!" when I had her try my S&W M22A, she was nailing the plates with it. I tried her Buckmark and found it was still dead nuts on. She was still way off. I then saw she was hitting about 15" low at 10 yards

I adjusted the sight to raise the POI about 14" (not a lot of adjustment left) and she started nailing the plates, I couldn't hit anything with it after the adjustments.

I've introduced a fair amount of shooters to their first red dot experience and once they grok that you need to focus on the target and "look thru the dot" none has ever required any dot adjustments to hit the plates with guns I'd zeroed.

Anyone else ever run into this?

Why only one of four (more counting what is on my SBRs) red dots?

I could understand a left-right shift as possible parallax from the way the brain merges the red dot and the two eyes open image, but don't see a source for vertical parallax. My wife does have a vision defect in that she can not see 3-D effects or do binocular fusion, so she has to close one eye when using binoculars, but she has had no issues using various red dots on my SBRs and other pistols.

 

[F-111 John]

Is it possible that the problem red dot has a second, dimmer "ghost" dot if looked at from a slightly lower angle?

She may be sighting through the sight and picking up a dot reflection near the top of the field of view instead of the real dot in the center of the field of view.

Just guessin'

 

[GeoEmeritus]

Could she be looking at the dot with one eye and the target with the other?

 

[wally]

Is it possible that the problem red dot has a second, dimmer "ghost" dot if looked at from a slightly lower angle?

First thing I thought of, I couldn't see any "ghosts" when I looked both at the range and again when we got home. We swapped shooting positions in case it was some weird external source reflection, but it made no difference.

Could she be looking at the dot with one eye and the target with the other?

Her instinct is to close the left (dominate) eye since she is right handed, but things didn't improve when I explained to her to keep both eyes open. In any event left/right eye parallax is is left-right shift, not up-down.

The adjustment was pure elevation I never touched the windage.

This is a head scratcher, I wouldn't believe it if I didn't witness it. I'm looking forward to our next outing to see if she starts hitting ~14" high

 

[chicharrones]

How does her vision compare to yours?

I've moved to red dots when possible, too. Even with trifocals or progressive lenses, the dot is a bit blurry with my glasses unless I tilt my head back to the middle out of the three lenses. I have finally adapted to just shooting with the dot a bit blurry unless I need to attempt extreme precision.

When I go shooting with a good friend of mine, we both shoot to slightly different elevation points, but our windage is right on. We've determined this mostly to be how we use the dot for aiming. We both like cover hold for defensive style shooting, but when we are shooting for groups with non-self defense style guns, I prefer 6 O'clock hold vs. his cover hold.

His eyes are better than mine and cover hold works well with a red dot for precision aiming for him. With my eyes, seeing a distorted dot, I have to use the 6 O'clock hold for precision aiming. It still beats trying to see open sights, as my eyes can't work with those at all unless I use the reading portion of my glasses.

 

[earplug]

Yes.

I have a Match Dot mounted on several 22 Pistols. Depending on if I shoot one handed for Bulls-eye or two handed for other games the POI moves.
Its a function of recoil and grip. And a shooter who constantly pushes the trigger sideways will have a different POI then a shooter who manages a perfect trigger.
The NRA had a article on shooting lightweight rifles and accuracy caused by the recoil change.

 

[GeoEmeritus]

Plus 1

That would also explain the difference between the Smith and the Buckmark.

 

[wally]

That would also explain the difference between the Smith and the Buckmark.

How do you figure?

She was shooting the S&W and the MkII to the same POA/POI as I was. While she is not the best shooter, no way is she jerking the trigger consistently enough to shoot ~2" groups at 10 yards ~15" low. I had her put the dot on the top of the plate and the impacts were then at the bottom of the rail covering the reset mechanics in about a 2" group. When I moved the dot to match her point of impact from the top of the plate hold, she was nailing the plates with a center hold and then did as well with the Buckmark as the other two.

Before I added the Red Dot she had far more rounds thru the Buckmark than any other pistol. She shot the irons to the same POA/POI as I did (I need reading glasses to use irons effectively, she has only recently got to that point).

We see next time out, If its some kind of grip or trigger pull issue I don't see how it could possibly be very consistent for an infrequent shooter (I average about twice a week, she averages about once every six weeks, with maybe once in 16 weeks during our hot summer months).

 

[exbrit49]

possible prism vision

Do you or your wife wear prescription glasses? I do and I have what is known as prism vision. It causes the light to bend as it passes through the eye and
the light falls on an off center position on the back of the eye.
I do have prism vision and as I shoot with my left eye only the left lens is corrected for prism vision and I am able to see the target better and in the same place as everyone else. Without correction I get the same shift you are seeing.
If you are due for an eye test soon , specifically ask them to check for prism vision.

 

[wally]

Do you or your wife wear prescription glasses? I do and I have what is known as prism vision.

How would you explain the fact that her POA/POI was fine (same as mine, I did the zeroing) with two other red dot equipped pistols today, and with several other pistols and rifles in the past.

As to vision problems, she was legally blind uncorrected (probably why she married me ), and had PRK surgery in both eyes about seven years ago when she was running up against the limits of the correction available with contact lenses. At our last exam she was 20/25 in one eye 30/30 in the other. The issue is presbyopia (old eyes) -- the near point of vision has moved out making things inside of about 4 ft just a blur. Red Dots are the cure because you focus on the distant target and look "thru" the dot.

I might have just assumed a defective red dot but it was dead nuts on for me until I adjusted it for where she said she was placing the dot and where I saw the bullets impacting (low). Then she was nailing the plates and I was way high.

Speculation can be fun, but I want to hear if anyone else has ever experienced this. Its way beyond sight picture differences like preferring a "bullseye hold" to a "combat hold".

 

[gbran]

I've had red dots and bad eyes for years, but what you describe, is inexplicable to me.

 

[230RN]

1. All guns recoil slightly before the bullet leaves the muzzle.

2, Handguns, being relatively light compared to their missiles, recoil more noticeably before bullet exit.

3. Therefore, slight variations in how they are held (or who's holding them or what's mounted on them) can significantly affect group placement.

4. This may well explain everything.

Terry, 230RN

REF:
Hatcher's Notebook, "The theory of recoil," pp 290 ff. esp. page 295 ff.

 

[wally]

Hitting ~14" low at ten yards is way out of "how you hold it" and the guns "recoil response" territory. This is flinch territory at best, and no-one flinches into consistent groups that are just low.

She often flinches shooting 9mm (especially un-suppressed) and there are no grouping of any of the flinched shots.


Its as inexplicable to me as it is to gbran, as I said, I wouldn't believe it if I didn't experience it.

 

[chicharrones]

I'd guess you would need a laser training device on the gun to see what's going on with the Buckmark vs. the other guns in her hands.

 

[yugorpk]

Astigmatism. Even a little will case that dot to be spread out and the point of impact to shift between two different shooters. I can't shoot with a red dot and expect to hit anything without my glasses on and I never wear them otherwise.

 

[wally]

Astigmatism. Even a little will case that dot to be spread out and the point of impact to shift between two different shooters.

If the issue was anything with her eyesight it'd happen on all the Red Dot equipped guns. There is no way these relatively small differences can account for ~14" at 10 yards -- about 140moa! (2.3 degrees!).

The shape of the dot doesn't matter as if you are focusing on it you are using it wrong. For slow fire precision shooting you want the smallest possible dot and a consistent alignment of how you look through the dot at the target -- bullseye shooting is "rigged" to use your eye-brain "vernier acuity" when aligning sights with the target, which is significantly better than 20/20.

But for speed shooting you want a large dot 4-9 moa typically for easy pickup, and as long as the apparent size of the dot is smaller than the target you are good to go -- assuming its zeroed correctly, if the dot is on the plate when the trigger breaks it'll be a hit. I often "throw" the shot starting the trigger press when the dot is still moving towards the target knowing by the time it breaks the dot will have moved onto the plate. If your recoil control is good you'll never lose sight of the dot. This is my weakness when I'm "hot" I never lose the dot, when I'm doing poorly I lose it somewhere along the way. With .22lr I can feel like Jerry Miculek hitting a third plate before the first has finished falling. Great fun!

 

[DaisyCutter]

Different shooters probably mash the trigger differently. Most likely the dot is being true, it's the shooter.

 

[wally]

Different shooters probably mash the trigger differently. Most likely the dot is being true, it's the shooter.

Have you ever seen anyone mash the trigger in to 2" groups at 10yards? This is the pistol she is most familiar with that had a red dot added.

She did fine with two other red dot equipped pistols using the same POA/POI as me. I'd set hers up same as mine as was expecting the same results as she had with them.

Please no more speculations or guesses.

I want to know if anyone else has ever seen this happen. We are not talking the half diameter of the "black" for a "bullesye" vs. "combat" hold, here its a difference that nearly ran out of adjustment range on the sight.

 

[DaisyCutter]

Have you ever seen anyone mash the trigger in to 2" groups at 10yards?

Yes. Simply changing the point of contact of my finger pad with the trigger can shift my group right or left. In fact, my Glock 22&27 require a different than my Glock 41&30S. I have to move the trigger closer to my finger joint to be on target with the 45sss otherwise they shoot right. I'm a lefty.

I provided an honest attempt at being helpful. It didn't merit a condescending snarky response.

 

[F-111 John]

Have you tried removing the offending red dot from your wife's Buckmark and replacing it with a red dot from one of your firearms that you say you both shoot POA/POI?

If the aiming shift persists with the new red dot on the same Buckmark, then it isn't the optic. If the aiming shift does not appear with the offending red dot on a firearm she previously shot just fine, then the problem isn't with the optic.

If the problem does follow the optic onto any gun it is mounted, then it's time to ask her exactly what she is doing to aim with the offending optic.

 

[wally]

Follow-up.

Went out again this morning, my Wife was nailing the plates with the Buckmark that I'd adjusted for her. Still shooting so high for me as to be unusable. Added a third red dot equipped pistol into the mix (Beretta Neos) and she was nailing the plates without adjustments -- shooting to the same POA/POI as with the other two we tried the first time (Ruger MkII, S&W M22A).

This is just too weird, but now she has a pistol that nobody else can hit with, kind of like the old Carnival mid-way guns

 

[gp911]

That would be one heckuva consistent flinch to group that well but hit that low! That Buckmark can win you guys some side money now, bet the other folks they can't hit within 6" of her group and take their cash all day long. That is quite the geometrical anomaly given that she shoots all those other guns to spec. Weird and wacky stuff.

 

[il.bill]

Have you tried removing the offending red dot from your wife's Buckmark and replacing it with a red dot from one of your firearms that you say you both shoot POA/POI?

If the aiming shift persists with the new red dot on the same Buckmark, then it isn't the optic. If the aiming shift does not appear with the offending red dot on a firearm she previously shot just fine, then the problem isn't with the optic.

...

This seems to be a simple diagnostic step if you really want to understand what is going on. If not, then fire away as it is as long as it works for her on her pistol.