Co-Witnessing Sights Issue

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dragon011

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Hello,

I hope to find a solution here for the issue I encountered last Saturday at the range. I recently bought M&P Sport and Vortex Spitfire 1x prism scope. After I sighted in my iron sights I proceeded to zero in my scope. After I completed this i noticed that not just they are not co-witnessing (it should be lower 1/3) but that these two zeroes are off by ALOT! I understand that user error is possible when sighting in iron sights, but we are talking here by at least 25 inches (50 MOA) difference (the center of the scope to the right from the front sight) at 50 yards (if I am measuring this correctly). How is this possible when rounds were hitting at the center area when I zeroed them separately? I would appreciate your help since I tried to find similar issues on the net without any success. I even contacted Vortex but they suggested to send the scope back for inspection. I would appreciate your input. Thank you.
 
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today I zeroed my M&P15 and the SPARC2. I started at 25yds with the irons sights until it was in there. I read you should zero at 50yrds overall cuz of the trajectory of the bullet blahblah....so I correct the irons at 50yds. BTW, right out of the box the irons shot LOW so I had to adjust elevation....

I then turned on the SPARC2 and aligned the dot for windage. and if would have known I would have just adjust the red dot so when looking through the irons, the red dot eclipces the front top of the front sight.

I folded the rear sight down, the red dot should now be roughly in the middle , both eyes open at your target...

You want your red mounted as far forward as you can, at least 4" from your eye.

The height of my red dot i think has to be at 40mm to 1/3 co-wit.

You should read your directons for further details....

hope this helps...let us know....
 
If the irons are already zeroed to your satisfaction, look through the rear sight aperture correctly with front sight post tip centered. Adjust the optic accordingly to the tip of front sight post. This will provide same zero for both irons/optic. Now if that Vortex has a lot of parallax it will be sensitive to consistent cheek weld.
 
Thank you for your replies. Here is some more info...The scope came with the base that should do lower 1/3 co-witness. I zeroed in my irons at 50 yds before putting on the scope. When i zeroed in the scope at 50 yds and looked at co-witness pic the center of the scope was to the right from my front site by alot. Now... i understand that i could just bring the center of the scope to co-witness as they should... but that would probably get me off the paper because of almost 50 MOA difference.

I was thinking about it some more and what i concluded is either the scope is deffective or i screwed up by just tightening the base screw with my fingers since i didnt have a wrench. It seemed tight and the scope was not moving ...but under the recoil... it is possible...Could this actually cause this huge discrepancy between two zeroes?
 
dragon011 said:
Thank you for your replies. Here is some more info...The scope came with the base that should do lower 1/3 co-witness. I zeroed in my irons at 50 yds before putting on the scope. When i zeroed in the scope at 50 yds and looked at co-witness pic the center of the scope was to the right from my front site by alot. Now... i understand that i could just bring the center of the scope to co-witness as they should... but that would probably get me off the paper because of almost 50 MOA difference.

I was thinking about it some more and what i concluded is either the scope is deffective or i screwed up by just tightening the base screw with my fingers since i didnt have a wrench. It seemed tight and the scope was not moving ...but under the recoil... it is possible...Could this actually cause this huge discrepancy between two zeroes?
Click to expand...

Forget about lower 1/3. Doesn't matter.

The optic reticle will be left, right, above and all over the map in relation to the front sight post (and that's fine) unless you are looking through the rear sight aperture with the front sight post centered. Otherwise, when you move your head around the optic and front sight post will not be aligned. However, the optic reticle will remain on target even though you move your head around and the front sight post moves off. Try it.

And yes, the optic needs to be properly mounted and tightened. Probably be a good idea to start there, ya think?
 
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yeah ...what he said...the primary thing is to get your iron sights zeroed as these are the basis for backup sights....then simply look through your scope/red dot thingy and adjust windage and elevation so the red dot is front sight post centered. FIRE for effect and then adjust.......i think it's that simple- i did it 12 hours ago.
ChattanoogaPhil said:
Forget about lower 1/3. Doesn't matter.

The optic reticle will be left, right, above and all over the map in relation to the front sight post (and that's fine) unless you are looking through the rear sight aperture with the front sight post centered. Otherwise, when you move your head around the optic and front sight post will not be aligned. However, the optic reticle will remain on target even though you move your head around and the front sight post moves off. Try it.

And yes, the optic needs to be properly mounted and tightened. Probably be a good idea to start there, ya think?
Click to expand...
 
I agree it should be that simple. However, this discrepancy is present when i look through my rear sight and that is the actual problem. I think i will remount the scope and tighten it with torque wrench and re-zeroe it...to rule out or confirm that mounting was the cause of zero shift with the scope compared to my iron sight zero.

Thank you again for your help! I appreciate it!
 
TORQUE WRENCH: shirley , you jest!

There is something you are leaving out and not telliing us. You sound like you are zeroing both systems independent of each other then going back and looking through your sights ... I don't know what you are doing really-can't follow.

Vortex will tell you in the instructions how to install using what spacers for the desired absolute or the recommended 1/3 co-wit.

It will tell you bore sight and then shoot at 25 or 50yrds.

You then look through your sights and "dial" in the red dot ( provided yours is a red dot) until while looking through your iron sights the red dot sits right on the front post.

Shoot at the target and see where you are.....

your iron sights have to be your aiming point of reference for this-this way.....then you dial in your red dot.

what say you?
 
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ok...the scope is 1x prism type... yes... i am zeroing both separately which means they should be fairly close when both are zeroed not off by 50 MOA to the right...Right out of the box it comes with 1/3 lower cowitness mount.
Initially... when i zeroed in my irons i did what you suggested and just dialed in the center of the scope to cowitness and was off paper! So had to look through the bore to get it back on paper.
From all the above comments this process shouljd be easy...so i will bet that mounting was not properly done. Thanks again!
 
Co witness of sites doesn't mean that the red dot will absolutely sit atop the front sight every time. This is especially true if you have your irons zeroed for different distances. The sights should be zeroed independently, as they are meant to be used independently.

Here is the process I use.

1. Zero the irons... what ever zero you like to use with irons.

2. Mount the red dot, insuring that it is solid and does not move. Absolute co-witness, or lower 1/3, your choice.

3. With your iron sights up, look through the sights and adjust the dot to sit on top of your front sight. If you are lower 1/3, ensure that your head is down looking through your sights, not over them. This is used in the same fashion as a bore sight.... will get me on paper.

4. Now use the red dot only to shoot at the range you would like to zero for. I suggest 50 yards. Adjust the red dot accordingly. It may or may not be perfectly centered on top of your front sight at this point, but it does not matter. If the POI = POA, then the red dot is zeroed correctly. Same for iron sights. You should not be using them both at the same time... they are independent sighting systems.
 
Thank you...i will take it to the range again and repeat the process...i agree with all your posts... but first thing i need to make sure that mounting was or wasn't an issue. I just bought the scope and took it out of the box at the time so had to finger tighten it...it seemed tight and scope was not moving... but again ... recoil might have moved POI compared to POA.
 
With the 1x "prismatic" it would be interesting if you could answer some questions after going to the range.

With the optic sighted at bullseys, move your head side to side and up and down while keeping the rifle still. Does the reticle stay exactly in the same place on target or does it appear to wander around slightly?

Does the front sight post still appear sharp as without the optic mounted or does it appear slightly distorted or fuzzy?

Turning the focus ring for the reticle, is there any change in focus down range or the front sight post become fuzzy or distorted?
 
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Zero is particularly important with an AR platform due to the sight over bore of a whopping 2.5in. If you zero at short distances like 25yds, that barrel is really pointing up in the air. You'll be about a half foot high at 100yds and still around 9in high at 250yds. A 50yd zero flattens out the trajectory quite a bit to 250yds, keeping within about 2in above and below line of sight.

Use the calculator to help decide which zero is best for yiur intended shooting. Be sure will to go into options and set the correct sight over bore. Ballistic Calculator GunData.org


My irons and red dot share the same zero. They are back-up iron sights, BUIS, not an alternative zero bullet path sighting system.
:D
 
ChattanoogaPhil said:
My irons and red dot share the same zero. They are back-up iron sights, BUIS, not an alternative zero bullet path sighting system.
:D
Click to expand...

My irons and red dot do not share the same zero, as my irons are adjustable for known distance shooting, in theory reducing the need for hold over past 200 yards.

In reality, my eye sight isn't what it was, so past 200 yds without magnification, the target is probably pretty safe from me.
 
cyphertext said:
In reality, my eye sight isn't what it was, so past 200 yds without magnification, the target is probably pretty safe from me.
Click to expand...

Same here. I count on my AR to be a 200yd offhand battle rifle and mount a 1x optic accordingly. Otherwise, I should have brought my .308.
 
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