View Full Version : Cowitness - a first for me.
Eurodriver
03-24-19, 19:48
I’ve read on here that sometimes irons and red dots cowitnessed will not align themselves together. I thought there was no mother****ing way this was possible.
Turns out it is.
https://i.imgur.com/Kz3K8Mc.jpg
How in the world? That steel is 300 yards away. The dot is off by about 4 MOA in windage at least. I am not too concerned with the elevation since they are zeroed at different distances but the windage is crazy.
How on earth is that even possible?
You got me, 1 moa maybe but 4 is wtf? Parallax possible but not 4moa. That has to be frustrating, because when the stars don't align, Im bothered. Im annoyed today when its hot as fck ( sorta) and my DOPE is off because the ammo got cooked.
PB
Eurodriver
03-24-19, 19:55
You got me, 1 moa maybe but 4 is wtf? Parallax possible but not 4moa. That has to be frustrating, because when the stars don't align, Im bothered. Im annoyed today when its hot as fck ( sorta) and my DOPE is off because the ammo got cooked.
PB
No clue man. I would turn the dot off and ring steel with irons all day. Turn it on and look over the fixed BUIS and ring steel all day.
Looking through the rear peep to the front sight with the dot on confused the hell out of me. If I focused on the front sight, I hit the steel. If I put the dot on the target. I hit the steel. I knew I shouldn’t have dated that Vicky Vallencourt lookalike.
grizzlyblake
03-24-19, 20:12
Wtf. That makes no sense.
No clue man. I would turn the dot off and ring steel with irons all day. Turn it on and look over the fixed BUIS and ring steel all day.
Looking through the rear peep to the front sight with the dot on confused the hell out of me. If I focused on the front sight, I hit the steel. If I put the dot on the target. I hit the steel. I knew I shouldn’t have dated that Vicky Vallencourt lookalike.
Vicky is your girl, good for you. That is quite puzzling, I mean crazy interesting , I look forward to hearing those that can explain.
Ive never seen it in many rifles.
PB
Your head has to be in the same position behind the optic it was when the carbine was zeroed when making precision shots.
Dr. Bullseye
03-24-19, 23:01
Its parallax or some other optical reason. I noticed the same thing but just ignored it and everything was fine for both red dot and irons.
grizzlyblake
03-25-19, 07:34
What RDS is that?
Eurodriver
03-25-19, 08:11
What RDS is that?
T1 2 MOA
The irons and the AP are probably mounted ever so slight out of line on the rifle. Maybe tolerance stacking. In other words the receiver pic rail isn't in perfect alignment with the irons, maybe the irons are off center by a mil or two. You don't notice it when using the different sights individually since you're eye is so close to both and you can get a zero with both.
VortexOptics
03-25-19, 10:14
I’ve read on here that sometimes irons and red dots cowitnessed will not align themselves together. I thought there was no mother****ing way this was possible.
Turns out it is.
https://i.imgur.com/Kz3K8Mc.jpg
How in the world? That steel is 300 yards away. The dot is off by about 4 MOA in windage at least. I am not too concerned with the elevation since they are zeroed at different distances but the windage is crazy.
How on earth is that even possible?
Out of curiosity - why do you want the irons to match up with the red dot? Your irons and red dot are two totally different sighting devices. Just because you can see your irons through the red dot window doesn't mean they need to be used. If your red dot is sighted in and shooting accurately by itself then it's working exactly as it should. If the irons then are also sighted in and shooting accurately by themselves then they're working exactly as they should as well. The two systems were never designed to be used together at the same time. One is a primary and one is a backup if SHTF. If you have fixed irons and they don't match up then certainly that would be annoying as far as someone's own OCD goes, but if both work fine independently of one another, then you're in good shape.
Dr. Bullseye
03-25-19, 12:33
You do see some video reviews of red dots where the guy reviewing says something like --I really haven't zeroed the red dot, I just lolly-poped it on top of the FSP.
VortexOptics
03-25-19, 12:48
You do see some video reviews of red dots where the guy reviewing says something like --I really haven't zeroed the red dot, I just lolly-poped it on top of the FSP.
*Face Palm* - At that point they should just save themselves the money from buying a red dot and go irons only unless they're just really lucky. You can take a red dot that is nowhere near sighted in and just manipulate your face/eye enough to make the red dot appear to lolly-pop on top of the irons. At no point in simply moving your face and eye position around are you making the red dot any more or less sighted in (There is no effect on point of aim/impact with that). Red dots are sighted in to a certain spot regardless of where your eye position makes the red dot appear to be in the optic's field of view. Likewise, if you actually go to sight in the red dot with the turrets and just try to move the red dot around in the optic until it lines up with your irons, there's no guarantee that's going to be anywhere near zeroed in. You might get it all perfectly lined up with your irons while looking through the sight, then move your head or eye a bit, and now it's not lined up anymore.
Bottom line - the red dot is a stand-alone aiming device that should be sighted in completely separately from any other secondary aiming device on the firearm. Same goes for the irons or any other secondary aiming device. Think of them separately, look at them separately, use them separately and if they both work the way they should when used by themselves, then they are working exactly right.
This is why Irons are set to an individual shooter, and why Iron Sight ARs don't make good "pool" weapons.
The same gun zeroed for one guy, won't have the same zero for another guy depending on how they're positioning their body/head on the gun. I've seen different POIs when switching from prone to sitting on my iron sight ARs.
Just one reason why I prefer lower 1/3 over absolute cowitness
Eurodriver
03-25-19, 18:10
Just one reason why I prefer lower 1/3 over absolute cowitness
Ditto. I’d be annoyed if I had to look through the sites all the time.
Out of curiosity - why do you want the irons to match up with the red dot?
I don’t.
Coal Dragger
03-25-19, 19:20
Is this a free float rail mounted front sight or a barrel mounted front sight?
My SR-15 has a fair amount of left windage on the rear iron sight to get zero at 50/200 yards, but the Nightforce 1-4X24 on the upper receiver required very little windage to zero. So the rail is off centerline ever so slightly near the muzzle, probably just a bit of tolerance stacking between the upper, rail timing shims, barrel extension, and rail. I still have windage left over on the rear and it zero’d so I’m not overly concerned.
I would venture a guess that if I slapped an RDS on top there would be a similar variance to your photo.
Just one reason why I prefer lower 1/3 over absolute cowitness this.... OCD would kill me, if they weren't perfect
Zero the windage on the RDS at 300 yards.
Eurodriver
03-26-19, 05:16
Is this a free float rail mounted front sight or a barrel mounted front sight?
My SR-15 has a fair amount of left windage on the rear iron sight to get zero at 50/200 yards, but the Nightforce 1-4X24 on the upper receiver required very little windage to zero. So the rail is off centerline ever so slightly near the muzzle, probably just a bit of tolerance stacking between the upper, rail timing shims, barrel extension, and rail. I still have windage left over on the rear and it zero’d so I’m not overly concerned.
I would venture a guess that if I slapped an RDS on top there would be a similar variance to your photo.
It’s a barrel mounted FSB.
Zero the windage on the RDS at 300 yards.
I can’t tell if you’re serious. In case you are, this has a 10.5” barrel and there’s always a 6+ mph wind.
Not unusual IME.
When I dial in RD and BUIS I’ll dial irons in first and adjust dot dead center L/R and just into FS blade.
This gets me real close with RD, but seldom, if ever dead nuts “on”.
Fine tuning is necessary to have the dot “on”.
I attribute this to tolerances with rail/mount.
voiceofreason
03-26-19, 14:37
I use 1/3 co-witness, mine are never right on top of each other.
Likely because I run them with a different cheek weld. Pressed into the stock running irons, more "heads up" running an RDS.
Zeroed for how I run them, they're not exactly on top of each other. No biggie as they are ZEROED and hit where they are supposed to.
I use 1/3 co-witness, mine are never right on top of each other.
Likely because I run them with a different cheek weld. Pressed into the stock running irons, more "heads up" running an RDS.
Zeroed for how I run them, they're not exactly on top of each other. No biggie as they are ZEROED and hit where they are supposed to.
THIS!!!
It’s a barrel mounted FSB.
I can’t tell if you’re serious. In case you are, this has a 10.5” barrel and there’s always a 6+ mph wind.
I'm serious. I frequently shoot handguns at 100 meters, so zeroing the windage on a RDS at 300 yards with a 10.5" carbine is not far fetched. If your no wind windage zero is on at 300 yards, everything at closer ranges will look good. You are not sacrificing iron sight plane length with a shorter barrel and a RDS.
The way I have my 16" carbines zeroed, I hold the base of the red dot at the base of the neck on a silhouette at 300 yards and the rounds drop into the middle of the torso. The carbines have Aimpoints with 4 moa dots that are set up for lower 1/3 co-witness.
I just ordered my first 1/3 co witness mount from Scalarworks. Im thinking I will like it.
Doc Safari
04-08-19, 17:14
I went through this years ago, and it bugs me too.
Sample of one brand, but several rifles, all BCM. I sort of wish I'd kept my fixed backup sights long enough to see what happens with a Colt carbine.
The rear backup sight that seemed to allow perfect alignment over the dot on any rifle was the LaRue LT103. DD 1.5's didn't do it, neither did "chopped carry handle" LMT backup sights. IIRC the MagPul folding MBUS did it on some rifles and not others.
This is one reason I only use the front sight for reference now. I use a folding BUIS at the rear and when I shoot I try to center the dot over the front sight post as much as possible. The rear MBUS stays folded, as in DOWN.
A worse thing is to zero your rifle with the rear sight folded, then deploy the rear sight and find the dot isn't in the same place in the optic's window as it is without the rear sight. This gets back to the RDS parallax issue since when co-witnessing at 1/3 you're forcing the red dot into the lower part of the lense.
That's when I said, "Eff it" and just started using the front sight for reference.
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