cowitness and lower 1/3 co witness

[Hackman]

I have a sight mark red dot and flip up iron sights and the iron sights seem to line up perfectly with the red dot at the top of the front sight. I want to get a vortex strikefire which advertises lower 1/3 cowitness. My sight mark mount looks to be even taller than the vortex mount so how does that work? Wouldn't the shorter vortex mount make the irons go in the upper 1/3 of the optic. I'm like wtf. Here's the current setup

(http://s1370.photobucket.com/user/Dano1987/media/20150726_231954_zpsrghml9yt.jpg.html)
http://i1370.photobucket.com/albums/ag273/Dano1987/20150726_231954_zpsrghml9yt.jpg (http://s1370.photobucket.com/user/Dano1987/media/20150726_231954_zpsrghml9yt.jpg.html)

[TheBelly]

cowitness and lower 1/3rd only mean how much of the viewable area of the optic is covered by the iron sights. Seeing as the red dot will follow the location of your eye (when parallax is removed), this is a physical attribute and is independent of the actual dot itself.

cowitness (aka: absolute cowitness) is when the iron sights take up the center of the optic.

lower 1/3rd is when the irons take up the lower 1/3rd of the optic.


The concept is that it's easier to view the dot when there aren't a big set of irons in the way.

[SideShow Bob]

You mount the red dot,( after you have satisfactorily sighted the iron sights in ) if you are using a tall mount,for a Lower 1/3 co-witness, turn on your red dot, flip up your iron sights and look through them and get a good sight picture through the irons. Then slowly adjust the dot to sit on top of the front sight post while holding the good sight picture on the irons. This is referred to as a " Pumpkin on a Post ".
Now shoot a few rounds at a target using the dot on the optics. You may need a tiny bit of adjustment, but should be pretty much on target.
and Ta Da, your red dot is sighted in at lower 1/3 co-witness.

[brutal]

You mount the red dot,( after you have satisfactorily sighted the iron sights in ) if you are using a tall mount,for a Lower 1/3 co-witness, turn on your red dot, flip up your iron sights and look through them and get a good sight picture through the irons. Then slowly adjust the dot to sit on top of the front sight post while holding the good sight picture on the irons. This is referred to as a " Pumpkin on a Post ".
Now shoot a few rounds at a target using the dot on the optics. You may need a tiny bit of adjustment, but should be pretty much on target.
and Ta Da, your red dot is sighted in at lower 1/3 co-witness.

Lolipop setup for a red dot only works with absolute co-witness, not lower 1/3.

[brutal]

You mount the red dot,( after you have satisfactorily sighted the iron sights in ) if you are using a tall mount,for a Lower 1/3 co-witness, turn on your red dot, flip up your iron sights and look through them and get a good sight picture through the irons. Then slowly adjust the dot to sit on top of the front sight post while holding the good sight picture on the irons. This is referred to as a " Pumpkin on a Post ".
Now shoot a few rounds at a target using the dot on the optics. You may need a tiny bit of adjustment, but should be pretty much on target.
and Ta Da, your red dot is sighted in at lower 1/3 co-witness.

To be clear, one must look through the iron sights to lolipop setup a red dot initial zero.

Here's a bit of reference for you, something I put together as I agonized over factory Aimpoint mounts vs Larue mounts.
https://www.ar-15.co/attachment.php?attachmentid=59886&d=1438050494

[Hackman]

You mount the red dot,( after you have satisfactorily sighted the iron sights in ) if you are using a tall mount,for a Lower 1/3 co-witness, turn on your red dot, flip up your iron sights and look through them and get a good sight picture through the irons. Then slowly adjust the dot to sit on top of the front sight post while holding the good sight picture on the irons. This is referred to as a " Pumpkin on a Post ".
Now shoot a few rounds at a target using the dot on the optics. You may need a tiny bit of adjustment, but should be pretty much on target.
and Ta Da, your red dot is sighted in at lower 1/3 co-witness.

With the red dot sighted in, I look through the irons and I have pumpkin on a post. The red dot sits right on top of the front sight post. That's why I thought it was absolute co witness. Sight mark says it's lower 1/3 co witness and so does vortex but looking at pics, they may be the same height. So how is it that I get the pumpkin on post when looking thru iron sights?

[SideShow Bob]

What is the RD mount height ?

And according to Brutal, I am talking out my Arse on this,
Brutal you hurt my little feelers, I'm going to report you to the Mods ! [Tooth]

And I possibly could be, this setup for me has worked great with my EoTechs before everything was lost in the "Great Floods of 2013.......

Go shoot your setup and see how it does, if it works good, don't fix what ain't broken......

[mutt]

Lolipop setup for a red dot only works with absolute co-witness, not lower 1/3.

Huh? Explain? As SideShow Bob posted, this is exactly how all my lower 1/3rd co-witness sights get roughly zeroed. Then I flip the rear down and do my fine tuning of the red dot's zero. When I flip the rear up again and look through it, the red dot sits right on top of the front sight post. How is this not correct or workable? I've used this method on T1's, Comp M2/M3's. Eotechs and knockoff PA sights. They all zero the same and exhibit the same visual appearance. And I've confirmed the irons and the red dot have the same POA/POI. If I am doing it wrong, I'd like to know.

[Hackman]

I just wish I could understand this. The sights are definitely in the very middle of the optic. So how is that 1/3?

[Hackman]

I am so frustrated. How could this be lower 1/3 co witness with the sights and red dot right in the very center?

[mutt]

All absolute and lower 1/3rd really means is the height of your optic mount. Some people, especially those with a fixed front sights, like a less cluttered FOV so they opt for a higher optic mount. This places the front sight post in the lower 1/3rd of the optic's tube. Some people like the center of their optic tube to be exactly where their irons are. Those are absolute cowitness and the front sight post will appear in the center of the tube. For those with flip down fronts (like you) it's just a matter of preference on how high you want your optic. Example (the left is absolute cowitness):


http://www.laruetactical.com/sites/default/files/t-1sightpicture-wtarget_0.jpg

If you were to look through your irons on the lower 1/3rd, your dot would appear inside your rear aperture and be superimposed over the tip of your front sight post (assuming they were zeroed at the same distance as your RDS).

[kidicarus13]

http://images.tapatalk-cdn.com/15/07/27/a73c613881495bd1a09d79d77f35c5bc.jpg

[brutal]

Well, some of you caught me mid-edit.

Because the red dot is holographic, any time you can see the (zeroed) dot on POA, it's on. That doesn't mean it's going to be lolipop on the FSP.

BlasterBob was right to begin with and I corrected my post after I reread what I typed. As long as you look through the rear irons and lolipop the red dot, it doesn't mean crapola if it's absolute or 1/3 lower co-witness, if you see it on the FSP, it's good for a rough zero.

This image probably does the best job showing all the options. Basically what you will see depends on whether you are looking through the rear sight or not...

http://www.rangerproof.com/wp-content/uploads/2015/05/cowitnessdiagrams-1.jpg

See, that's what happens when other post on you mid-edit. hahah.

[mutt]

Well, some of you caught me mid-edit.

OK. Universe makes sense again [Beer]

[Hackman]

Please see photograph again. Does it look like the sights are aligned with the center of the optic? Did my lgs sell me some weird extra tall sights? Are the optic manufacturers jacking with me??

http://i1370.photobucket.com/albums/ag273/Dano1987/20150726_231954_zpsrghml9yt.jpg (http://s1370.photobucket.com/user/Dano1987/media/20150726_231954_zpsrghml9yt.jpg.html)

[Hackman]

I just realized how ridiculous that gas block looks. It wasn't cheap either.

[mutt]

Flip up your sights and turn off your RDS. Look through your irons. If they fall below the centerline of the tube, the mount is lower 1/3rd. If they are in the middle, mount height is absolute.

[Hoser]

Two things.

1. Take off those silly back up sights.

2. Get your scope sighted in and leave things alone. Go to the range and shoot.

[Great-Kazoo]

Two things.

1. Take off those silly back up sights.

2. Get your scope sighted in and leave things alone. Go to the range and shoot.

Once he has the dot aligned with his iron sights. Based on his other thread, he will end up starting all over not having a clue why the rounds are not hitting the target.

What the OP really needs is to
#1 stop over thinking this

#2 get someone to go out (besides ML) who already assisted. Bringing their rifle with RD & buis so he can see how one that's on paper / sighted in is

#3 FORGET how it looks cosmetically OP. Which IMO is what you're doing. You're thinking physically how 1/3 co-witness looks instead of how it works mechanically.

#4 ask the mods to close one or the other of your threads . it will eliminate some of the obvious confusion you're having.

[SideShow Bob]

I am so frustrated. How could this be lower 1/3 co witness with the sights and red dot right in the very center?

It's not, you must have the shorter mount, so you have absolute co-witness. Lower 1/3 would be a taller mount to where your iron sights line up in the lower 1/3 of the optic.

[Mick-Boy]

Hoser and The Great Kazoo speak good sense. This isn't rocket surgery. Don't over complicate it. For god's sake get someone familar with the AR to take you out to the range a couple of times. Multiple people explaining physical processes online leads to more confusion than it solves. Go to the range, zero the optic, stop messing with it, shoot.

[Joe_K]

Damn double post...must... have... coffee.

[Joe_K]

#2 get someone to go out (besides ML) who already assisted. Bringing their rifle with RD & buis so he can see how one that's on paper / sighted in is


I didn't really have time to help him as I was in the middle of setting up for a handgun class. I also didn't have my AR with me that day to show him what a lower 1/3rd looks like. Next time your out at the range give me a heads up Hackman and I can work with you.

Sent from my SM-G920T using Tapatalk

[Great-Kazoo]

I didn't really have time to help him as I was in the middle of setting up for a handgun class. I also didn't have my AR with me that day to show him what a lower 1/3rd looks like. Next time your out at the range give me a heads up Hackman and I can work with you.

Sent from my SM-G920T using Tapatalk

That's what i was referencing. You having to work and not actually dedicate a lot of time to help the op.

[Joe_K]

Gotcha.

Sent from my SM-G920T using Tapatalk

[Delfuego]

For god's sake get someone familar with the AR to take you out to the range a couple of times. This is great advice. Mick knows his stuff.

You may look into going to the Bristlecone Range if you don't have have a friend with skills. RW is an instructor there and could sort you out quickly and competently. I have seen him (and helped him) sight in many rifles over the years.