Cowitnessing questions

[benw315]

I'm going to build an AR-15 in a couple months when I get my profit sharing check so I've been doing some research and am wondering about cowitnessing. I'm leaning towards an Eotech 2.0 w/ 3x magnifier for my sights but may go aimpoint... But am undecided on getting a free float rail with flip up BUIS or go with the standard FSP. If i get flip ups I want absolute cowitness when flipped up (I would shoot with them down) but lower 1/3 if I go with FSP. So... that being the case... does anybody have side by side comparison pics of cowitnessing and not cowitnessing vs. the same target from a distance? I cannot find any on the internet. I'm also open to suggestions in this aspect of my build. Thanks!

Ben

[militarymoron]

have you read the 'explanation of co-witness' stickied thread at the top of this forum? lots of info there, which might answer your questions.

[lethal dose]

I like the dissy set up. Middy with an fsb pinned at rifle length with a rifle length hg and a lower 1/3 cowit.

[Meplat]

I say stick with the standard FSP. It's one less thing that won't break and you won't have to worry about. No screws to come loose, no mechanisms to wear out, it's just there.
I also advocate using a fixed rear sight for the same reasons, and using a lower third co-witness on your optic.
You get the best of both worlds, the ability to use your optic unobstructed, and the ability to still use your irons immediately.
Read the co-witnessing explanation sticky, it will help you understand.
I suggest using an Aimpoint over an EOTech, and I don't mean to step on anyone's toes, but I find EOTechs to be very "niche" optics. I'm still trying to figure out exactly what that niche is or exactly what the appeal is with EOTechs.

[lethal dose]

To go along with what meplat is saying... aimpoint truely is the finest optic out there if you're going with a 1x. To be honest, I think I'd go trij reflex over eotech... even knowing about the washout issues. Eotech's reliability has yet to be proven to where I'd buy one and battery life is subpar. Also- I agree with the fixed rear buis, too. It's there when you need it. Just some food for thought, bro. Good luck, keep us posted.

[benw315]

Thanks for the help so far... and yes, I have read through most of the explanation of cowitness thread. I think what I need to do is shoot a rifle both ways to know for sure, but figured why not ask people who know. Durability for the FSP wouldn't be my primary concern as I do not plan on beating the hell out of my rifle. The reason I have been leaning towards Eotech is that I've heard aimpoints don't work as well with a magnifier (I may be wrong) and i like the smaller MOA dots. Not that I'm trying to start a "which one is better" thread ha...

[Hmac]

I have both. Nothing wrong with either, but the FSP is just one less thing to break. I prefer lower third co-witness.

I have both Eotech and and Aimpoint Micro T-1. The T-1 is nice for its brightness knob, but I prefer the Eotech for its better reticle.

[lethal dose]

No problem with 2 m.o.a. aimpoints with mag.

[Meplat]

Thanks for the help so far... and yes, I have read through most of the explanation of cowitness thread. I think what I need to do is shoot a rifle both ways to know for sure, but figured why not ask people who know. Durability for the FSP wouldn't be my primary concern as I do not plan on beating the hell out of my rifle. The reason I have been leaning towards Eotech is that I've heard aimpoints don't work as well with a magnifier (I may be wrong) and i like the smaller MOA dots. Not that I'm trying to start a "which one is better" thread ha...
Here is a good picture to illustrate and help you get an idea of what it looks like looking down the optic on an absolute vs. lower third co-witness with irons.
https://www.m4carbine.net/picture.php?albumid=291&pictureid=1429
As for the EOTech and magnifier, I can't say with certainty as I haven't used one, but I'm generally not a fan of using a 1x optic and a magnifier. My opinion is that, and it might be unpopular, if you want or need magnification, you'd be better of getting a variable scope or a fixed magnification optic like an ACOG to begin with. It will cost roughly the same, and the difference in quality and performance of a dedicated optic like an ACOG will be miles ahead of a red dot and magnifier combo.
Just something to consider.

[Hmac]

I have an Eotech G23FTS 3x magnifier. It works very well with my Eotechs and 1 MOA dot, not so well with my T-1 as it magnifies the 4 MOA dot into a kind of misshapen blob.

[lethal dose]

Check out the trijicon Tr24. Gorgeous glass.

[Failure2Stop]

I have shot with both absolute cowitness and lower 1/3 cowitness. My initial exposure was absolute cowitness due to the mounts at the time for the Trijicon Reflex and carry-handle goose-necks for Aimpoints (M68/Comp M!) were only setup for absolute cowitness. Once I started trying out lower 1/3 cowitness 1X optics I became intimately aware of how much faster one can be, how much cleaner the sigth picture is, how much easier it is to apply hold-offs without a front sight post blocking parts of the target, and how much more of the target can be seen without the FSP in the way.

I was initially dubious about a fixed rear sight, thinking that I would constantly have it in my field of view and have to try to peek over it while shooting. Not so. The rear sight blurs out and all you are really aware of is the dot and target with the FSP just lingering at the bottom of your sight picture.

I really only use a flip-up rear on guns with magnifiers, though they do remove the slight blur of the rear from the bottom of the FOV when looking through the optic and the body of the optic can be used as a hasty ghostring if the shooter still has line of sight through the center of the optic. There is an application for dedicated 100 meters and under guns to have absolute cowitness with a folded down rear sight, but it still won't do anything for an obscured/fouled optic.

A front sight in the upright position is a prerequisite for a fighting gun in my opinon. In the event of an optic failure or destruction it is one less thing to have to mess with before being able to effectively employ the weapon at anything other than contact distance. Further, the front of the gun gets hot, and trying to flip up a hot front sight while someone is trying to kill you is an unnecessary layer of stress that I prefer to avoid.

[benw315]

Thanks again everybody! And Melpat, I have seen that picture before, I was just curious if anybody had pics of a target maybe 50 yards away with cowitnessing. Failure, that is some very good information, thank you.

[kmrtnsn]

I say stick with the standard FSP. It's one less thing that won't break and you won't have to worry about. No screws to come loose, no mechanisms to wear out, it's just there.
I also advocate using a fixed rear sight for the same reasons, and using a lower third co-witness on your optic.
You get the best of both worlds, the ability to use your optic unobstructed, and the ability to still use your irons immediately.
Read the co-witnessing explanation sticky, it will help you understand.
I suggest using an Aimpoint over an EOTech, and I don't mean to step on anyone's toes, but I find EOTechs to be very "niche" optics. I'm still trying to figure out exactly what that niche is or exactly what the appeal is with EOTechs.

I suggest you take a look at the Military Morons torture test of the Vltor clamp on folding FSB.

http://www.militarymorons.com/weapons/ar.optics2.html#torque

As for your comments on the Eotech, I completely agree. I would love nothing more than to remove the 552 from my issued carbine and replace it with an M4S.

[Hmac]

but I find EOTechs to be very "niche" optics. I'm still trying to figure out exactly what that niche is or exactly what the appeal is with EOTechs.

I've only shot my buddy's M4s, don't own one, but I do have a T-1 on my SBR. I prefer the Eotechs for the reticle, which I find significantly better for quicker acquisition, better both-eyes-open, and quicker compensation for height-over-bore at 25 yards or less. Personal opinion.

[Thomas M-4]

I have shot with both absolute cowitness and lower 1/3 cowitness. My initial exposure was absolute cowitness due to the mounts at the time for the Trijicon Reflex and carry-handle goose-necks for Aimpoints (M68/Comp M!) were only setup for absolute cowitness. Once I started trying out lower 1/3 cowitness 1X optics I became intimately aware of how much faster one can be, how much cleaner the sigth picture is, how much easier it is to apply hold-offs without a front sight post blocking parts of the target, and how much more of the target can be seen without the FSP in the way.

I was initially dubious about a fixed rear sight, thinking that I would constantly have it in my field of view and have to try to peek over it while shooting. Not so. The rear sight blurs out and all you are really aware of is the dot and target with the FSP just lingering at the bottom of your sight picture.

I really only use a flip-up rear on guns with magnifiers, though they do remove the slight blur of the rear from the bottom of the FOV when looking through the optic and the body of the optic can be used as a hasty ghostring if the shooter still has line of sight through the center of the optic. There is an application for dedicated 100 meters and under guns to have absolute cowitness with a folded down rear sight, but it still won't do anything for an obscured/fouled optic.

A front sight in the upright position is a prerequisite for a fighting gun in my opinon. In the event of an optic failure or destruction it is one less thing to have to mess with before being able to effectively employ the weapon at anything other than contact distance. Further, the front of the gun gets hot, and trying to flip up a hot front sight while someone is trying to kill you is an unnecessary layer of stress that I prefer to avoid.

Couldn't have said it better.
My personal set up is Aimpoint with m-68 larue mount with larue fixed BUIS the rear sight is completely out of the field of view with the lower 1/3 set up. And you have INSTANT USE of your Iron back-up sights.

[benw315]

The only problem with a fixed rear BUIS is that I plan on adding a 3x magnifier so I can switch from shooting near to far easily. That is also the only thing I have worries about with the Aimpoint T-1. I love the optic but I'm worried that the 4 MOA dot with the magnifier may not work as well at 100 yards and past for me as I got lasik done to my eyes recently so I have some slight astigmatism :(

[Hmac]

I can promise you that the Aimpoint T-1 won't work well with a 3x magnifier, certainly not as well as it works with any Eotech. As it turns out, the difference between a 1 MOA dot and a 4 MOA dot is pretty significant.

http://ic2.pbase.com/o6/60/230460/1/129054337.sgsBLKHv.noveskesbr2.jpg

[lethal dose]

The 2 m.o.a. aimpoints work quite well with magnification.

[Hmac]

The other thing I find occasionally annoying about the T-1 is that it sometimes gets some internal reflections under some lighting conditions, something I don't get on my Eotechs.

[Failure2Stop]

I have no problem with the T-1/3X magnifier combo and generally recommend it to those that only occasionally want magnification and don't need to reach out more than 300 meters.

[Hmac]

I agree, it works fine for occasional use at intermediate ranges. More than that and I'd go with an Eotech.

[benw315]

Doesn't the magnifier make the 4 MOA dot of a T1 seem more like a 12 MOA at 100 yards? I thought I read this before but a quick search hasn't turned up much. I want to be able to be precise at times and if a dot covers up 12 inches at 100 yards I don't know how easy that would be.

[Hmac]

Doesn't the magnifier make the 4 MOA dot of a T1 seem more like a 12 MOA at 100 yards? I thought I read this before but a quick search hasn't turned up much. I want to be able to be precise at times and if a dot covers up 12 inches at 100 yards I don't know how easy that would be.

It magnifies the dot ("blob" in the case of the T-1), but it also magnifies the target. The relative sizes are the same, I suspect.

The problem as I see it is that any shooter error is magnified at distance. You're only starting with 4 MOA max accuracy to begin with.

[Failure2Stop]

It magnifies the dot ("blob" in the case of the T-1), but it also magnifies the target. The relative sizes are the same, I suspect.

This is true. The magnifier magnifies every image that enters it by 3X, target and reticle, which means that the dot size in relation to target will remain constant as long as the magnifier is placed behind the optic (as it should be).



The problem as I see it is that any shooter error is magnified at distance. You're only starting with 4 MOA max accuracy to begin with.

Neither part of this is true.
Shooting error is not magnified by the optic. Some shooters may have an issue due to the ability to see more wobble of the dot since range is increased though the image appears to be larger, therefore at 30 meters you will be seeing 30 meters worth of wobble though the target will only appear to be 10 meters away. What happens when the trigger is pressed is between the shooter's skill and inherent precision ability of the weapon.

A 4 MOA dot is well caipable of sub-MOA precision as long as the target is larger than 4 MOA. Molon has a good post on this proving that the precision ability of a weapon is constant as long as the shooter can provide a consistent hold.

[Hmac]

Shooting error is not magnified by the optic. Some shooters may have an issue due to the ability to see more wobble of the dot since range is increased though the image appears to be larger, therefore at 30 meters you will be seeing 30 meters worth of wobble though the target will only appear to be 10 meters away. What happens when the trigger is pressed is between the shooter's skill and inherent precision ability of the weapon.

I see what you mean...makes sense. I was actually referring to shooter error being magnified by the distance that the magnifier encourages rather than magnified by the optic, and in my mind I was thinking of a 1 MOA POA, but I can see that if the target is larger than 4 MOA then the accuracy shouldn't be affected given good shooting technique. Thanks for the clarification.

[zk556x45]

I prefer an H-1 with lower 1/3 co-wit via an LT660 mount. It's the perfect setup (for me) inside 300m.

zk

[Mo_Zam_Beek]

4 MOA dot and accuracy at a distance - power the dot down.


Good luck

[benw315]

Thanks everybody for the great info!! Now its just age-old dilemma of getting an aimpoint or eotech :fie: