I just recently purchased my first AR, a Bushy M4, so please forgive the newbie question...

I am looking at purchasing an Eotech in the next few weeks and I am confused about the whole cowtinessing issue...I plan on going with flip-up front and rear BUIS, with an ARMS #50C in the near future also.  I realize from the research that I have done that the only way to get the Eotech to cowitness on the ARMS is to mounted in the lowered region on the front of the rifle.  If for personal preference reasons I find that I want to move it to the flat top region of the ARMS what are the disadvantages?

I guess I am just confused about the andvantages of true cowitnessing.  If I plan on using optics excusively and only have BUIS for an optic failure type situation, what is the real importance or advantage of cowitnessing???  

Any comments or experieces would be greatly appreciated!!!

Good question and welcome to the site.

There are probably a lot more reasons a co-witness is good than I know.  But for me I've used the lower 1/3 co-witness with a Troy BUIS and an Aimpoint to check that my Aimpoint is still centered.  Basically if the Aimpoint takes a hard knock I can flip up the Troy, lower my head and when looking through the rear peep the dot will be sitting right on top of the front post.  This has come in handy a few times.

How do you mount something on the "lower region on the front of the rifle"?    If your talking about a lower 1/3 co-witness all that means is that you can "look over" the rear sight when its flipped up and still see the dot on the optic.  By lowering your face closer to the buttstock or buffer tube you can now look through the flipped up irons as well as see the reticle/dot on your optic.

What Jollyroger said... (I personally like the utility of being able to "check" my sights.)

I'd just add: try both an Eotech and an aimpoint before you buy, if at all possible. You might find that the Eotech reticle is a bit "busy" for true co-witnessing.  

I may be wrong about this, and I would appraciate knowing if I am, but I am under the impression that all of the ARMS SIRsystems require using the flat-top for mounting. meaning that if you mount your eotech on top of the flattop, it will be too high for co-witnessing. The "bi-level" SIR mounts might allow you to mount the Eotech on the handguards - I'm just not sure whether that makes for a true co-witness or just a bottom-third  co-witness.

Having toyed with different positions with mine - I'm thinking a handguard placement is going to be the solution for me.

Bob

Thanks for the responses!!!

Yes, you are right.  The ARMS SIR's use the flat top for mounting.  I am not sure whether the forward mounting allows for "true" cowitnessing or bottom third.  Their web site is not clear on that point.  

I have used an Aimpoint and was quite impressed with it, but I really like the reticle on the Eotech.  However, I have never used an optic mounted to the handguard region of the rifle, and was concerned as to how that would feel to me.  It seems like it would be a "reach".  

Maybe I am wrong in my thinking on this one.  That was my reason for asking what would be the disadvantage of mounting the Eotech on the flat top region of the SIR.  I know I would then be giving up the possibility of cowitnessing.  Are there other advantages to cowitnessing besides doing a quick check of optics zero position in the case of the optics taking a hit?

Thanks again for any info!!!

If you forget to turn the optic on it's faster to flip up the BUIS than turn on the sight.

I can't comment on this issue in reference to an EOtech (I have an Aimpoint), but I prefer co-witnessing using the center position where I can see the rear BUIS, red dot and front BUIS all in line. This provides me with an indication that my BUIS are still fairly well zeroed (if my red dot was). If I note a gross misalignment, then I am immediately alert to one or the other sight systems has a problem. If the red dot fails (battery), then I have a larger field of view in the bottom half of the scope without having to remove it unless there is any actual optic damage.

YMMV!

if you forget to turn your optics on...

Isn't the Trijicon reflex "always-on"?
Just another reason I'm urging him to try before he buys.
Don't get me wrong - he won't be wrong with an Eotech.

As to your question, the disadvantages...
This MAY be subjective, so take it with a grain of salt. It seems, and I have to add another qualifier here; I haven't got a railed forearm, so I can't physically mount it and see for real; but having said that; I tried just holding the Eotech above the barrel, and above the handguard, and it seems to me that I found my sight picture significantly quicker that way.
YMMV.
The short version of all that is that YOU might find that you like the "sight picture" far better with it mounted forward.
From what I've read and experienced, one of the main drawbacks of the Eotech is its reticle. I've described it as "busy".
Again, with all the qualifiers, I think mounting it further forward eliminates, or at least alleviates this "drawback".

Just something to think about...

I'm thinking of going with Eotech. A little cheaper than Aimpoint and I don't need to spend another $100 on a mount. I like the recticle and the 1 moa dot. I don't like the grainyness of the recticle tho. Odd thing is, the new ones I looked at seemed grainy but I looked at a used one yesterday that wasn't grainy at all. Problem was the guy wanted as much for it as I can get a new one with my LEO discount.

Quoted: I can't comment on this issue in reference to an EOtech (I have an Aimpoint), but I prefer co-witnessing using the center position where I can see the rear BUIS, red dot and front BUIS all in line. This provides me with an indication that my BUIS are still fairly well zeroed (if my red dot was). If I note a gross misalignment, then I am immediately alert to one or the other sight systems has a problem. If the red dot fails (battery), then I have a larger field of view in the bottom half of the scope without having to remove it unless there is any actual optic damage. YMMV!

I agree with you, that's the way mine's set up and I do like the fact that everything's lined up.  

There's another camp out there though that likes the lower third cowitness due to the fact that when sighting through the optic, they have an unobstructed view of the target below the dot reticule.  They can more clearly see what a suspect's doing with their hands, things like that.  With the absolute cowitness, the front sight post can obscure that portion of the target assuming you are holding up in mid-upper chest region.  Just a thought to ponder.

Quoted: Quoted: I can't comment on this issue in reference to an EOtech (I have an Aimpoint), but I prefer co-witnessing using the center position where I can see the rear BUIS, red dot and front BUIS all in line. This provides me with an indication that my BUIS are still fairly well zeroed (if my red dot was). If I note a gross misalignment, then I am immediately alert to one or the other sight systems has a problem. If the red dot fails (battery), then I have a larger field of view in the bottom half of the scope without having to remove it unless there is any actual optic damage. YMMV! I agree with you, that's the way mine's set up and I do like the fact that everything's lined up.   There's another camp out there though that likes the lower third cowitness due to the fact that when sighting through the optic, they have an unobstructed view of the target below the dot reticule.  They can more clearly see what a suspect's doing with their hands, things like that.  With the absolute cowitness, the front sight post can obscure that portion of the target assuming you are holding up in mid-upper chest region.  Just a thought to ponder.

Agree on the advantage of the lower third FOV, but my LEO days are long past and having to observe "catch and release" protocols are no longer an issue in any serious social discussion I may now have.

These days, if I'm looking at someone through my sights, the only thing in their hands better be their dick!

Thanks for all of the responses guys!!!

It looks like I have some more research to do, but you have all shared some good points.  

I think my rail system purchase may be determined by how I feel about the position of the Eotech once I have it.  I am curious to see how it feels to me located in the handguard region.

Many thanks!!!

Mini Range Report - Today I screwed down my Eotech and tried sighting it in.  I have some bugs to work out, but it's gonna be fine.  <for example, I learned that it makes a difference whether I look over my glasses or thru them... I've never noticed that with scopes. Also, that I need to work out whether I'm going to shoot with one eye open or two. I was taught to shoot with one eye closed; old habits are dying hard. >
I did notice that I liked the sight picture better with the stock fully extended. Makes me think I would like the optic over the handguards.
I liked it enough that I'd like to try it on a carbine with no iron sights at all - just the Eotech.

Thanks for the update.  I will be attending a gun show this weekend and will hopefully have the chance to simulate mounting the Eotech on the handguards.  Hopefully this will clear up my questions....