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Discussion Starter #1
I just ordered a Burris 135 red dot from Natchez, on sale for $99. My question is, what mount would you suggest to co-witness with my fixed front post? I've looked at the 1" burris high rise and the vortex cantilever. Any others I should consider? Not sure if I'll ever add a magnifier or not but I'm leaning towards the vortex to keep the option open. What say you?
 

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A couple of quick thoughts. If you are pinching pennies, take a look at Primary Arms options at the online site--good quality and very competitive prices for that quality. Go cantilever if you think you might want to add a magnifier. Otherwise a basic mount should serve your purposes. You should consider a 1/3 co-witness; that will allow you to use iron, but won't distract you from the red dot.
 

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Discussion Starter #3 (Edited)
Thanks slim, having never had a red dot before, I could use all the advice I can get. I will give primary arms a look. Does using a cantilever mount without a magnifier place the sight too far away in your opinion?
 

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I have some problems with popular terminology. I would take this to Arfcom but I think we can discuss things in a more civilized manner here. In the first place, I understand why 'lower one-third' came about although I find it pointless. Absolute co-witness means when using the red-dot and iron sights AT THE SAME TIME, which is ridiculous, the red-dot will sit on top of the front sight post. I accomplished this with an EOTech with built-in base. I separately sighted in the EOTech and BUIS at 50 yds with the same ammo, so with the sight 'on' and the BUIS up, and sighting with the sights, the red-dot sits right on top of the front sight post. As neat as this is, I know of no practical application for it. 'Lower one-third' proponents say with the front sight lower in the field of view, it does not occlude any of the target when using the red-dot. But in fact, one of the primary benefits of the red-dot is that it doesn't matter where in the field of view the red-dot appears when sighting the target - it always shows the POI (within the limits of sight-in range, trajectory, vertical angle, parallax, etc.). So, even with absolute co-witness, with the BUIS folded down, you can move the red-dot around in the field of view - over the top of the front sight or to either side of it - and the bullet still follows the dot. The other aspect of the red-dot that is so great is, unlike iron sights, there is nothing to 'line up' - all you do is put the dot on the target and fire - much faster than iron sights. Of course, at longer ranges you want to put the dot closer to the center to minimize the effects of parallax but out to 100m it really doesn't come into play. And you can always turn the dot off and use the BUIS right through the optic's lens. The EOTech with it's large 'screen' makes dot manipulation much easier because there's so much more room to use. That's why I like my red-dots close to the eye - expanded field of view.

So, since there is no need to use the dot and the sights at the same time, since it defeats the purpose of the red-dot sight, why should you go to the trouble to mount your optic higher on the rifle, forcing you to expose more of your head when sighting, just to gain more space for the red-dot that you really don't need?
 

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Discussion Starter #5
Lots to process saxman. To answer, I'm not sure. Thanks for the info. As my name implies, I'm a bit simple when it comes to ars especially. Trying to learn and I appreciate the advice. Keep it coming.
 

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I have some problems with popular terminology. I would take this to Arfcom but I think we can discuss things in a more civilized manner here. In the first place, I understand why 'lower one-third' came about although I find it pointless....
I agree!
 

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Properly used, there is no field of view for a true red dot sight.
You mount the gun, the red dot appears....Shoot with both eyes open and the bullet goes more or less where the red dot appears to be on the target.
Stop squinting through your red dot sight. If you have a scope with an illuminated dot or post, you have a scope. Look through it.
 

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Thanks slim, having never had a red dot before, I could use all the advice I can get. I will give primary arms a look. Does using a cantilever mount without a magnifier place the sight too far away in your opinion?
It shouldn't put the red dot too far away; you have enough flexibility on rail placement to adjust it like you want. I like the eyepiece on my Aimpoint about 3" or so forward of the charging handle (shooting nose to charging handle). A cantilever should allow that and still allow you to pop up the RS when you want/need to use it.

Good luck.
 

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Since you already placed the order for the Burris 135, and your front sight is Fixed. I'd opt for a cantilever mount that places your dot in the lower 1/3 co-witness range. If you have folding sights, I'd opt for an absolute co-witness. You should also take into account if you plan to change the configuration of the gun up later.

Absolute co-witness generally provides for a better cheek weld.
 

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You don't need a cheek weld with a red-dot either. I put one on my AMD65 on which a cheek weld is impossible. With a red-dot, it doesn't matter. Whatever the dot covers will be hit (assuming sight-in, yada, yada) regardless of where the dot appears in the optic's lens. That's what makes it fast! And, I do use such optics and sights with both eyes open, but I still like the 'screen' close. I know that's not popular, but who cares? And again, there is no 'co-witness' unless you have the sight up at the same time the red-dot is on, which is beyond ignorant.
 

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My Aimpoint Comp M4 came with a mount the perfectly co-witnessed with the flip up sights on my KAC SR-15. Since I used these sights to zero the rifle, it was a simple matter to zero the Aimpoint. In fact, I did it in the gun shop prior to leaving for the range. In the unlikely event I forget to change the AA battery in the M4 and 5 years have passed and the battery has died, I just flip up the sights and I'm still on target.

I can score hits on a 10" plate at 300 yards without having to resort to hold over and can shoot easy 100 yard groups at <1 MOA from the bench, using 75g Hornaday Match ammo.

Of course, this comes at a price. An SR-15 runs right around 1700 and the Comp M4 was $600 used. Can't beat the quality though.
 

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There are two 'fields of view' to consider with an unmagnified red-dot sight; the total FOV and the FOV of the reticle, which is limited by the physical size of the lens. IOW, the reticle can only appear within the boundaries of the lens. The larger that lens is, either by physical size or by proximity to the eye, the greater the field of view of the lens area, or possible reticle positions relative to targets. Depending on an individual's eyesight limitations, sight position may have to be based on being able to focus on the reticle.
 

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There are two benefits to co-witnessing an RDS with BUIS:

1) You use the same cheekweld regardless of sighting system (as opposed to lower 1/3rd).

2) In the OP's case, since he's using a fixed front sight post (and presumably flip up rear sights) he can use the downed RDS as a large ghost ring style rear aperture sight for up distances up to 25 yards without having to flip up the rear sight. Having the front sight already co-witnessed facilitates this (as opposed to lower 1/3rd).

With that said, other posters are on point that you would not bother to line up the active RDS dot with the BUIS.

One final note: if you do any serious course work or range work with your $99 RDS, it won't take long to fail or lose zero. If on a budget, you'd be better off finding a used Aimpoint.
 

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You don't need a cheek weld with a red-dot because there's nothing to line up. Co-witness has no practical application - it's a curiosity.
I noticed that about a red-dot too, that at close range the dot doesn't have to be turned on to get combat hits as long as you keep the front sight in the same place for a reference. And that works whether or not you have a rear sight or any co-witness.
I don't do 'course work' and once sighted in, there's no 'range work' either except annual qualifying. I'll be sure and post if anything ever goes wrong with my inexpensive red-dot but I'm not expecting any trouble with it.
 

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You don't need a cheek weld with a red-dot because there's nothing to line up. Co-witness has no practical application - it's a curiosity.
I noticed that about a red-dot too, that at close range the dot doesn't have to be turned on to get combat hits as long as you keep the front sight in the same place for a reference. And that works whether or not you have a rear sight or any co-witness.
I don't do 'course work' and once sighted in, there's no 'range work' either except annual qualifying. I'll be sure and post if anything ever goes wrong with my inexpensive red-dot but I'm not expecting any trouble with it.
The cheek weld is one of the 4 points of contact (5 if prone using a 30 round mag). When using an RDS this cheek weld will be different if the RDS is not mounted at co witness height. For example, if it's mounted higher to create a lower 1\3 rd then the operator has a different (higher) cheek weld when using the RDS versus when using the BUIS.

Again, co witness is NOT about aiming by lining up the RDS with the BUIS. It's about maintaining the same points of contact and having a ghost ring sight you can use in a pinch at shorter ranges.
 

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Discussion Starter #16
First, thanks for all the replies. I've learned quite a bit.

Secondly, I believe this little Burris is going to reside on my 10/22 for a bit until I decide if I can effectively use one. I've had a bit of damage to my right eye and developed a bit of astigmatism in it. Left eye, clear dot, right, small cluster of grapes. Combined I think I can deal with it.

As for a $99 red dot, I had a grand in the budget. An $885 Colt 6920 and a $100 Burris seemed better than a $600 DPMS and an Aim point in my opinion. Especially since I wasn't sure if my eyes would like a red dot sight. .

Think I'll concentrate on using the irons for a few hundred rounds.

Thanks again everyone, you've been very helpful.
 
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