If your AR has folding BUIS - should your optics have absolute co-witness?

[DavidRSA]

Is the 1/3 co-witness better suited to non folding BUIS? If I have folding ones, wouldn't it be better to have my optics at a height where it the BUIS were flipped up, the co-witness would be dead center?

[pacrimguru]

doesn't matter, folding or non-folding, both types should be at the same height.

[LowSpeedHighDrag]

^ what he said. It's up to you if you want a lower 1/3 or absolute co witness.
Most people prefer lower 1/3. I use folding front and rear BUIS, but I keep the front one up at all times. If your red dot fails, you can can us your red dot window as a giant ghost ring for the front sight. It's extremely quick.

[DavidRSA]

doesn't matter, folding or non-folding, both types should be at the same height.

I understand that. I should have phrased the question as ... why have a 1/3 cowitness if you have folding BUIS... I want to order a new red dot, but think I should get the height of absolute cowitness since the BUIS wont get in the way...

Am looking at this mount:

http://primaryarms.com/product.sc?productId=18&categoryId=5

.. where it says... "IF YOU ARE GOING TO MOUNT THIS SIGHT ON AN AR15, USE THE DROP DOWN MENU TO UPGRADE TO THE HIGH MOUNT"
and I am wondering if its necessary since I have folding BUIS

[pacrimguru]

because whichever co-witness you choose, it is irrelevant what kind of sights you have.

most my rifles have flip ups and they are all 1/3 co-witnessed to their BUIS. i usually shoot with the sights down, but if i ever needed to line up a more accurate shot, i can flip up the BUIS and get my 1/3 co-witness on.

between 1/3 or absolute, that is personal preference.

[LowSpeedHighDrag]

I understand that. I should have phrased the question as ... why have a 1/3 cowitness if you have folding BUIS... I want to order a new red dot, but think I should get the height of absolute cowitness since the BUIS wont get in the way...

Am looking at this mount:

http://primaryarms.com/product.sc?productId=18&categoryId=5

.. where it says... "IF YOU ARE GOING TO MOUNT THIS SIGHT ON AN AR15, USE THE DROP DOWN MENU TO UPGRADE TO THE HIGH MOUNT"
and I am wondering if its necessary since I have folding BUIS

Whatever works for you, dude. I don't know what you'll be using your carbine for, but if it has anything to do with patrol carbine, military, or home defense rifle, I personally think the front sight should be kept up at all times.

[dieselpower]

I tend to say mount the optic as low as possible for your shouldered position. Some people set up a 1/3 with the mindset that they are going to need BUIS...seems to be an assumption to me. If Aimpoints are so great...why set your self up for the worst case that has little chance of happening?

Now if you are running some junk that has a strong chance to die, I think a 1/3 is a better way to play.

Its your firearm and you are the one running it.

I shoot Iron sights 75% of the time. I have fixed. I of course have 100% Co-witness since the time I do run my RDS I dont want to change cheekweld.

[Peter.Steele]

I understand that. I should have phrased the question as ... why have a 1/3 cowitness if you have folding BUIS... I want to order a new red dot, but think I should get the height of absolute cowitness since the BUIS wont get in the way...

Am looking at this mount:

http://primaryarms.com/product.sc?productId=18&categoryId=5

.. where it says... "IF YOU ARE GOING TO MOUNT THIS SIGHT ON AN AR15, USE THE DROP DOWN MENU TO UPGRADE TO THE HIGH MOUNT"
and I am wondering if its necessary since I have folding BUIS

Get the high mount, you'll need it no matter how you have it set up if you're putting it on an AR.


Quite frankly, lower third vs absolute is a little bit of a red herring and I don't understand the fuss. You're going to probably be zeroing both your irons and the red dot, right? So, presumably the dot itself is going to be sitting right on top of your front sight post, no matter what, right?

[dieselpower]

Get the high mount, you'll need it no matter how you have it set up if you're putting it on an AR.


Quite frankly, lower third vs absolute is a little bit of a red herring and I don't understand the fuss. You're going to probably be zeroing both your irons and the red dot, right? So, presumably the dot itself is going to be sitting right on top of your front sight post, no matter what, right?

I always thought that too. If you are going from RDS to BUIS...why do you care if its 100% or 1/3...the optic is dead. With 100% you have full FOV, with 1/3 you have more FOV over your target...it makes no sense to me to fuss over it when you are dealing with flip-ups.

Now fixed I see that some people like a less cluttered sight picture, so a 1/3 is better since you are looking over your BUIS most of the time...for an optics shooter that is.

[safaridave]

+1 for lower one-third.

[dieselpower]

I've got a question for those running lower 1/3 cowitness:

Prior to getting a red dot, I always used the small hole on my BUIS. Now, after mounting a PA micro red dot with lower 1/3, I can't see the red dot with the small hole and have to switch to the big hole. Is this normal/expected, or is my mount too high?

No, something is wrong. explain more please. you should be able to see your dot from any position. i can not see how the size of the peep blocks your view. I dont run a PA so maybe thats whats going on here. i didnt realize a PA RDS is not like other RDS.

how far back are you from the peep...where is your nose? is it touching the charging handle?

[Wherryj]

Here's a good article on co-witness.

http://www.weaponevolution.com/forum/showthread.php?2497-UNDERSTANDING-CO-WITNESS

[BAGunner]

I run my red dot at absolute co-witness on my folding sight upper. The lower 1/3 only make sense when the FSB cant be folded, where absolute co-witness will block half of the RDS's view. With folding sights, I can just fold them. In the case the RDS is out, I can fold iron sight back on, same cheek weld, same distance.
Besides, it's easier to zeroing in with absolute co-witness.

[ripcurlksm]

I understand that. I should have phrased the question as ... why have a 1/3 cowitness if you have folding BUIS... I want to order a new red dot, but think I should get the height of absolute cowitness since the BUIS wont get in the way...

Am looking at this mount:

http://primaryarms.com/product.sc?productId=18&categoryId=5

.. where it says... "IF YOU ARE GOING TO MOUNT THIS SIGHT ON AN AR15, USE THE DROP DOWN MENU TO UPGRADE TO THE HIGH MOUNT"
and I am wondering if its necessary since I have folding BUIS

Good luck with the M3, I just purchased the M4 yesterday, the only difference being the M4 has a 2MOA dot instead of 4MOA. Any reason you chose the M3?

[dieselpower]

I found a video online which illustrates my issue: HERE

Apparently, the diode at 6 o'clock blocks the front site post and is a couple mm too high. For reference, I have a 3rd gen PA micro.

wow didnt know that. Thanx man. Good knowledge there.