Co-witness question
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Old 12-20-2011, 01:44 AM   #1
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Default Co-witness question

My Carbine should be here any day and I needed a rear sight , so I bought a Magpul MBUS rear , My question is will I be able to Co-witness thru a Primary Arms microdot with this setup or is it to small ? It says lower 1/3 on the ad but I want to know from someone using that setup that it works.
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Old 12-20-2011, 02:10 AM   #2
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well if your referring to co-witness when looking through the sights and the sights and dot are on the poa at the same time while looking through both, then No. your dot will be above the target when using irons and your irons under the target when using the dot.

i prefer absolute co-witness when both are poa at the same time. magpul mbus height is 1.5" above rail. heights are typically measured to the center of the optic. so you would need a mount that puts the center level with the sights

got a link to the sight your looking at??

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Old 12-20-2011, 02:15 AM   #3
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https://www.primaryarms.com/Primary_Arms_Micro_Dot_With_Kill_Flash_PA_Ris_p/md08pariserbundle.htm


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well if your referring to co-witness when looking through the sights and the sights and dot are on the poa at the same time while looking through both, then No. your dot will be above the target when using irons and your irons under the target when using the dot.

i prefer absolute co-witness when both are poa at the same time. magpul mbus height is 1.5" above rail. heights are typically measured to the center of the optic. so you would need a mount that puts the center level with the sights

got a link to the sight your looking at??
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Old 12-20-2011, 02:20 AM   #4
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I guess my question is is it going to fall in the lower 1/3 with irons on the front and theh MBUS on the back ? absolute would be great but if it works Im not going to be that picky for the price .

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Old 12-20-2011, 02:34 AM   #5
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from looking at their page it doesnt come with a mount. the drop down has a absolute co-witness addon for 40$ i could be reading it wrong. you might want to call them and ask

ive got the vortex sparc and strikefire. the sparc comes with mounts for 1/3 and absolute. the strikefire comes with an absolute or no mount.

military arms channel on youtube has a sparc review and order code for 20$ off from 3 rivers precision. one of the vendors for the forum here might be able to beat both prices

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Old 12-20-2011, 02:57 AM   #6
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The pa model comes with alow mount, unsuitable for use on a conventional ar flatop.

You much opt for an additional mount. Thbe qd mount by pa is for a lower 1/3 co witness.

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Old 12-20-2011, 01:13 PM   #7
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The pa model comes with alow mount, unsuitable for use on a conventional ar flatop.

You much opt for an additional mount. Thbe qd mount by pa is for a lower 1/3 co witness.
I did get the PA QD mount for it , I just wonder if the extra $40 is worth it for the absolute ? What ya think I can call and get my order changed before it ships this morning
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Old 12-20-2011, 02:05 PM   #8
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I'm pretty sure you can.

I prefer lower 1/3 over Absolute.

Hey that sounds like a drink.......

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Old 12-20-2011, 02:10 PM   #9
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The difference is pretty small, my belief is that the best system would be more closely suited to you physical attributes.

How tall and what size hat do you wear. Is you head the size of a grapfruit or watermelon ? O.o

Lol I kid.

An absolute is more suited to smaller heads. Lower 1/3 for bigger heads imo. A consistent check weld must be practiced and developed first for you to even form an opinion. Don't stress too much about it.

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Old 12-20-2011, 02:38 PM   #10
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I haven't worked with those RDS/mounts you ordered but with my TRS-25 and a tall mount I get a bottom 1/3 cowitness with my MBUS, which I like for zeroing as the dot is lollipoped on the A2 front sight when I look through the aperture. If I look over the rear sight the dot is floating above the front sight, maybe at a top 1/3. If I flip down the MBUS the dot is in the center of the glass. Is this how you want to set up your RDS purehavoc?

Of course as AgentTikki pointed out I do have to change my cheek weld to move the dot around. Normally of course the MBUS is down because the dot is much dimmer when you look through the aperture.

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