Standard height for co-witness?

I ran across something interesting last week when I decided I wanted a QD mount for my Romeo 4T https://www.sigsauer.com/store/romeo4t-1x20-mm.html. I called up Sig to confirm what mounts are compatible, and they told me any Aimpoint would be fine, so I ordered an ADM https://www.americandefensemanufactu...w/product/208/and figured it would be a no brainer. Well, once the mount showed up I immediately noticed it's a bit taller then the one that came with my red dot, so after doing some research I now see that the Sig mount is 1.41" and the ADM is 1.52".

How can that be? I had assumed that all co-witness are the same, but now I'm starting to think that maybe Sig lied to me and a standard Aimpoint mount won't work with their optic. God knows the seem to be in love with their proprietary systems lately, is this what I'm experiencing? Can anybody else shed some light on why there might be two different co-witness heights for these mounts?

I checked Pappabear's Romeo against irons. It won't cowitness right. My holosun does the same crap. Lower 1/10th or something that makes irons useless.

Not every manufacturer uses the same height for co-witness and lower 1/3. For example:

Irons are supposedly 1.41" over the top rail.

Aimpoint's stock mount has a 39mm spacer which is 1.535".

Geissele is 1.41" for co-witness and 1.57" for lower 1/3 (based on an email response I received from them).

ADM is 1.52" for co-witness and 1.69" for lower 1/3.

Larue is 1.4" for co-witness and 1.64" for lower 1/3.

Bobro doesn't list measurement that I could easily find, but they have a co-witness, lower 1/3, and tall mount, and most people say their tall model is similar to the Larue/ADM lower 1/3.

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Originally Posted by Slippers

Not every manufacturer uses the same height for co-witness and lower 1/3. For example:

Irons are supposedly 1.41" over the top rail.

Aimpoint's stock mount has a 39mm spacer which is 1.535".

Geissele is 1.41" for co-witness and 1.57" for lower 1/3 (based on an email response I received from them).

ADM is 1.52" for co-witness and 1.69" for lower 1/3.

Larue is 1.4" for co-witness and 1.64" for lower 1/3.

Bobro doesn't list measurement that I could easily find, but they have a co-witness, lower 1/3, and tall mount, and most people say their tall model is similar to the Larue/ADM lower 1/3.

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I figured it was something like that, but good to get confirmation from and industry guy. It's pretty surprising that it hasn't been standardized. Any idea why?

On a different note, and a tad off topic, I love my new Arisaka inline ring mount. Tucks in real nice on my MCMR, thanks again for your help tracking one down.

Does anyone know the actual height of the Romeo 4 reticle from the bottom of the mountless housing? I know the side battery tray Holosuns are close to 2mm taller than my Aimpoint T1s but the screw on battery cover models are less than 1mm different(if that much).

The mount Holosun sends out with their battery tray versions is supposed to be shorter to compensate for the greater height from optic body mounting surface to optic center at the reticle. That might be the case with the OPs Romeo 4 mount as well.

I really like some of these new circle dot reticles and I like Solar but up until now none of the solar models was the correct height to line up with everything(magnifier, PVS14, Anglesight) when using a high end T1 mount like a Bobro, KAC. ADM, etc.

Quote:

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Originally Posted by Mr McSimon

It's pretty surprising that it hasn't been standardized. Any idea why?

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[Necroposting galore] One possible reason is that they are going off different sights. The optical axis sans mount of the Aimpoint T-2/H-2 is slightly higher than the older T-1/H-1 (less than 2 mm or 0.079" IIRC,) which means that even if several mounts are the same physical height from the Picatinny to the footprint holding the sight, if you mount a T-1 it will be one height and a T-2 it will be another. [/Necroposting galore]