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Discussion Starter #1
Hi guys,

Does anyone know if the Zeiss Z-Point or Compact Point will provide a lower-third co-witness on the USC? I have the factory rail, but would be willing to change it out if necessary.

I found an old thread about this, and it says the Z-point does cowitness, but doesn't give specifics and the poster says that 'it is a pain' .. leading me to believe it sits very low and is more of an absolute cowitness, which is too cluttered of a sight picture for quick heads up shooting.
 

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I have the HDPS top rail on my USC and I measured the top of the front sight post to be approx 0.5 inch above the top of rail and the top of the circular front sight hood to be about 0.75" above
the top of the rail. After contacting many manufacturers, I could not find an RDS that mounts low enough to have the dot lie within the 0.5" to 0.75" space between the top of the front sight post to the top of the circular front sight hood. I then decided to find an RDS where the dot lies above the front sight hood, but not so high that you loose the check weld. I finally decided
on the Insight/Eotech MRDS EOTech Mini Red Dot Sight Advanced Kit w/ 1913 Mount and Shroud FREE S&H MRD-000-A11, MRD-000-A12, MRD-000-A13, MRD-000-A14. Insight Technology Red Dot Sights. One could purchase it as a kit which includes the picatinny rail mount
and metal protective shroud. When mounted, the top of the rail to the center dot measures 1.125". After trying it out, I think I made the right decision. Shouldering the USC, my field of view
is uncluttered with only a small amount of the top of the front sight hood showing at the bottom. Most importantly, I have a cheek weld. Other positives of this 3.5 moa sight are: battery loaded from the top, click elevation adjustments, light weight, some level of waterproofing, and lifetime warranty. Also the "looks" of the sight, I think, complement the lines of the USC quite nicely. FYI the Zeiss Z point measures 0.875" from top of rail to center of dot, so my belief is the dot would rest right above the top of the circular front sight hood. Thus the sight hood would be
to much a part of the field of view. The compact point I'm not familiar with. Hope this helps. Feel free to PM me if you'd like to know other measurements of other RDS's
 

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Discussion Starter #3
Thanks!

Any idea of how high the dot of a Burris FFII sits above the rail? Or an Aimpoint C3 in the factory low ring?

I have tried both of these optics on my USC, and find them to give me a very nice lower-thirdish co-witness. I don't like absolute cowitness, I prefer the dot to sit above the sights, and if I need the sights, I just lower my eye by a small amount.

The Burris isn't well made enough for me to be a primary optic, and the Aimpoint's permanent home is on a different gun. It sounds like the Z-point will give absolute cowitness.
 

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Amlew can you post a pic of your rig,im also interested in a RDS for my UMP conversion.
 

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The Burris Fast Fire II has an approx distance of 0.75'' from top of rail to center of the dot. The reason I say approximate is that, they were the one manufacturer out of several that did not have this data readily available. The customer service rep did the best she could to measure with a ruler. There was a post in the past on this forum from someone who said the fast fire will co-witness, but if it does, my guess is the dot is lying just under the top of the circular front sight hood, thus cluttering up the sight picture. I also agree with you in that I would rather spend more
to obtain a better quality RDS.

The Aimpoint ML3/Pro/M4 with factory low mount as well as the T1/H1 with factory mid height mount measures 1.18" from top of the rail to center dot. Thus it's sight picture would be very similiar to what I have. I chose not to go with Aimpoint mainly because of the weight. I would assume the dot quality is superior on the Aimpoints compared to what I have, but the farthest I will ever shoot is 100yds. Mostly I will shoot steel at 50 - 75 yds. I felt a good quality lightweight mini reflex RDS like the Eotech/Insight MRDS is a more appropriate choice for pistol caliber carbine.

I don't have the ability to post photos on this forum, but my rifle is actually quite conservative in mods. I have the RDS and a HDPS top rail. I also have the Hera USC stock which provides more
comfortable grip and more UMP like "look". Hera GmbH Splash Page I live in California and I am legally limited to a 10 round magazine capacity. Thus I decided it would not be worthwhile to invest in a full UMP conversion.
 

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Discussion Starter #6
You rule, man. Thank you.

If the Burris is about .75, and the Zeiss is .875, it should work fine for me after all. I'm not worried about the FS hood, because I already chopped off the top of it to clear up the sight picture, giving a more traditional HK sight picture - which I prefer.

Thanks again, I think I'm going to snatch up that Zeiss soon.
 

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I have the zeiss on my USC/UMP conversion and it works good but not great. The biggest problem is the poorly designed rear sight on the USC.
 

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Discussion Starter #8
Can you please elaborate? What about the zeiss and rear sight are problematic?

I'm guessing the aperture works fine, but the notch sits too low?

The cowitnesses irons for me are mostly for backup. I like the dot to sit on top of the sights and to keep a slightly elevated eye line for using the red dot. If the dot should fail, wash out, or if I need to grab the rifle without time to turn the sight on, or some such thing, I can just lower my eye line and get a tighter cheek weld to use the irons.

I run all my carbines in this fashion, and rather like it.
 

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I have a ump conversion with the HDPS rails, and they do sit slightly high.
I currently have an insight MRDS with an aftermarket quick detach ADM mount. it does NOT cowitness at all, which is why I went with the quick detach adm mount so that if I have to use irons, I can flip the lever and take the insight MRDS off. The insight works fine but I have the fatter dot and it really covers up a lot of view when trying to hit a 6in circle at 100 yards.

The other alternative I was playing around with was the aimpoint micro. I have a spare R-1 so I was considering on changing it out to that. With the factory mount it WILL cowitness rather nicely.
I'm all about cowitnessing, but hk UMP/USCs piss me off with their factory front sight. The front post hood covers a GREAT deal of sight picture when using a red dot which has frankly deterred me from cowitnessing. I've seen some people get around this by opening up the hood but I try to leave the firearm as factory close as possible.
 

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FYI, the ADM mount is dimensionally identical to the the Insight factory mount. Top of rail to center of dot 1.125".
 

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I have a ump conversion with the HDPS rails, and they do sit slightly high.
I currently have an insight MRDS with an aftermarket quick detach ADM mount. it does NOT cowitness at all, which is why I went with the quick detach adm mount so that if I have to use irons, I can flip the lever and take the insight MRDS off. The insight works fine but I have the fatter dot and it really covers up a lot of view when trying to hit a 6in circle at 100 yards.

The other alternative I was playing around with was the aimpoint micro. I have a spare R-1 so I was considering on changing it out to that. With the factory mount it WILL cowitness rather nicely.
I'm all about cowitnessing, but hk UMP/USCs piss me off with their factory front sight. The front post hood covers a GREAT deal of sight picture when using a red dot which has frankly deterred me from cowitnessing. I've seen some people get around this by opening up the hood but I try to leave the firearm as factory close as possible.

This is correct. I have the FF2 and you have to get your face all the way down on the cheek wield in order to co-witness.

I like the size of the FF2, but that's about it. I think I'd rather have an RMR04 on a high mount and remove the front sight or get a Eotech EXPS2.0

The RMR04 takes no battery so this might be best.
 

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Discussion Starter #12
So, I take it the HK factory rail sits lower than the HDPS rail? Is that right?

I opened up my front sight, and have the FFII mounted on an HK rail. I like this set up a lot. The front sight does take up some of the sight picture, but that isn't an issue for me. Both eyes open, the front sight kind of disappears anyhow and I can just put the dot where I want it. If the dot goes out, or if I need to snap a shot quickly when it isn't on, I can just drop right down to the irons.

I use this sort of set up on all my guns, and I find it works great for me.

My only concern with the FFII is that it is no where near the quality that I normally go for. I bought it, originally, to test whether I like the micro sight concept. I do, so I bought an RMR. It is a nice little sight.

I also have a Meprolight M21 tritium sight, and I have used other Trijicon's tritium products. The M21 has the brightest reticle of them all - but even it is very prone to wash out. For range work, hunting, or so on it is wonderful. If you're using it with an eye for any sort of home defense or combat application, they are really no good. If someone points a flashlight at you, you lose your reticle. If you have a bright flashlight on the gun and turn it on, you're going to lose your reticle.

Tritium systems are great - but you absolutely need to have cowitness ability if you're going to stake your life on it.

Even then, it doesn't make a lot of sense to me for most applications, to tell you the truth. An Aimpoint on setting 7/10 can run on a battery for 5 years 24/7. After 5 years, your tritium is going to dim fairly significantly. Two batteries will last you longer than the usable life of tritium, and you can actually adjust the reticle brightness as you see fit.

I use my RMR on a handgun. I like it because it has a nice slim profile, draws nicely, is always on, and I have it co-witnessed with my irons. If Aimpoint made a similar profile reflex sight with their life-battery life ACET technology, I'd switch.
 

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How does the sight picture/co-witness of the fastfire compare to the RMR? From my info, the RMR should mount almost as low as the Fastfire. I wanted to get an RMR as well, but I did not want to open the front sight hood, and was concerned with the hood cluttering the sight picture, Trijicon does make another mount that is taller for the RMR, but that one was too tall and I was concerned with loosing the ability for cheek weld. The Insight MRDS mount height was in between the two Trijicon RMR's, so I went with that.
 

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Discussion Starter #14
Not sure how the RMR would mount on the USC. From the looks of it, it should be about like the FFII, as you note. The FFII gives a nice lower co-witness.

I can't test my RMR on the USC, because I don't have a picatinny mount for the RMR. It is bolted right to my slide.

But you should really contemplate opening up that FS. It really isn't hard, and if on the off chance you do mess it up somehow, you can get a new factory FS assembly from hkparts for $16.

I just eyeballed where I wanted the hood cut, and marked it with a pencil, then went nice and slow with a hacksaw and cleaned up the edges with a file and some sandpaper.
 

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Thanks for the encouragement about opening up the front sight, but now that I have the Insight MRDS, I cannot co-witness at all. When I look the rear aperture, I see the base of the sight and top of the mount. Also, I always felt that when using the iron sights, my head was tucked down too low. It was somewhat uncomfortable for me. With the Insight mounted, my head is little more upright and I still have a cheek weld.
 
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