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How Does the MR920 Optic Cut Work?

Coming to you from SHOT Show 2020, where we are talking about how our new patent pending optic cut on the MR920 works. A few of you asked questions about how the optic stays in a rigid mounted position, so we’re going to explain that now.

When you take a look at what the optic cut looks like with the optic removed. You can see that we have relocated the extractor depressor plunger assembly, which allows us to drive the screws deep, deep into the slide, in fact they come out almost at the rail. Ok, so we’ve got long screws, but you’ll notice that there are no bosses or posts, so how does the optic keep from twisting? We did something a bit unconventional here. The mounting system comes with screws that are designed for each specific family of optic, for example the ones shown here are for the RMR and Holosun optics. You’ll see on the section of the screw that does not have threads that it is about the same diameter as the hole int he optic, which reduces a lot of the fit between the optic and the gun at that location. But the secret sauce is actually in the spacer. On the back of the optic cut, there are two small half circle openings in the slide that are designed to receive a corresponding half circle on the spacer. The spacer is designed with the outside diameter of the optic in mind. If you were to just mount the optic to the gun, you would have a little space at the back–we didn’t like that just from an aesthetic perspective. But more importantly even if the screws are tightly torqued and properly loctited, with a strong enough blow the optic could potentially turn or twist a little bit–and I know that because we pounded on them with a deadblow hammer as part of our testing. So what we did was to design a spacer out of extremely hard plastic. The spacer is keyed to lock into those little cavities and it is designed to be just a little bit oversized so that it has to compress under pressure as you install the optic. When you put your screw into the optic, it compresses the spacer at the back and puts it under a substantial amount of pressure. The screws are machined out of a material that is very strong in its own right and something else to note about these screws is the broach cut opening, which makes it extremely difficult to strip these screws. As soon as those screws are torqued to 10 inch pounds, the optic is drawn tight toward the back, compresses the plastic of the spacer, and creates an incredibly rigid mounting system because the optic cannot turn once it’s under compression. Each optic has different spacers to fit this slide.

19 Replies to “How Does the MR920 Optic Cut Work?”

  1. Sully says:

    Can you have the optic cut configured irons forward??


      We debated on this configuration, but many customers choose not to mount and optic immediately and some never do. We wanted them to have the longest sight radius possible so we chose the conventional configuration. We do not have plans to produce the gun irons forward and could not support this as a custom order.

  2. Wes says:

    I have a MR920 on order. Is there an expected ship date?
    Thanks, I can’t wait to get the 920 in hands!


      You should see your gun in late March or Early April

  3. Isaiah says:

    I own a mr918 and was wondering if i send in the slide will y’all do the same sight cuts on it as the mr920 has ?


      Hi Isaiah, I am sorry but the optic cuts cannot be added post-production.

  4. Kevin says:

    I bought a used mr920 elite and the mounting screws didn’t come with it. Will the mounting screws that come with the optic work or do I need to order a set from you when they come back in stock? I can’t mind the screw specs to compare and I don’t want to strip out the holes.

    1. Jessica Roe says:

      Email me your address and the optic you are mounting and I will get some sent out to you– jessica@shadowsystemscorp.com

  5. Brian says:

    Do you know if the swamp fox sentinel works well and needs the spacer or not. I have one and hoping it will work when I get the gun. I am also hoping the iron sites still work.

    1. Jessica Roe says:

      Hi Brian, We have not tested the Sentinel. There are other Swampfox models on the approved list. If you head over to MR920: How to Mount your Optic (Optic Ready Slides ONLY) you’ll see an updated version of the tested optics list.

      It sounds like you already have the Sentinel–if you do end up mounting it, let us know if it does fit and we can add it to the list of optics we will test in house!

  6. Wilson says:

    Hi MR920 Elite is it can be use sig Romeo 3max with out mounting plate?

    1. Jessica Roe says:

      The only Sig optic that has been tested and approved is the Romeo Pro 1.

  7. kando says:

    Question regarding the difference between the iron vs optics: Is it true that on the optics version y’all use a short extractor assembly, rather than a long extractor on the iron version? This is regarding the combat models

    1. Jessica Roe says:

      Yes, that is correct.

  8. Bryan R Reiser says:

    I have a swampfox liberty and the screw heads are just a tad too big, and hang over the battery cover. What would be recommended to remedy that? File them down ever so slightly or get different screws?

    1. Jessica Roe says:

      Unfortunately, that is just the way our screws interface with the Swampfox. Some customers have experimented with turning the screw heads down a bit and had success with it, but it is not something we have tried. Also, please be sure you’re using the #1 screws with the Swampfox Liberty.

  9. Francis Enriquez says:

    I tried to mount a Hex Dragonfly on my MR920 and the screw holes on the slide were too far back. Any suggestions to get this red dot to mount?

    1. Jessica Roe says:

      That optic is not one we have tested. You can find a list of optics we have tested and approved for the optic cut here: MR920: How to Mount your Optic (Optic Ready Slides ONLY)

  10. Brady says:

    If you think of your optic cut as a giant picatinny rail section shouldn’t you be wedging the optic tightly to the front? This way when the weapon recoils and the slide reciprocates to the back the front of the optic is already tight against the front of the cutout or spacer and has nowhere to go. With the two spacers that go behind the optic you theoretically can have the optic move forward. I am asking because the Holosun 508T I have doesn’t fit snugly in the cut out with spacer A in place.

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