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MR920: How to Mount your Optic (Optic Ready Slides ONLY)

This post is about how to install an optic onto the new patent pending optic cut featured on the MR920. For instructions for MR918 models, see this one.


MR920 Optic Mounting (Optic Ready Slides ONLY)

Overview: The patent pending Shadow Systems optic mounting system provides a low profile, high strength, multi-brand optic mount for your pistol.  The system is unique in that it accomplishes this without the need for adapter plates or shortened screws.

The threaded holes in the slide fit corresponding holes on many optics in the market.  If your optic fits in the recess in the slide and lines up with a set of holes, you can likely mount it on the pistol. 



Preferred Mounting  with Spacer (RMR, Holosun, Vortex Viper, Leupold DeltaPoint Pro):

For maximum strength, the system incorporates a high strength polymer compression spacer either in front of or behind the chosen optic.  This spacer is not required to keep the optic affixed to the slide.  However, it does add rigidity to the system and offers a buffering effect in extreme use/hard use environments.  The spacers are sized specifically for certain, commonly selected optics.  However, they may accommodate other brands which have a similar outer footprint.

The included spacers are designed specifically to fit the Trijicon RMR, Holosun with RMR-style footprint, Leupold DeltaPoint Pro, and Vortex Viper.  Depending on the outer footprint of your chosen optic, the spacers may accommodate other optics as well.  Check fit to determine if they will work for your optic if it is different from those listed above.  You may also, in cases where a spacer is too large for the optic you have chosen, carefully modify the spacer with sandpaper to fit your optic.

The spacer is designed to be slightly oversized for the space that it occupies when the screws are tightened.  By being slightly oversized, it remains under compression after the optic is mounted which removes all play in the system and creates a rock-solid mounting solution for your optic.


1. Refer to the table above to select the correct spacer and screws for your optic.

2. Install Spacer at the front or rear of the optic recess in the slide per the table.

3. Place the optic tight against your spacer and ensure screws are aligned over the holes in the slide.  Note: You may notice the screws are slightly misaligned from front to rear.  This creates the compression against the spacer when the screws are tightened.

4. Push the optic flat to the floor of the recess in the slide.  Some optics will fit very tightly.  You should be able to press the optic flat to the floor of the recess.  If you cannot press the optic to the floor of the recess with firm finger pressure, call customer service at 469-458-6808 as your optic may be oversized and an extra step may be necessary.

5. Shake the included bottle of Loctite 243 for 20-30 seconds.  Break off the tip and prepare your screws by applying a small bead to the threaded section of the screw only.  DO NOT put Loctite in the holes in the slide as it can bind certain internal assemblies.

6.Carefully place your screws into the holes in the optic and thread them downward stopping before the screw reaches the optic.  Before the smooth portion of the screw reaches the optic, place a large drop on the smooth portion of the screw.

7. Finish threading the screw into place and tighten to 10-20 inch pounds with a T-10 Torx tool.  If you do not have a torque wrench and are using a typical hand tool, most people describe this as “very snug, but not excessively tight.”

8. If you applied the correct amount of Loctite to the smooth portion of the screw in step 6 above, you will have some “squeeze out” around the head of the screw once tightened.  Carefully wipe this away with a Q-tip or rag.  Be careful not to wipe Loctite onto the laser emitter that is normally at the rear of the optic body.

9. Allow the Loctite to cure for 24 hours before shooting.  It is easily removable with hand pressure if needed for battery replacement, etc.  You can store extra Loctite 243 by inserting a pin or nail in the end of the tube.  It has a shelf life of about a year in most cases.

Mounting Without Spacer (Other brands):

If you do not have one of the optics listed above, but your optic fits in the recess in the slide and lines up with a set of holes, it can be mounted to the slide.

1. Experiment with the included screws to find a set that fits through your optic and can be fully tightened against the body of the optic (does not bottom out).

2. Follow steps 5-9 in the section above.  Since you will not have the benefit of a spacer to help with alignment, as you tighten the screws, visually align the optic using the front or back of the optic recess as a visual reference.  It does not need to be perfect, it is just a good idea to make sure it is not twisted to one side as sighting in will be easier.

Note on optics with windage and elevation locking screws on the rear:  Some optics (Vortex Viper, TruGlo Tru-Tec, etc.) feature locking screws for windage and elevation adjustments that are located on the back of the optic.  Since our system recesses the optic to achieve a low mounting position, these screws will not be accessible once the optic is mounted due to the position of the rear sight.  To access the locking screws, you must drift the rear sight out of place.  We are sorry for the inconvenience, but the only way around this would have been to eliminate the rear sight or mount the optic in an undesirable high position.  We recommend drifting out the rear sight, following the mounting and zeroing procedures for your optic, tightening the windage and elevation locking screws (which are accessible with the rear sight removed), then reinstalling the rear sight.

Note on Co-Witness with Leupold DeltaPoint Pro: The Leupold DeltaPoint Pro has an extremely high body that prevents a co-witness even though we have deeply recessed the optic in the slide.  We are sorry for the inconvenience, but the only way around this would have been to use extremely high sights which would have created an unacceptable co-witness with all of the other brands we fit.  If you would like sights that co-witness with the DeltaPoint Pro, you may select aftermarket sights that are designed for a Glock-style dovetail.  Be aware that you will want to choose a rear sight that is relatively thin from front to rear to prevent interference.  For reference, the MR920 sight is 0.279” from front to rear.

29 Replies to “MR920: How to Mount your Optic (Optic Ready Slides ONLY)”

  1. JT says:

    I have the MR920 with the optic cut and am attempting to mount a Trijicon RMR. Is there a tool included with my MR920 to remove the screws for the optics plate that came mounted from the factory? …or do I need to purchase a tool, on my own, to remove these OEM screws?


      It is a common T10 Torx bit that is needed to remove those screws. They can be found in stores such as Walmart, harbor freight, northern tool and the like.

  2. Latif Jenkins says:

    Luis and Richie are the best!!! I have a 920 an my guns shoots amazing!!!!

  3. Jerry Jennings says:

    Just purchased your MR920L and I couldnt be happier. The pustol is amazing and it has now become my “Go To” carry piece.

    Question: Will the upgraded holosun 508T v2 from the Holisun 507C fit my slide?

    1. Jessica Roe says:

      Hi Jerry, yes, it will fit.

      1. Tom Harper says:

        Jessica, on the Holosun 508T V2, is it recommended to use the #1 screws as with the 507C V2?

      2. Jessica Roe says:

        Yes, that is correct.

  4. Rick Wright says:

    Does anyone know the thread type for the 7/16″optic mounting screws?

    1. Jessica Roe says:


  5. Alan Puckett says:

    I have a MR920 Elite, I am replacing my RMR with a Holosun 507C. One of the screws is stripped and I need to replace it. It appears the same screw type is used for RMR & 507c,4-40 5/16?
    You are out of stock, is screw specific for the Shadow Sytems? I cannot locate one anywhere.

    1. Jessica Roe says:

      Please email me your address to jessica@shadowsystemscorp.com and I will get a new screw sent out to you.

  6. David Barta says:

    The new style Holosun 507c does not work with the #2 screws as specified. The #1 worked better. The #2 heads were too large to be screwed all the way into the counterbore of the optic. If compared to the supplied screws with the Holosun, the #1 screw head size is slightly smaller, but acceptable in size. The #2 however is larger and therefore will not work.

    1. Jessica Roe says:

      David, we did a Technical Tuesday video about this recently. Holosun changed the screw holes on the newest generation, so we now recommend using the screws the manual recommends for use with the Viper.

  7. Tony says:

    Just picked up my MR920, I’m stoked! I was considering fitting it with the new Holosun 509, however I was told the mounting is different. Can you confirm whether or not the 509 is compatible with the MR920? Thank you

    1. Jessica Roe says:

      The 509T can SOMETIMES be used with optic cover plate screws. It can be tightened, but the head will sit high. Some 509Ts will fit, some will not. We are working on different screws.

      1. Dustin says:

        Pardon me ma’am…How can only “some” fit? That comment makes absolutely zero sense. It either fits or does not with the Mr920 and 509T. Being as this statement is coming from the manufacturer “maybe” or “sometimes” is quite confusing to the consumer. Please clarify, Thank you.

      2. Jessica Roe says:


        I understand your frustration–this is why we have NOT added the 509T to our approved optics list for our pistols. Of the 509T samples we have tested, SOME of them mounted with our optic cover plate screws and some samples did not–likely due to allowed variance at Holosun in the manufacturing of the optics. We are working on new screws for this optic, but until then, we cannot recommend this optic as not all of them will fit with the screws provided.

  8. Daniel Rivera says:

    Will this mount work with both SIG Romeo 1 Pro versions? SOR1P100 and SOR1P103?

    1. Jessica Roe says:

      Hi Daniel, The version that we have tested is SOR1P101. We have not tested the other versions.

  9. Jose Boix says:

    Is there a solution which will allow mounting of the Vortex Venom to the MR920 Elite?

    1. Jessica Roe says:

      No, unfortunately the optic body will not fit. If you like Vortex brand optics, the Viper does fit the MR920.

    2. Jonathan Bangash says:

      The Vortex Venom can fit the MR920 with slight modification of the rear of the optic body with a Dremel tool. You need to shave off a small amount for it to fully line up with the MR920. I have it installed on mine and it worked with slight modification.

  10. CHARLES BEAVAN says:

    Is it possible to mount an Aimpoint Acro to this slide?

    1. Jessica Roe says:

      No, sorry that optic will not fit.

  11. Aron says:

    How about a Trijicon RMRcc? Being that the mounting holes do not align, I am trying to determine what mounting plate to use. Any suggestions?

    1. Jessica Roe says:

      We do not currently have a solution for the RMRcc. We have heard that Trijicon is coming out with an adapter plate, however we have not yet tested that as an option.

  12. Ryan says:

    Anyone run swampfox liberty with their MR920? I used spacer A and the number 1 screws. The head of the screws slightly cover the battery cover. Anyone know of a fix to this?

  13. Mick says:

    Can the 920 optic cut slide be fired without the optic mounted?

    1. Jessica Roe says:

      Yes, absolutely! We also offer a cover plate if you’d prefer not to mount an optic at all–you can find those here.

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