How to Install the Gideon Optics Judge Reflex Sight

If you want faster target acquisition and improved accuracy from your firearm, you need to install a reflex sight you can count on. The Gideon Optics Judge sight gives you a feature-packed optic that doesn’t break the bank, making it a popular choice for RMSC-pattern pistol slides. These thinner handgun slides are a great choice for concealed carry, so we knew we needed to maximize the tactical benefit while keeping the footprint small. Let’s run through how to properly attach the judge and get your gun ready to shoot better.

For visual learners, check out our instructional video for a hands-on demonstration

Out of the Box

Inside the box, you’ll find everything you need to install your reflex sight on an RMSC pattern slide or a 1913 Picatinny rail. The Judge sight comes pre-attached to a low-profile Picatinny-type rail mount and includes a Torx Allen wrench sized to fit the included mounting screws and a waterproof gasket. Remove the optic from the mount by removing the two screws going through the top of the optic housing into the mount. On the underside of the optic, you’ll find a battery compartment that accepts a CR 2032 Lithiun-Ion battery. Snap it into place with the positive “flat” side facing out, and you’re ready to turn on your optic and verify it’s working. Verifying your optic wasn’t damaged in transit saves you the time of installing a reflex sight that needs support or replacement.

Mounting the Judge Using the Picatinny Mount

Our low-profile Picatinny mount makes it easy to install a reflex sight on compatible pistols and shotguns or as an off-set sight on a rifle or carbine. This versatile mounting system is one of the most popular among shooters and manufacturers, thanks to both its versatility and ubiquity. Our low-profile mount makes full use of both while keeping your optic tight to the weapon and out of the way when not in use.

1. Insert the Battery and Check Functionality – If this is your first time installing your reflex sight, you’ll have a fresh battery ready to go. If you’re moving the right from one weapon to another, now is a great time to give it some fresh juice.
2. Attach the Judge to the Mount – The judge is secured by two small screws that pass through the top of the housing to the mount. Apply a small amount of blue thread locker and hand tighten them for a stable mount.
3. Loosen the Screws on the Side of the Rail Mount – This will give you the play needed to slide the mount onto your weapon’s rail and position the screws in their channels.
4. Apply Forward Pressure as You Tighten the Mount Screws – While tightening the screws on the low-profile mount, apply a gentle but firm pressure to push the optic toward the muzzle, seating the screws as far forward in their channels as possible. This helps “pre-load” your optic mount to account for the forces of recoil acting against it as you fire.

How to Install Your Reflex Sight on a Slide

Installing the Judge on a compatible slide is straightforward and easy. We’ve engineered it for a precise fit that gives you a stable reflex optic you can trust to deliver accuracy and precision.

1. Insert the Battery and Check Your Optic – Power on the Judge and adjust its brightness up. Since you won’t be using the low-profile Picatinny mount, put the Picatinny mount screws back in the mount loosely to keep them safe and set the mount aside.
2. Verify Your Pistol is Unloded and Remove the Slide – Safety is always your first priority. Once you’ve ensured your weapon and its chamber are empty, remove the slide for easier installation.
3. Remove Your Sight Mount Cover Plate – If equipped, remove the sight mount cover plate on your slide, exposing the RMSC or Holosun K mount. These are largely similar, with the only difference being that the Holosun K mount deletes the back two recoil bosses.
4. Apply the Waterproof Gasket – Ensure the mount site on the slide is clean and free of grease or debris, then align the included waterproof gasket on the mounting surface. This helps keep moisture from entering the battery compartment or electronic components of your optic. 
5. Install the Reflex Sight – Press the Judge straight down onto the gasket with the mounting holes lined up with their counterparts on the slide. Do not try to slide or shimmy the optic into place, as this can dislodge the gasket. It is engineered to be pressed directly down onto the mount. Apply enough pressure to compress the gasket slightly, as this helps create a stronger barrier against moisture.
6. Use the Appropriate Mounting Screws to Secure Your Sight – The Judge sight comes with two sets of screws to help you install your reflex sight on a variety of weapons: M4x0.7mmx8.6mm and M4x0.7mmx10mm. Some weapons will require shorter screws, while others allow the longer 10mm screws for more thread engagement. Note: Slimline Glocks like the G48 and G43 can use a 10mm screw in the left mounting hole, but an 8.6mm screw should be used in the right-hand hole to avoid impinging the extractor spring and plunger channel, potentially binding up or damaging your weapon.
7. Tighten Your Mounting Screws – Mounting screws should be tightened to 10-15 inch-pounds of pressure. If you don’t have a small torque driver, tighten the screws using the short side of your Allen wrench until they are snug, then use the long side to apply additional leverage to take them just past snug to the point where moderate pressure will not tighten them further.

Hit the Range and Zero Your Optic

With the reflex sight installed, it’s time to sight it in. There should be minimal adjustments necessary from the factory settings, but both windage and elevation are adjustable at 1 MOA per click using a small flat screwdriver. Brightness adjustments are easily managed with the large buttons on either side of the housing. Once you’re zeroed, your gun is ready for action.

Get More From Your Gun

We’re glad to have you with us, shooting better with a quality sight we know you’ll enjoy shooting with. Please contact us with any questions, and don’t forget to sign up for our emails to get news about the latest products and promotions delivered to your inbox. Get fully-featured optics at a great price from Gideon Optics.