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How To Mount a Prism Scope on Your Rifle

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Prism scopes are among the most popular optic variants available. Their lightweight and compact form factor make them an excellent choice for a wide variety of shooting sports and activities, including hunting, competition, and personal defense. If you’re unfamiliar with this optic type, our article on what prism scopes are will round out your knowledge  

Just like any optic, though, it’s useless unless it’s mounted to your rifle properly. Achieving the correct mount height and eye relief distance is crucial for optimal performance. If you’re new to running optics on your rifles or new to rifles entirely, you may not know the process. 

We’re here to fix that. For most prism optics, mounting it to your rifle is incredibly easy, and we’re going to walk you through the process.  


Mount Height 

Your mount height is more important than you might initially assume. The mount height determines where the optic will sit when mounted on your rifle, which affects your cheek weld. This can be very important depending on what rifle you’re using. An AK, for example, has a much lower stock than an AR-15, so mount height that feels comfortable on an AR may be too tall for a traditional AK. Ultimately, the ideal height will depend heavily on your rifle, the eyebox of the optic, and your own physical stature.  

Prism sights usually come with varying-height mounts, but personal preferences may differ. Fortunately, most optic mounts are interchangeable and able to be adjusted. For instance, the Primary Arms SLx® MicroPrism™ scopes comes with a mount that offers 8 different mounting positions out of the box, but this optic is also compatible with aftermarket mounts that use the same footprint. It’s also compatible with special-purpose 3rd party mounts like the Unity Tactical FAST Mount with an ultra-high 2.26-inch centerline.  

Likewise, the Spitfire series of optics from Vortex uses an Aimpoint Micro footprint, making them compatible with any mount that utilizes that footprint. This gives you a lot of versatility if you aren’t a fan of the factory mount.  

Many newcomers often make the mistake of choosing the wrong mount for their optic. It’s important to make sure that you’re choosing the right one if you plan on swapping out. Check manufacturer websites and product manuals to be certain of your optic’s mounting footprint. 

Keep in mind that you don’t always need to purchase an aftermarket mount to get the height you desire. Optic risers are available for select prism scopes that raise the height of your optic without forcing you to buy another mount. One such riser is our MicroPrism™ Straight Riser. In many cases, your optic will come with a number of risers out of the box, so always check to see what’s included with the optic before you purchase an aftermarket mount. 

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Types of Mounts 

Just like how there are many types of optics available on the market, there are a lot of different optic mounts. We covered how important mount height is, but some optics use entirely different mounting systems. For example, scopes traditionally use scope rings and one-piece mounts, while red dot sights use their own proprietary mounts.  

Fortunately, most prism optics adhere to two mostly standardized footprints, or in some cases, adopt red dot-style mounts. Full-size prism scopes like our original SLx 3×32 and 5×36 prism scopes use the traditional full-size footprint, while miniature prisms like our MicroPrism series use the mini-prism footprint. 

Almost all prism scope mounts will be designed to fit 1913 rails, but within that category, you have QD-style and fixed-style mounts. QD (quick detach) mounts usually have tensioning levers that allow you to quickly attach and detach the optic while maintaining zero. These mounts tend to be more expensive, but they’re great if you want to swap optics around regularly. On the other hand, fixed mounts are more affordable, and in many cases, offer much higher torque specs to retain zero through shock. 

Now matter which style you choose, you can’t go wrong. Just be sure it matches the footprint of your optic! 

COM Unity Tactical Optic Mount

Mount Installation Process 

After you’ve chosen the right mount for your prism scope, you’re ready to install it. Prism scope mounts, in most cases, are removable via screws on the bottom of the optic that hold the mount in place. Most prism scopes come with a dedicated hex key wrench or a hand tool with the correct bit size. This tool is used to remove the screws that hold the mount to the optic.  

With your mount off, you can replace it with your new one. Depending on which mount you use, it may come with new screws to use in place of the stock ones. Always use the mounting hardware that comes with the new mount; they’re often spec’d specifically for the newer mount, so using the old ones likely won’t hold it securely to the optic.  

We recommend that you degrease your mount, apply a medium strength thread-locker to the new mount screws. This will ensure that the screws don’t back out when using your rifle, keeping it securely attached to your mount. 

Always refer to the optic manual when installing the mount. It may contain recommended torque values, which you should follow. 

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Mounting your Prism Scope 

Now we’re getting to the fun part, securely mounting your optic to your rifle. Before you do any work to your rifle, remove the magazine and check both visually and physically that it has an empty chamber.  

Next, place the optic onto the picatinny rail of your rifle. With it sitting in place, you can tighten the picatinny mounting screw to briefly hold it in place to check to see it’s sitting at a good distance for you. If the optic is too close or too far away from you, it won’t have the proper eye-relief necessary for use. Adjust its placement if necessary. 

Once you’ve found the right placement for your optic, you can remove the picatinny mounting screw, degrease it, apply a thread locker to it, and reinstall it into the mount. We always recommend you refer to the optic or mount manual to find torque specs, as over-torquing a mount can damage its reliability.  

After this, repeat the process to any other mounting screws if your mount has them, and you’re done. Prism scopes are among some of the simplest optics to mount onto rifles. Their simplicity is akin to that of a red dot sight, making it them just as easy to properly mount.  

Unlike a variable power optic, there isn’t a need to use scope rings or other mounting hardware besides the factory mount. Additionally, when the optic is secured properly to the mount, you don’t have to use a bubble level to check its placement. Instead, all you must do is check to ensure that the optic is securely affixed to the mount, and the mount to the picatinny rail.  

If you’re considering changing to an LPVO in the future, our guide on prism scopes vs. LPVOs puts both popular variants in a head-to-head comparison and will help you make a well-informed decision. 

Frequently Asked Questions 

Q. What is the ideal distance between my eye and the prism scope? 

A. Depending on the prism scope model you choose, it varies. For instance, our SLx 1x MicroPrism™ scope has a usable eye relief range of 2 to 6 inches. That said, the best eye relief for an optimal field of view is at 3.6 inches. As you increase the magnification, the eyebox, and optimal eye relief becomes more restrictive. As such, our SLx 3x MicroPrism™ and SLx 5x MicroPrism™ have a 2.7-inch eye relief.  

If you don’t know whether or not you should use a magnified optic, we recommend checking out our guide on prism scope magnification. It goes in depth on the different magnification levels available and the best use cases for each one.  

Q. Can you use the same mount for different firearms?  

A. Yes, to an extent. For prism scopes, most, if not all, attach to rifles via picatinny rails. So long as your optic mounts to a picatinny rail surface, you can attach it to any rifle that uses such.  

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Q. Are there any specific considerations for mounting a prism scope on an AR-15?  

A. Yes. Depending on if you’re running other optic accessories like IR-Lasers and Night Vision, you’ll want to make sure that your optic’s height is tall enough to work with your NODs. If they sit too low, you won’t be able to get a proper sight picture.  

Q. How can I ensure the mount stays secure when subjected to recoil?  

A. The best way to ensure the mount stays secure is to have a thread-locker applied to all the mounting screws, and to have each torqued down to the manufacturer’s specifications. Doing so will keep everything tight and secure, even when you’re in adverse conditions or firing several rounds in quick succession. Just be sure to use a milder threadlocker—the high strength compounds will make it very, very difficult to remove your optic. Blue Loctite is generally the most popular option. 

Desert Tech SBR wide 1101


Mounting a prism scope to your AR-15 or other rifles isn’t necessarily the most difficult task, but there a lot of steps you can take to ensure that your optic will last a long time and be compatible with your other accessories.  

Oftentimes, enthusiasts will overlook the importance of prep work and using other mounts. Other mounts may provide you with better benefits than the stock ones that come with the optic, and properly degreasing and securing your mounting screws goes a long way in maintaining the integrity of your optic.  

While you don’t necessarily have to do the prep work, it only takes a short amount of time and is only beneficial. So, in our eyes, it’s definitely worth it.