Red dot pistols have exploded in availability and variety over the last few years. Nearly every major firearms manufacturer offers a factory “optics ready” platform in their pistol lineup. Meanwhile, optics manufacturers continue to add to a dizzying array of pistol optics already available. As a result, those in the market for a red dot for their pistol frequently face this question: “What type of red dot fits my firearm?”
The answer to this question is both simple and complex. The simplest answer is it depends. In an effort to address this question, I’ll discuss some of the most common factors to consider for purchasing a pistol red dot that is compatible with your firearm.
Slide Cut
The slide, or “optics”, cut on a pistol is typically the cut on the pistol as provided by the manufacturer or from a custom source. The early days of pistol-mounted optics revolved around a frame-mounted platform, typically a Picatinny or Weaver mount, with a C-More or similar red dot reflex sight mounted to the rail. Over time, reflexive optics shrunk to the minimalist open-emitter designs that have become the industry standard. In the early days of minimalist footprint red dot optics, the most common options were either a Trijicon RMR or a Docter reflexive sight. Since pistol manufacturers didn’t offer an “optics ready” selection at the time, custom slide cuts were offered by a variety of aftermarket companies to mount those optics directly to the slide. The cuts offered by these aftermarket companies were specific to the footprint of the red dot it was cut for. As a result, these cuts were only compatible with that optic’s screw mounting configuration and footprint.
Since the early days of these custom optics cuts, manufacturers have followed suit by offering pistols with milled slide cuts that allow for the addition of a mounting plate. By doing this, manufacturers standardized their slide cut to fit a variety of different optics by simply swapping the mounting plate. Where custom cuts only allowed a specific optic configuration to be mounted to that pistol, the inclusion of a mounting plate opened the door to significantly more red dot options for the end user. However, each firearm manufacturer has a different system for mounting optics to their optics-ready selections, and it can vary greatly from one manufacturer to another.
Glock’s MOS system is one of the earliest factory options designed to direct mount an optic to a factory pistol. The system uses a mounting plate designed specifically for a particular optic’s footprint. Most manufacturers, except Springfield’s recent introduction of their Variable Interface System, use an optics mounting plate to adapt their optics cut slide to different pistol optics. The Variable Interface System is a recent introduction with the release of Springfield’s modular Echelon pistol lineup. While relatively new, it will be interesting to see how this affects the industry standard of using a mounting plate since Springfield’s design allows the optic to be mounted lower on the slide.
By deleting the need for a mounting plate, the optic is mounted lower on the slide. Traditionally, the addition of a mounting plate to mount an optic required the use of elevated or suppressor height sights if the end user wanted backup iron sights in the unfortunate event the optic was rendered inoperable.
Optic footprint and configuration
Unfortunately, there is little standardization amongst pistol and optics manufacturers. For example, an Aimpoint ACRO doesn’t have the same hole pattern or mounting configuration as a Trijicon RMR while a Vortex Viper or Venom is also different from those two options. Fortunately, there is some cross-compatibility among brands. For example, a Burris Fastfire (2, 3, and 4 variants) has the same footprint as the Vortex Viper and Venom.
If this already seems confusing, it’s understandable. There are dozens of pistol optics and optics-ready firearms available. The process of finding an optic that works for your firearm should start with identifying the slide cut on your firearm. If your pistol was custom-cut by a local gunsmith or aftermarket company besides the firearm’s manufacturer, you will need to identify your firearm’s specific optic cut. That firearm will only accept that optic footprint and may accept other brands that utilize that specific footprint. Gun Mag’s compatibility chart is an excellent guide to see what optics have compatible footprints and may work with your setup.
For slide cuts that are not from the firearm’s manufacturer, I strongly recommend using caution when considering mounting an optic that may be “compatible” but wasn’t the one the slide was cut for. I’ve seen slides cut for Trijicon RMR optics from some gunsmiths that wouldn’t fit anything else because of how tight (or in some cases, how poor) the tolerances were from the gunsmith who added the slide cut. In short, if your gun has an aftermarket cut for a specific optic, I recommend sticking with that optic unless a reputable gunsmith or company says they can adapt it for another optic brand or model.
If your firearm came from the manufacturer optics-ready, go to directly to the manufacturer to determine what mounting plates are available for their pistols. Those mounting plates are compatible with certain optics footprints and should be listed by the firearm’s manufacturer. Normally, the firearm manufacturer will provide you with a list of what plates work with what optics and, accordingly, what optics your pistol can use.
A Note About Custom Fit Optics
In the last few years, Holosun began manufacturing optics that mount directly to the slide of the firearm. Holosun’s SCS line is designed specifically for the optics-ready model firearm offered. While Holosun’s SCS is the only current offering to do this, it’s worth noting as the SCS will only mount to the make, and model it’s manufactured for. For instance, a Holosun SCS for a Glock 17 will not mount on an optics-ready Walther PPQ, Springfield, or otherwise. It’s designed solely for the Glock. The same goes for an SCS manufacturer for the optics-ready variants of the HK VP9.
For those who think “I can make it fit”, plan to be disappointed. Mounting an optic to a pistol is not a situation where the end user can make a round peg fit in a square hole. Be conservative about what you mount. When in doubt, try to verify its compatibility with both the optic manufacturer and the firearm manufacturer. If there is doubt, I recommend against it. The last thing you want to occur on a fighting pistol is to have the optic work its way loose or fly off under recoil or heavy use. This result is not ideal, especially if you’re in the fight for your life.
Final Thoughts
A fighting pistol with an optic is a tremendous boost to a shooter’s capability. Optics are not a replacement for the fundamentals of good trigger control, grip, stance, and sight picture – they are a complement to those skills and should be approached as such. When considering what optic to use, there are plenty of resources available from the firearm and optics manufacturer to help guide you toward what will work best with your intended use and needs for your pistol. As mentioned earlier, Gun Mag Warehouse has an excellent resource available to assist you with finding a suitable optic for your firearm. Once you’re set up, remember to get out and train. Happy shooting!
