Tips to Make Sure an Optic Fits Your Pistol

One size does not fit all when it comes to mounting a red-dot or reflex optic on a pistol. Bases on aftermarket units are not necessarily identical—so-called footprints—and the pattern milled into the slide of guns made to accept them varies by manufacturer, sometimes model. Adapters and plates remedy the conflict, but the number of incorrect combinations is dizzying. I contacted the experts and firearm and optics companies and asked for some tips to make sure the optic fits on your pistol. 

A semi-automatic pistol designed to accept an aftermarket red-dot sight has a combination of grooves, dimples or lugs milled into their slide. Its appearance, size and configuration are often company-specific, proprietary, and on only rare occasions mates perfectly with the footprint of popular aftermarket optics. Manufacturers that make handguns for that purpose address conflicting profiles by providing a selection of adapter plates. The approach is today’s most efficient method of mounting.

Tom Victa, pistol product manager for FN America explained (full interview here), “FN’s optics-ready FN 509s feature our patented Low-Profile Optics Mounting System, which has everything users need to mount most pistol red-dot optics straight out of the box, including a handy reference guide to tell you what MRD insert and screw set go with which optic.”

Smith & Wesson Senior Director of New Product Development Tony Miele said the company uses the Competition Optics Ready Equipment mounting system (you can read his complete explanation here). Purchase a C.O.R.E. model and, “Six mounting plates are supplied with the pistol that accommodate many of the popular optics for sale,” he said.

Glock cuts its slides for the company’s Modular Optic System. “We include an adapter set with every MOS [except Slimline models] that has four different plates to cover the vast majority of pistol optics offered,” according to my interview with PR and Communications Manager Brandie Collins. “If an optic does not fit, then the manufacturer typically provides an adequate plate. Slimline does not come with adapter plates and are specific to some of the new micro dots for narrow profile CCW pistols.”

Dimensional Analysis

The systems perform flawlessly at countless competitions annually and the advantages of lightning-fast target acquisition haven’t escaped the notice of self-defense enthusiasts. The setup is increasingly common on concealed carry guns. But which is best?

Each function flawlessly and come highly recommended by the experts. Victa, reminded that, “FN created the first factory red-dot pistol 15 years ago, so we know a few things about mounting red dots on pistols.” Most optics mount quickly and efficiently he said, and the company’s “… system allows for interchangeable steel recoil bosses and reduces overall height and weight for optimal performance.”

Collins added, “Glock is the number one selling pistol brand and has given a large focus on MOS.” There are 10 commercial models currently available.

Other Options?

You can also purchase a new slide or have a current one machined to anchor without adapter intervention. Rival Arms, a Texas-based firm with an enviable reputation for that service, explained by e-mail, “We offer two different optic cuts, RMR and DOC. The RMR cut, as you can imagine, is the same optic cut as the Trijicon RMR sight and will also work with other optics that follow this footprint (Trijicon SRO, Holosun 507c, Swampfox Kingslayer, TruGlo TRU-Tec Micro RMR variant, etc.). The DOC refers to Docter Optic footprint/set screw pattern, which is compatible with the following popular sights: Vortex Viper & Venom, Burris FastFire, etc.”

Optic-ready slides are available. “Currently we have three different footprints, the RMR, RMRCC and the Shield RMSC,” a Brownells gunsmith who asked to remain nameless responded. “The RMRCC and RMSC cuts are on the G43 and 48 slides. The RMR on 17, 19, 26 and 34 slides. Leupold DeltaPoint and Burris Fastfire are in the works and should be available second quarter [of this year].” As for which profile is currently most popular, he said the RMR because, “…there are other companies that use that footprint, so a person isn’t tied to a specific brand of optic.”

Failsafe Tips to Make Sure an Optic Fits Your Pistol

Regardless of your approach, the experts agree enthusiasts should check your preferred optic’s footprint, compare it to the slide cut or adapters provided and, when in doubt, contact customer service to ensure your purchase is the right one.

[This article originally appeared in NRA’s Shooting Illustrated magazine, and after deadline I received more information and here are links to comments provided by Leupold and Bushnell. Photo courtesy of Smith & Wesson.]

 —Guy J. Sagi has crafted the words and images that capture the spirit of the outdoor sports and beauty that surrounds them for magazines, websites and marketing materials for more than three decades.

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