How To Mount A Pistol Red Dot: Expert Guide

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This past month I had an opportunity to attend a writer event at Gunsite dealing solely with the use of red dots on carry guns. Gunsite is the oldest and largest privately-run firearms facility in the world (3,200 acres, coming up on 50 years in business), and has been enjoying record enrollment. Their entry-level pistol course, the five-day Gunsite 250 class, is the standard against which all other basic defensive pistol courses are judged. Talking to the cadre at Gunsite this past visit, they told me that fully 40–50% of the students in their 250 course were using pistols with mounted red dots. They have amassed a huge amount of knowledge, not just on how to employ red dot optics on carry guns but on the mounting of them—and that last issue is what I want to cover in this column. In the past year, the Gunsite gunsmithy has only had to deal with perhaps half a dozen optics which have failed…but nearly half of all 250 students running red dots experience problems. Not with the optics themselves, but their mounting systems, the plates and screws. Which was completely unexpected information to me—that modern optics have gotten so good that they’re rarely breaking, and it’s incorrect mounting which is causing the lion’s share of problems.

Dave Fink runs the gunsmithy at Gunsite, and he gave a little red dot clinic to the attendees, explaining the most common problems he’d seen, and how to fix them. Mounting optics directly to a pistol’s slide is the best option. Some pistols are set up for this, and for those that aren’t, Fink and his people do a lot of slide cutting to direct mount various optics. The other mounting alternative is some sort of plate, and the most common one seen at Gunsite is the Glock MOS plate system. Not only are Glocks the most common pistol type now seen at Gunsite classes, the new Gunsite Service Pistol is a Glock—a Glock 45 with a Holosun 509 direct mounted to the side, with tall backup sights. In fact, I ran a Gunsite Glock during the three-day class. With the Glock MOS mounting system, the adapter plate is secured to the slide with two screws, and the optic is secured to the plate with two additional screws.

Whether you’re direct mounting or using a plate, all of your screws and screw holes should be clean of oil and old Loctite. Fink recommends either using heat to draw it out (he demonstrated with a little propane torch) or brake cleaner to remove the oil. Acetone removes old Loctite from screw threads. Q-Tips are invaluable for all of this. When you use Loctite, you want fresh Loctite bonding to clean dry metal. Sometimes the screws provided are a little too long, and go through the MOS plate and press against the top of the slide. This can warp your plate. One quick way to check this is to mount the optic to the plate when it is off the gun, and see if the screws stick out the bottom of the plate. If they do, a quick bit of file work will fix that problem.

Not tight enough and your screws can loosen and fly away. Too tight and you can shear off screws or even buckle optic housings. Fink recommends using a torque wrench for your optic screws, tightening the MOS plate screws to 18–24 in-lbs., and the screws holding the optic to the plate (or the slide in direct-mount situations) to 18 in-lbs. He recommends red Loctite for the MOS plate screws, and blue Loctite for the optic screws. Another useful trick is witness marks on your optic screws, drawing a line across the screw and onto the housing. Glancing at those marks from time to time will tell you if your screws are loosening.

The Glock factory MOS plates often leave a little gap at the front or rear of the optic, between it and the slide, increasing the recoil forces. Fink recommends, and uses, improved aftermarket plates from DPP Titanium and C&H Precision (chpws.com) which have spacers that act as additional recoil lugs. The C&H plates are FBI approved for their duty pistols. As for which optics they see most often at Gunsite, the Trijicon RMR footprint is the most popular, and the three most popular brands are Holosun (many of which use the RMR footprint), Trijicon, and Aimpoint. They have yet to see a brand or model of optic that doesn’t eventually break, but these seem to be the top performers. Bob Radecki of Glock was present at the event, and he stated that 70% of the guns they sell to law enforcement are MOS models, or packages that include an optic, indicating red dots are very popular and growing ever more so. One final tip—most lenses are secured to their housings with some sort of glue. When you’re cleaning your lenses, use just a Q-Tip wet with water. Some solvents can damage your optic, either removing the coating on your lens or eating away at the glue holding the lens to the housing.

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