Options for Mounting Your Red Dot Sight

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If you’ve missed it, pistol-mounted optics (PMO), also known as red dots, are “here,” they are staying; they are not going away. So, how do you put one – or more – on your pistol(s)? There are several ways to mount that dot. Some work with a stock slide, then there is direct milling, Unity’s ATOM mount, which seemed to morph into Glock’s MOS, Smith & Wesson’s CORE, and similar systems from other manufacturers.

Before I get into details, the term footprint is one to address. It is more than just the length and width of the optic in question. It also considers the location of the mounting screws, how much contact (engagement) those screws need to secure the optic to the slide, and the placement of any backup sights. Unfortunately, there is no consensus on which footprints to standardize on – one for bolting into and one for clamping across.

The Insights MRDS is mounted to this Combat Elite with a dovetail mount.

Rear sight Dove Tail mounting

When the movement to get red dot sights (or Pistol Mounted Optics) onto slides first started, the way to it was by replacing the rear sight with a dovetail mount. It probably had to be fitted to the existing dovetail. The one in the 1911 photo above was from Burris to my recollection. The optic is an Insights Technologies MRDS. Counting the squares on the graph paper will give you an idea of the offset.

While I still use this style with my force-on-force pistol, I cannot recommend it for defensive use.

The direct mill mounting cut of a Trijicon RMR to a M&P 1.0

Direct Milling

The next option came on the scene quickly. Gunsmiths were milling pistol slides to accept optics being mounted directly to them. At first, it was only a few gunsmiths, but the list has grown significantly, so much so that I would not attempt to list them. Mark Housel (L&M Precision), now retired, cut my first M&P for a first-generation Trijicon RMR. Since then, I have had slides cut by Atei – for both Aimpoint Acros and another RMR – and Fink’s Custom Gunsmithing for Holosun optics.

Some gunsmiths will do this with a cut that accepts the general dimensions of the make and model; others want the specific optic so that they can cut the slide for the measurements of the individual optic. That work will involve differences of thousandths of an inch. Initially, I did not buy into this; however, with time and exposure, I see the benefit of doing it this way.

Based on the dimensions of both the optic and the slide, one may get the optic low enough in the slide for the stock sights to be used.

The direct mill method continues to be a solid choice regardless of whatever other methods emerge. And, as I will address later, manufacturers have their own versions of this now.

This optic-specific milling does limit you to one footprint per slide.

Unity’s Atom Mount conversion. This happens to be an uncommon version done to an M&P slide.

Unity Tactical

Unity’s ATOM mount is an intriguing design that preceded manufacturers’ first attempts at factory mounting. Rather than cutting the slide for the optic, which limits you to just that footprint, this style made one large dovetail-like cut in the slide between the breach face and the rear sight cut. They made plates for several different optics, all of which fit that one dovetail cut. The plates fit snuggly in that cut. Also, it is secured by one screw entering the slide from the left-hand side.

This was the only way, at the time, to mount an Aimpoint T-1 to a pistol. Five different plates are available, covering the Aimpoint Acro, Aimpoint T & H optics, Leupold Delta Point Pro, Trijicon RMR, and Vortex Venom & Viper optics. Commercially, you will only see these plates available for Glock pistols.

Unity had aftermarket slides made to fit Glock’s 3rd and 4th generation -17 and -19 pistols.

A tiny number of M&P pistols were converted to this mount. Unfortunately, it never went beyond beta testing.

At SHOT 2020, Unity displayed a gen 2 Atom that fits a broader spectrum of handguns. I’m eagerly awaiting the evolution of this design.

Unity Tactical’s second-generation Atom Mount from SHOT 2020.

Factory Options

Glock’s MOS and the CORE system from Smith & Wesson are well known, as is the Sig version. These are probably the most common method of mounting optics. There have been some concerns about factory plates and their fit.

A Steiner MPS mounted to a Glock 19 with Tango Down’s plate.

As a result, several aftermarket solutions have come to market. These include, but are not limited to, C&H Precision, Forward Control Designs, and Tango Down. I recently started to evaluate the Tango Down plate on a Glock 19 with a Steiner Optics MPS sight.

The beauty of the various plates is the ability to change between optics without regard to their footprints.

Other Factory Options

The Shadow Systems’ slides come cut for multiple footprints.

Shadow Systems makes an aftermarket Glock in the way that – for example – Springfield makes an aftermarket 1911 pistol. The Shadow System slide will accommodate different footprints without needing adapter plates. I ran a week-long class for twelve shooters with Shadow System pistols that all had Holosun optics. I won’t argue against that combination.

The M&P slide with the factory cut for the Acro – not available outside of government (PC: S&W)

Finally, we have gone nearly full circle with two manufacturers having slides factory cut for Aimpoint’s Acro P2 and P2 optic to be directly mounted to the slides. Unfortunately, as of this writing, neither Glock nor Smith & Wesson will sell them to the public.

No matter which option you choose, follow the manufacturer’s recommendation for mounting the optic.

There you are; there are many ways to mount your optic onto the pistol of your choice.