Pitfalls to Mounting Pistol Optics

Pitfalls to Mounting Pistol Optics
Photo by Yamil Sued

Red-dot sights (RDS) mounted on handguns are a big deal. Nearly every major handgun manufacturer makes provisions for them on their guns, and the few who do not are, undoubtedly, planning to. I suspect that RDS for handguns are one of the chief reasons SIG Sauer decided to start their Electro-Optics division, and I would not be surprised if it was a significant factor in Beretta’s decision to acquire Burris and Steiner.

Both manufacturers and enthusiasts have been coming up with creative ways to bolt dot sights onto their guns for quite a while now, and that resulted in an abominable variety of different footprints and mounting methods. Effectively, we are putting up with this mess for no good reason beyond historical and industrial inertia.

Since I do not foresee competing manufacturers coming together and standardizing any time soon, I will mostly focus on general mounting considerations that apply to most attachment patterns out there with some specific recommendations toward the end.

Co-­Witnessing

The most important part of this discussion is co-­witnessing with iron sights: Whether you should do it, how you should go about it and where the rear sight should reside when you do. I spent the better portion of the last several years retraining myself to be proficient with reflex sights on handguns. Here are some tips I picked up in the process.


If this is a handgun you will use in a dynamic situation, it should have co-­witnessed iron sights. Co-­witnessed iron sights are not the same thing as backup iron sights (BUIS). BUIS are there to deploy in case your primary sighting system fails, so they do not have to be always visible. In a dynamic situation, co-­witnessed sights have to be in front of your eyes every time you aim with the gun, regardless of whether you are using the aiming dot of your RDS or not.


Mounting Pistol Optics
The author recommends backup sights for any gun that lives depend on. (Photo by Yamil Sued)

Most red-­dot sight mounting methods that use the rear sight dovetails to secure the mounting base immediately fall out of contention. They do away with the rear sight, with the dot sight ending up sitting pretty high. Frankly, most of these are a little unstable, too.

I have one that replaces the rear sight with a small Picatinny rail that has a channel milled through the center to form a backup iron sight. This is basically a BUIS configuration.

I took this rig to a handgun class at the Front Sight Firearms Training Institute where we spent a lot of time getting presentation from the holster grooved in. I’ve taken that class multiple times, and I try to do it with different guns (and sometimes with different hands). This time around produced some interesting challenges that really made me pay attention. I ended up using this setup for testing durability of various reflex sights but not much else.

Dot Challenges

One interesting discovery I made was how precise our muscle memory really is. In this configuration, the sighting axis through the red-­dot sight is quite a bit higher than with the iron sights I spent the last 20 years practicing with. My presentation was off and adjustment took time. The lack of feedback was especially noticeable.


When you present the firearm from the holster and the dot is not immediately visible, there is no obvious indicator telling you which way you need to adjust your hold to see the dot. With irons, if the front and rear sights are misaligned, you can see in which direction you have to adjust. In principle, if you only use one gun and get used to it, and you only have a nicely controlled shooting position, practice makes perfect, but this is more trouble than it is worth.

The most humbling part was shooting while walking. That really did not work well for me with only a red-­dot sight. Yes, I know that competition shooters do this all the time, but they probably fire more rounds in a week than many casual shooters do in a year or more.

I did a ton of presentation drills with the gun set up to be red-­dot-sight-only, and it got better. However, as my muscle memory changed, I became noticeably slower and less precise under timed pressure with my other guns that were set up differently.


The obvious solution to this is that we should endeavor to set up dot-­equipped handguns so that the iron sights stay where they are. That way, all the muscle memory and visual memory you have developed over the years stays relevant.

Visual Clues

For my day job, I spend a lot of time dealing with images and with how human vision processes those images. For example, when presented with a photograph, we all (mostly, there are some cultural differences here) start looking at the picture from the same spot. Depending on how the picture is composed, the time it takes us to process the image and comprehend what we are seeing varies depending on the visual clues we get from a few particular spots in that image.

If that portion of the picture we look at first does not contain anything distinctive, we flounder a little, and it takes us quite a bit longer to comprehend what we are seeing. That also has an effect on what image we find pleasing. A good photographer will compose a picture so that there is a series of visual clues that lead from one to another.

That same general principle applies to getting a gun on target quickly. We use a combination of muscle memory and visual memory to quickly position it along the line of sight between the shooter’s dominant eye and the target. Ideally, your muscle memory should get the sights to pop up perfectly in front of you, but there is still some visual processing happening.

Mounting Pistol Optics
Co-witnessing sights and red dots ensures the shooter will always have a way to aim. (Photo by Yamil Sued)

We process an image sequentially, and the way it works with co-­witnessed sights and red-­dot sights is as follows: rear sight, front sight, red dot. The more you practice, the quicker you get to the part where your eye locates the red dot. It is important, however, to not be consciously looking for that aiming dot. Let your subconscious add it to the existing skill in target acquisition with iron sights. This way, you do not have to consciously unlearn anything and you still retain speed and proficiency if the red-­dot sight breaks or has a battery issue (that is increasingly uncommon, but it can happen).

Location Matters

Another thing that appears to make a difference is the location of the rear sight. There are a good number of companies offering a setup with the rear sight moved to being just in front of the red-­dot sight. It has a cool look to it, and I have heard a variety of reasons why it is a superior approach. But, there is a good reason why it is not a superior approach, and I think it trumps all others.

If you are only going to have one gun, you can get used to most things. However, if you have been shooting for a while or simply have a variety of firearms, you are very much used to seeing that rear sight all the way at the back of the slide. Once again, this is where that pesky visual memory comes in. When you raise the gun into your line of sight, your eye first looks for the rear sight in a place where it is trained to look for it – at the back of the slide.

Both sight pictures are perfectly viable, but they are not the same, and transitioning from one to another costs time. I suppose the moral here is to pick a mounting method and stick with it. Personally, I’d lean toward keeping the rear sight where it belongs.

Sight Height

Let’s explore iron-­sight height a little further. Bore axis and how high it is with respect to the grip is mentioned a fair bit, since it affects perceived recoil and recovery. However, the offset between the grip and the sighting axis does not get any coverage worth mentioning.

Mounting Pistol Optics
Photo by Yamil Sued

Admittedly, when switching from handgun to handgun, grip angle and recoil control are arguably more important things to worry about, but sight location also matters. When we present the gun from the holster, our muscle memory takes it to a spot where the irons are supposed to be on our line of sight, and even a small difference in sight height will require retraining.

This is where red-­dot sight mounting methods become important again. With conventional reflex sights and “minimal gunsmithing” mounting methods, you have to go to tall suppressor-­height sights which challenge both muscle memory and visual memory.

After a ton of experimentation, I ended up using low-­ to medium-­height iron sights, and with the Shield Sights’ RMSc red dot I favor, there is a lot of latitude with how I mount these to the slide. These are the lowest profile sights currently on the market, and they have an integrated rear notch.

On guns where I have no space for a separate rear sight (like on a Smith & Wesson revolver), that notch is the rear sight. On my Glocks, I can mount a Shield RMSc just low enough for that integrated notch to not interfere.

Regardless of the brand, have a competent gunsmith cut the slide for your RDS. That way, you can make sure that the violent movement of the slide will not stress the two small mounting screws that hold most reflex sights in place.

If you end up with one takeaway from all this, it is the following: Do not assume that you can simply slap a RDS on your handgun and become faster. Some retraining will have to happen, and you will have to make sure that as you develop new muscle memory, you do not stray too far from muscle and visual memory you have been developing up to now. Make intelligent decisions and go train.

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