red dot sights

A Brief Guide To Red Dot Sights: What They Are, How They Work, And You

The word is out: the red dot sight is the way of the future. Optics are au courant; iron sights are the past and we'd better all just get used to it.

What the heck are they, though?

Red dot sights are a form of what are called "reflex sights," which differ from traditional scopes. Here in this brief guide, we're going to briefly go over what they are, how they work, and also what you should know before taking the plunge on a red dot.

This is a good thing to consider before you put an optic on your Springfield Hellcat

A Red Dot Sight Is Nothing New - In Fact, They're Older Than Dirt!

reflector sight

The red dot sight, as with so much in the gun world, is actually nothing all. Just like how "appendix carry" is just the modern term for a "belly gun" (and appendix holsters existed a loooooooong time before Glocks; in fact, they existed before CARS were a serious thing) a red dot sight is just a new form of an old technology, that of what are called "reflex sights."

What is a reflex sight?

Simply put, a reflex sight - also called a reflector sight - projects an image in the sight picture, serving as a reticle or aiming point in the field of view. Since the sight is of fixed power, and is mounted over the barrel, the image is therefore "to infinity."

The reflector sight was actually invented for use with small arms by Howard Grubb, an Irish telescope maker and inventor, who also helped develop the periscope. Grubb devised an optic that the user looked straight through, but featured a small window on the top of the optic housing, with a bit of reflective material in it. A reflective piece of glass is located at an angle inside the housing, which projects the image of the reflective material on the front lens of the optic. As the user looks through it, they see the image projected out to infinity.

Grubb, correctly, surmised that an optic would make fast, accurate shooting easier than iron rifle or handgun sights, which is why a lot of people absolutely love using a red dot optic.

Okay, so picture a gun from a side view. The barrel is pointing to infinity in a straight line. The optic sits atop the barrel, with the reticle creating an image that extends to infinity as well.

reflex sight

Thus, as the gun's bore is brought up into alignment with your eye, so is the image (meaning the dot or reticle) in the optic. Since there's no focal plane to find, such as in a telescopic scope, it allows the user to quickly pick up a sight picture.

In other words, faster sight picture, faster on target, easier to use than a scope.

The price of this? Little to no magnification, so it's not the best at long range unless you have a wide field of view and have memorized your drop table.

How Does A Red Dot Optic Work?

A modern red dot optic shares much with Grubb's reflector sight from the start of the 20th century, but just adds a few bits of modern technology.

There were a number of different reflector optic designs that emerged over the years, with great disparity in how each specifically functioned. Instead of describing it in a bunch of detail that you don't care about, we're going to skip a lot of specifics for the sake of brevity to give you a basic picture of how reflector sights work.

You have two curved lenses, one at the front and one at the rear of the optic. In the case of a scope, they're at both ends of the tube and in the case of a the modern red dot pistol optic, they're close together, sort of like a double-pane window.

Now, how the optic works from there depends on whether it's a passive system - meaning solely powered by light - or an active system, which uses a power source. Bear in mind that some red dot sights for pistols aren't battery operated, so this is still something you want to know!

In the broadest strokes, a passive system has an image etched or inlaid into the glass, usually made of copper or some other reflective material. The image is either placed at the focal point of the front lens or - in the case of reflex optics with a scope housing - placed at an angle. In that arrangement, the angled lens projects and magnifies the image onto the focal plane and on or around the focal spot of the image, meaning the center of the optic.

Light enters the optic, causing the image to illuminate. Since the lenses are curved, the focal object - which is usually incredibly tiny in real life - is magnified and illuminated.

The effect, in short, is light goes in, causing the image to light up in the field of view.

But what if it's powered?

Oh, well in that case, it's even simpler! The power source activates, projecting a focal object into the focal point of the optic, meaning the center.

What A Red Dot Optic Does

red dot optic

The bottom line of red dot optic is this:

In either a classic reflector or reflex sight, or in a modern red dot sight, an image is projected onto the focal point of the optic, meaning the direct center of the scope.

Since the optic and therefore the image is fixed in place in relation to the receiver and barrel of the gun, the image moves with the gun. As you bring the top of the gun into alignment with your eye (as well as the target) the image comes into alignment as well. If you move the gun, the image moves.

The benefit?

The image, the dot or other reticle you see through the optic is the point of aim. Provided the optic is securely mounted and zeroed, where you put the dot is where the bullet will land as the image is projected out to infinity in the exact same direction as the muzzle.

In practical terms, this means that all you have to do to land the shot is get the dot where you want the bullet to land. This makes fast shots on target easier, and follow-up shots faster. People are catching on, which is why so many more pistols are now coming modified at the factory, with recent pistols like the IWI Masada, Springfield Hellcat, and others being ready to run out of the box.

Does this necessarily translate to more accuracy?!

Well…that actually gets a little complicated.

Pros And Cons Of Red Dot Sights

Nothing is perfect, of course, even red dot sights. Every type of optic comes with its pros and cons; almost everything relating to guns - heck, just about everything in life itself - comes down to choosing the set of downsides that you prefer to live with.

So, what are the upsides to red dot sights?

Faster sight acquisition for a start, and a better potential for accuracy. You can get aligned on target faster, and provided the optic is correctly zeroed, score more accurate hits (especially with pistols that have a shorter sight radius) and potentially out to longer distances.

In other words, they're a better sighting system than iron sights, in the broad strokes. That's why competitive shooters and militaries have been using them for years.

But what are the downsides?

For one, the potential for precision depends a lot on the size of the reticle. The larger the reticle, the less precision you'll be capable of as distance to the target increases; a 6 MOA dot is a 3-inch circle that you can't see on a target at 50 yards since the optic isn't magnified. The bigger the dot, the less potential for precision.

For two, the optic can break. Unlike scopes, which have a metal housing, the typical red dot sight is two lenses basically right up against each other under a metal arch. They can easily get broken, and replacing them is expensive if the manufacturer's warranty doesn't cover damage from use in the field.

Then you have the battery issue. While the typical red dot sight has a battery life measured in years, that's based on minimal usage; if yours is set to a higher brightness setting and you use it often, that's going to diminish the battery life. As a result, you'll want to change them regularly, with the interval depending on you, how you use it and so on. Some people change batteries weekly, so be prepared to do so.

Another downside, though this is rather minor, is the learning curve. You're going to need to invest time into zeroing the optic and then learning how to use it, which is going to take more than one trip to the range in all likelihood. They are not plug and play.

Red Dot Sight: Accuracy, Reticles, And You Need To Zero The Darn Thing!!!

red dot sight

Modern shooting aids including the red dot sight as well as laser sights are often misunderstood by the layperson. Both devices are used by a lot of people to enable their inherent laziness.

That's right, we said it: a lot of people buy a red dot or a laser because they're a LAZY SHOOTER.

Laser sights project a dot in low light, this is true...but what good does that do you if it has nothing to do with your point of impact? Oh, it's only a bit low and a bit right you say? Are you going to use Kentucky windage in the dark?!

Therefore, selecting and installing a red dot optic therefore depends a heck of a lot on what you're going to use it for.

So, red dot sights come with a variety of reticle shapes and sizes. The dot or triangle - the most common shapes - are measured in minutes of angle. What this means is that the farther away the target is, the larger the area the bullet will land in and therefore the larger the group will be. The smaller that dot, the harder it is to index quickly.

So, understand the application BEFORE you get an optic.

Do you anticipate using this pistol at short AND long range? If so, you want a medium size; 3 MOA would be a good balance between easier sight acquisition and long range accuracy. Remember, that means a 1.5-inch group at 50 yards (if you shoot perfectly!) and a 3-inch group at 100 yards, since 1 MOA is roughly 1 inch (it's 1.047 inches, but people who actually bring that up in conversation are people that nobody likes) at 100 yards.

If you're just looking for close, fast and nasty, get 5 MOA or larger. Get dot on target and make it go pew.

Popular makers offer a range of reticle sizes. Sig Sauer's ROMEO sights are offered with 3 MOA and 6 MOA reticles, Trijicon's RMR and SRO optics are offered in sizes ranging from 1 MOA to 13 MOA, Leupold's DeltaPoint Pro is offered in 2.5 MOA and 7.5 MOA, Aimpoint's Acro optics have a 3.5 MOA reticle, and so on and so forth.

For you folks who just bought a Springfield Hellcat and intend to add a Shield Sights RMSc optic, those are offered in 4 MOA and 8 MOA.

After installation, you will also need to zero the optic to point of impact, just as you need to zero a laser or a scope. This goes double for co-witnessing.

Red Dot Sight Features


There are some other red dot sight features that we will briefly go over. Again, this is a quick guide, rather than a comprehensive one. (That will come later!) If you're a complete newbie, this is where you learn a few of the basic bits that you're going to find on a red dot sight for pistols.

Batteries are located in a few different locations. They can be under the optic itself - meaning the optic has to be taken off the pistol for the battery to be changed - or the battery cover is on the top of the optic's housing. Opt for the latter as they are usually easier to change, unless you have no choice.

Some optics are dual-illuminated. This means there's a tritium/phosphorescent lamp that illuminates the sight window in the optic. This keeps the optic functional if the illumination system fails, and gives you greater visibility in low-light conditions. However, a drawback is that dual-illuminated sights tend to have larger reticles, meaning you're going to have problems finding one for long-range precision shooting.

Earlier, we mentioned co-witnessing. So here's how that works:

Co-witnessing is when you leave iron sights on the pistol, and align the reticle of the optic with the top of the sight posts. In other words, the idea is that if you're holding the pistol perfectly level and perfectly aligned with the target, the sights and the dot in the optic will be aligned as well.

If you're going to keep iron sights on the gun, this is a necessary step. A lot of people use night sights in conjunction with an optic, so there's a failsafe if the optic breaks or stops working. By zeroing the optic to the sights, your point of aim/point of impact doesn't change if the optic stops working.

Kinda smart, innit?

However, this typically requires installation of suppressor-height sights, so you'll likely need to dump some cash into your pistol. But it can pay dividends in faster and more competent shooting.

So that's a brief guide to how red dot sights work. Hopefully you've gotten an idea of what they're all about, and why they've gotten so popular.

About The Author

Writer sam hoober