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A Primer on AR15 Optics: The Red Dot Sight Guide

With your first AR15 purchased, it won’t be long before you start looking at upgrades. The best red dot sight for your needs might be a poor choice for someone else. There are a variety of styles that you can choose from and I have put together a guide to point you in the right direction. I have a strong urge to tell you before you choose any upgrade to 1) save up for decent upgrades over junk, and 2) to make your first upgrade a reliable optic, be it a red dot or otherwise.

Red Dot Sights

The red dot sight has become a common choice for a first upgrade and often the low-cost of entry makes it very attractive. A red dot sight has a red (or green) circle of various sizes and the dot (or chevron) is placed on the target and the weapon is fired. With the red dot sight, we have multiple technologies in place ranging from fiber optics to holographic reticles. The first step is to choose a dot size and shape that will best fit your uses.

Dot Size, Dot Pattern

Choosing the wrong reticle for your use can be a hindrance. Making the proper choice of dot size and shape is dependent on your uses. Too small a dot and it won’t be as quick to pick up by the eye. Too large a dot and the dot can obscure your target if you are shooting at longer distances. Some red dot sights attempt to fix this issue by allowing a large circle dot reticle where there is a large ring with a precision dot in the center.The Eotech reticle is a perfect example. Deciding what dot to choose is the first step, and it is important to pick something that will suit your uses.

A simple 4 MOA dot will suit a general purpose rifle well. It is small enough to allow precision at medium range distances and large enough to be quickly picked up by the eye. Be wary of products that allow you to switch reticle patterns. These products have a reputation of being UN-reliable or often on the cheaper side of things. Introducing a product that allows you to change reticles means you might be introducing the potential for more things to go wrong. There are exceptions, however: Lucid red dot sights are getting generally favorable reviews and feature a user changeable reticle.

Using the Dot Size to Estimate Range

A red dot is also useful for rough estimation of range. Choosing a red dot with the right size can help with basic distance and holdover estimates. It’s not as simple as just choosing a dot! With the right holdovers and good distance estimates, you can score hits with a red dot easily to 400 yards on a man sized target. I whipped up the chart below to evaluate dot size for ranging estimates. Blue = distance where the dot starts to obscure the head Red = distance where the dot is roughly shoulder width Ammo: 55 grain 5.56×45 at 3240 FPS with a 50 yard zero

Yards	5.56×45	2 MOA	3.5 MOA	4 MOA	7 MOA
100	0.9	2	3.5	4	7
150	1.1	3	5.25	6	10.5
200	0	4	7	8	14
250	-2.4	5	8.75	10	17.5
300	-6.4	6	10.5	12	21
350	-12.3	7	12.25	14	24.5
400	-20.4	8	14	16	28
450	-30.9	9	15.75	18	31.5
500	-44.3	10	17.5	20	35

For more information on ranging with red dots click here.

Positioning the Red Dot Sight

Red dot sights can have a tube effect if positioned too close to the eye. Best practice is to place the optic further from the eye to mitigate the effect and shoot with both eyes open. Certain red dot sights lack a tube or have a very short “tube” and thus there is less area occluded by the body of the optic. Any “tube effect” can be negated by placing the optic further away from the eye. One thing of note is that the bigger the lens the more the dot can move around the viewing area. Quality red dots are parallax free after a specified distance which means the dot can be anywhere in the viewing area and your shots will still hit the target. This is helpful when shooting from unconventional positions. The dot does not need to be centered in the glass.

Battery Free vs Electronic

Often discussed are SHTF type optics. Inevitably “reflex style” battery free optics are discussed. Reflex style sights have no electronics to fail, and often these items are illuminated with tritium to give them low light function. The Achilles heel of these type of optics are that they can wash out in various lighting conditions with no way of increasing the dot intensity manually. If you want to run a system without batteries, you must also consider setting up your weapon to accommodate the deficiencies of reflex style sights. I would suggest constantly deployed irons to give you something to aim with should the dot wash out.

Electronic red dot sights are becoming more efficient and reliable as time goes on. At the highest levels of quality there is patented technology that allows the Aimpoint CompM4 to run for 8 years of continuous use. From there, the various models available will range from thousands and thousands of hours to hundreds of hours. The technology packed into red dot optics are constantly improving in durability and longevity. It is a constant point of argument that higher quality electronic red dot sights are so reliable that the benefits of fiber optic powered models are a moot point.

Micro Red Dots

The trend for red dot sights to shrink in size has continued. The leader of the pack, the Aimpoint H1 and T1, are very small and light units. Overall the viewing area is smaller, but if you are shooting both eyes open the size of the window does not impact performance. If you want to run a lighter setup and don’t mind obtaining some coin sized batteries, consider some of the smaller red dot products. The lighter weight and small form factor will give you a less bulky weapon. Some other models to look at are the Trijicon RMR and Eotech’s MRDS.

Should You Purchase a Red Dot or Go For Magnification?

A red dot optic is a common choice for your first upgrade to the AR15.  A red dot will help your shooting improve by giving you a great visual aid that is faster than iron sights and can be used more precisely with less eye strain. Remember that a 2MOA dot is *far* smaller than the width of the front sight post on your AR15. The red dots can be used at the very least with as much precision as iron sights inside of defensive ranges.

One of the great advantages of red dots over low power or variable power optics is costs. I prefer a bit of zoom, but a quality optic will cost more than a quality red dot and the red dot optics have a weight advantage over low magnification scopes. If your primary concern is  a 0-300 yard defensive range, a red dot should suffice well for this role. One way to add versatility (and weight) to your red dot sight is to add a magnifier.  Magnifiers can be added on as a later addition to give your red dot a bit of magnification.

Such a setup is a versatile “compromise” system. Not as clean as say a 1-4x variable, nor will it weigh less than an 4x ACOG setup, but it does give the option of adding or removing the magnification as needed. There is no perfect setup, so you need to balance your shooting needs with a system that will meet your goals.

Wrapping Up

A red dot scope / optic is a great first upgrade. Remember that your AR15 is a very accurate machine. As a defensive rifle it will do its part to get rounds on target. Buying a red dot scope to augment your ability to quickly acquire and fire upon the target is an excellent first upgrade. The wide variety of models and design goals means you should choose a system carefully based on your shooting goals. A quality red dot will give you a precise aiming point that is both faster than iron sights and (depending on dot size) more precise than irons as well. Save your money and go for a quality system and you will be quite happy with its durability and performance.