These types of sights feature an illuminated "red dot" that functions as an accurate aim point for the operator. A red-dot sight is primarily meant for targets within 100 yards, but it can also work for longer ranges.
How Does a Red-Dot Sight Work?
The red-dot sight is often known as a reflex sight, which is a term stemming from the fact that red dots rely on non-magnifying reflectors to display the red dot. Basically, a small LED generates a colored dot of light, which reflects against a small spherical mirror. The mirror focuses the dot onto a lens, which is what you see when you look through the sight.
On more advanced (and expensive) red-dot sights, additional lenses may be added to the setup to eliminate "parallax". What is parallax? It refers to changes in the position of the dot when you look at it from different angles.
For example - you put your gun in a vise with the red-dot sighted right on your target's bulls-eye. When if you move your head to a different angle and look through the sight, is the dot still on the bulls-eye? Hopefully the answer is yes - that means that your red-dot is "parallax-free". This enhances the overall accuracy and usability of the sight. But be prepared to pay a little extra for a truly parallax-free sight!
Different Types of Red-dot Sights
Red-dots come in many shapes and sizes. "Tube" style sights look a lot like a scope, while "open" style sights are more of a square shape (Eotech sights are a good example of this).
The dot size, dot pattern, and dot color are some of the important considerations in choosing the right red-dot sight for you. You are the operator so your eyes, usage, the mission package and the configuration of your AR-15 would come into play in choosing your red-dot sight.
The dot size should be big enough for you to easily see, but not too large to obscure targets. Dot size is typically measured in MOA ("minutes of angle"). Essentially, 1 MOA means roughly 1" at 100 yards. So if you have a 5 MOA dot, that means this dot covers a 5" area on a target 100 yards away. For a general use AR-15 sight, we recommend MOA between 1 and 4 MOA. Anything larger than 4 MOA will just get in the way.
The dot pattern (AKA the reticle) is largely personal preference. Most sights have a dot (hence the name red-dot), but you can also get reticles shaped like crosshairs, or many other patterns. Some sights have adjustable reticles, and allow you to quickly switch between different reticle styles.
The last main choice is the color of the dot.
Wait - it's a red-dot sight so the dot is going to be red, right?
Not necessarily - green and blue are also available. From our experience, red is the best all-around color, but blue can be easier to see in certain bright-light conditions. It's best to try a couple of different sights and see what you prefer.
Scopes vs Red-dot Sights for AR-15
For a sight that works well on shorter-range shooting (less than 300 yards), the red-dot sight can be a great choice. They typically weigh less than a scope and are much better for quick target acquisition. Also, there will be no "tube effect" that is typical with a scope (due to the varying eye relief on scopes). Basically, a red-dot is much simpler to use but lacks the magnification of a scope.
If you want some magnification, one option is to get a flip-up magnifier that goes behind your red dot. This allows you to quickly magnify your red dot for long distance shots. Despite that added weight, this is a versatile option that is worth looking into.
Perhaps the biggest downside of a red-dot sight is that it requires batteries. No batteries, no dot! But on most red-dots, batteries last so long it's not an issue. For example, on the AT3 RD-50 Red Dot Sight, the battery lasts up to 50,000 hours between replacements.
Best Red-dot Sights for AR-15
There are many choices available for red-dots, and everyone seems to have an opinion on the best reflex sight for AR15. But we have 3 categories of recommendations: Best Value, Best Overall, and Other Excellent Red Dot Sights.
Best Value Red-Dot Sight for AR-15: The AT3 RD-50 Micro Red Dot Sight
Want a great red-dot sight on a budget? The AT3 RD-50 Micro Red Dot Sight is the best choice for a red-dot sight under $100. Think of this sight as the Aimpoint's little brother - tough, lightweight, and easy to use, at less than 1/5 the price. Some key features are a waterproof, scratch resistant body, clear multi-coated lenses, and up to 50,000hr of battery life.
One of the best features of the RD-50 Red Dot Sight is the available riser mounts. There are 2 mounts available – a medium riser for “absolute” cowitness with AR iron sights, and a high riser for lower 1/3 cowitness. Even with the riser mount installed, the sight is only 7oz - you'll barely notice when carrying your weapon.
If you want a red dot sight that is dependable and accurate but won’t break the bank, you cannot go wrong with the RD-50.
Best Overall Red-Dot Sight for AR-15: The Trijicon MRO Red Dot Sight
Launched in 2015, the MRO (Miniature Rifle Optic) is a relative newcomer to the red dot space. But we believe that the quality, functionality, durability, and decent price (under $500) of the MRO puts it ahead of the competition, and it’s our top overall red dot sight.
Trijicon is best known for their legendary ACOG rifle scopes, which have been the go-to military optic for mid-range applications for over 20 years.
The Trijcon MRO red dot sight packs many of the best features of the ACOG into a small red-dot sight. The forged aircraft-grade housing is as durable as you’ll find, and even waterproof up to 100 ft. The glass quality is superb, with exceptional clarity and a crisp red dot reticle. The MRO offers 3 choices of mounts – low, medium, and high - with the medium and high mounts designed for co-witness on AR-15.
Other Excellent Red Dot Sights
EOTech is a premier manufacturer of Holographic Red Dot Sights that allow heads-up, 2-eyes-open shooting. EOTech sights come in many different styles and reticles, some of which are made for specific calibers like .223, .308, and .300 Blackout.
What makes the EOTech sights so great? For one, they are reliable - these sights are used extensively in combat and law enforcement. They also have excellent low-parallax optics, and unique rectangle-shaped lenses for a wide field of view. Many of the EOTech red-dot sights are also night-vision compatible.
In 2015, EOtech’s parent company lost a fraud lawsuit, where they were implicated in knowingly selling defective sights to the US military and government agencies. The company recalled many red dot sights after this, and they say they have since addressed the issues, but this incident damaged EOtech’s reputation in the firearms community.
Now that these issues are addressed, we think that EOtech sights are still an excellent choice. Want to learn more about EOTech sights? Check out our selection guide and comparison chart.
Aimpoint is a Swedish optics company that makes red dot sights for civilian, police and military use. It is Aimpoint’s belief that a weapon sight should simplify aiming while performing reliably under the toughest conditions. And they most certainly succeed in that.
Aimpoint sights are regarded by many as the best sights on the market – and for good reason – they are nearly indestructible red dot sights with excellent battery life. Aimpoint sights are pricy, and the functionality is fairly basic, but you cannot go wrong with an Aimpoint.