The red dot sight is extremely compatible with AR-15s and other Modern Sporting Rifles (MSR) and is the optic of choice for most MSR owners. These sights are the fastest way to get on target accurately and for AR shooters, this is exactly what we need. Unless you are precision shooting at longer ranges, fast target acquisition and a shot that hits where you aim are all you need in competition shooting, plinking, home defense and even predator and varmint hunting. The reflex or red dot sight is the way to go for close quarters (CQB) to medium ranges, where speed is your top priority.
Before we continue, we need to get something straight—a “red dot sight” has become the term most use when referring to a non-magnified electronic sight that projects an illuminated dot (or other shapes) reticle on a target. However, the term is used incorrectly.
Both open and tube sights are reflex sights, but an open reflex sight is technically not a red dot sight.
Now, most people aren’t going to make fun of you if you refer to either as a red dot sight and will know exactly what you’re talking about, but since we (Sightmark) make both reflex and red dot sights, we’re nerdy about them and use the correct terms.
Open and tube reflex sights operate the same way. This is how they are set apart from holographic and prismatic sights—which aren’t actually red dot or reflex sights at all.
Reflex sights are called so because of the way they work. They work by using a reflective glass lens to align light from an LED to project an aiming point on a glass objective lens. Due to a special reflective coating on the lens, the illuminated red dot is visible only to you and does not go through the other side of the lens. The dot is never actually projected on the target, it only appears that way to the viewer.
The internal operation is the same for tube red dot and reflex sights; however, when you put a tube red dot sight and a reflex sight next to each other (as shown above,) they look nothing alike. Both are excellent optics with very few disadvantages, yet they do have slightly different specs and features that might make you prefer one over the other.
Reflex and tube dot sights are non-magnified (as mentioned above,) have an unlimited eye relief—meaning you can mount it anywhere along your rail without the worry of scope bite—and work on the Bindon Aiming Concept, meaning you shoot using the sight with both eyes open.
One of the biggest differences between a reflex/open sight and a red dot is the field of view. Reflex sights, due to their heads-up display (HUD) design allow for a wider field of view. The field of view is how much of the image you can see in the window or objective lens. Reflex sights let you clearly see the target as well as what’s around it, giving you a tactical advantage by allowing you to retain your situational awareness.
Reflex sights are also just a hair faster at target acquisition because the dot isn’t as confined in the head’s up display as in the tube style. Some might find, especially competitors or those hunting birds, that peripheral vision is obstructed or limited using a tube red dot sight when transitioning targets.
Reflex sights are more susceptible to the elements, though. Red dots have an enclosed housing protecting the internals. Also, reflex sights have an exposed light path so if anything blocks that path, you lose the reticle. To compensate for this, we’ve added an extendable hood on our new M-Spec reflex sight to help reduce the risk of losing your reticle.
Where the tube red dot has the reflex beat is how bright the reticle is compared with reticles on open sights.
For which one is better, I can’t tell you. Our military uses both tube and open sights, so both have their place. Depending on your usage and firearm, you will find that you prefer one over the other. As a general rule, most people put a tube red dot on their shotguns, a mini reflex sight on their handguns and either on their AR-15.