One of the most popular accessories for the AR (and other MSRs) is the red dot or reflex sight. And for good reason…they help you get on target quickly for accurate shot placement in competition and in self-defense and tactical situations. In fact, I’m betting it’s probably one of the first things you’re considering adding to your new build.
There are a lot of different reflex sights to choose from. But regardless, whether you decide to go with an open reflex sight or closed tube red dot sight, mounting either optic is the same.
Fortunately, reflex sights don’t require much of a learning curve to master. They don’t magnify, so there’s no adjusting for distance. It’s pretty much mount, zero and go.
Unlike traditional riflescopes, reflex sights have an unlimited eye relief, so there is no right or wrong place to mount your sight. Further, your target and your dot stay the same size no matter where you put your sight on your rifle. Technically, you can put it anywhere along the rail your little heart desires. With that being said, most people strongly suggest you keep it mounted on the receiver part of the rail and not the handguard part of the rail. Now, there are placements that might raise a few eyebrows—like as close to the barrel as possible—but don’t worry, you aren’t going to look like a tool even if your sight is in the most extreme-forward position. As Ryan Gresham points out the video below, Scout rifle (without free-float rails) shooters prefer this position.
Even though I say there is no right or wrong answer to this question, you will find that a little further back than center is the most common placement of a reflex sight. Seems like for most, the sweet spot is above the ejection port. Why is this? The further away from the stock, the less balanced the rifle feels and the more likely your sight won’t stay zeroed.
There are advantages to both forward and backward positioning of your reflex sight. Forward is closest to the muzzle, while backward is closest to your face.
The further away from your eye you mount your sight, the smaller the window appears. This might make it more difficult to find the illuminated red dot reticle. (Like everything in the gun industry, though, some will argue the opposite.) However, you will be able to see way more of your surroundings allowing you to retain a high level of situational awareness and see more potential threats. The closer you mount your red dot to your eye, the wider field of view your optic provides but you lose the situational awareness.
Or, if you have a magnifier, you will need to mount your reflex sight forward enough to leave room for the magnifier.
Ryan Gresham from Gun Talk explains red dot mounting in the video below.