Everything to Consider for Positioning a Red Dot on a Rifle
There are quite a few factors that come into play when deciding where on your rail you want to mount your red dot; more than you might think. Your decision will be influenced by the type of red dot you have, your rifle, your body, your preferences, the type of shooting you will be doing the most and how important certain types of shooting will be for you.
Most importantly, if you want to be able to use NVGs, a magnifier or back up iron sights, red dots need to be mounted far enough forward to give room for those.
Mounting a red dot farther rearward gives you a larger field of view through the red dot, but the frame will take up more of your vision. If you keep both eyes open, the frame of the red dot won’t actually block any of your vision, but you’ll see the image of the frame over top of the background environment and because it’s so close to your eye, it’s easy to focus on the environment instead of the frame. These principles that apply to the frame also apply to killflashes: the closer to your eye the killflash is, the more of your vision the killflash will take up but it’ll be easier to focus on the environment through it. Because of having a larger field of view through the red dot, you will be able to see the reticle when your eye is less centered behind the red dot.
Mounting red dots farther forward creates the opposite effects. It gives you a smaller field of view through the red dot but the frame will take up less of your vision. The frame still won’t actually block any of your vision if you keep both eyes open but the farther from your eyes the frame gets, the harder it is for your eyes to focus on the environment instead of the frame. As before, killflashes are affected by the distance the same as the frame. Because of having a smaller field of view through the red dot, you won’t be able to see the reticle until your eye is more centered behind the red dot.
Mounting a red dot farther forward makes it more likely to snag on or contact objects in the environment.
When short stocking with the stock turned sideways and put over your shoulder, having your red dot mounted farther forward can give you more room to bring the rifle back without sacrificing any of the angle you’re trying to achieve if you’re making a turn to the right while holding the rifle on your right side or making a turn to the left while holding the rifle on your left side.
The farther rearward your red dot is, the less likely vegetation or other objects in the environment will come between your eye and your red dot and block your ability to see your reticle. This is mostly eliminated when using a magnifier or NVGs.
Being mounted farther rearward makes it more likely that you will breathe on your red dot and fog it up.
The farther rearward your red dot is, the fewer reflections you will have on the back lens when you’re looking through it because your body, particularly your head, will block more of the light sources that cause those reflections. In some lighting conditions with certain optic lenses, these reflections can be a big hindrance to your ability to see through your optic.
The more rearward your red dot is mounted, the closer to your body the weight is, which puts less strain on your arms and makes it easier to quickly and precisely bring the rifle up and shift your aim.
Large, low red dots mounted at the rear can make it more difficult to use a charging handle or bolt.
Mounting a red dot at the rear, especially when it’s a tall one, makes it more likely that you could hit your face on it when changing positions quickly, especially going prone.
