Reflex Sights/Holographic Sights/Red dot Sights

It is undeniable that reflex or illuminated sights can allow for faster shooting if you keep both eyes open and focus on the target. But not everybody shoots with both eyes open and not everybody actually aims, or keeps both eyes open and focused during the shot. There is no shame in that. To keep both eyes open while multiple explosions occur within your hands is an unnatural act. It takes practice to overcome your body’s physiology. Our ancestors had little benefit in stopping and staring while loud noises happened close to them, so just remember it is supposed to be hard to do. Just know that if you have not mastered it, you may not get the full benefits of a reflex sight. 
A benefit to reflex sights over a regular illuminated reticle 

Parallax free:

Reflex sights are projected on a single plane. That means from any viewing angle, the reticle stays on target and represents a constant aiming point from the rifle. All that needs to line up (on a zeroed sight) is the reticle and the target. So long as you can see the reticle, what you see is what you get.
By comparison, iron sights need 4 planes to line up. Your eye, rear sight, front sight and target. If you move your head around, they don’t line up exactly and just because you see front sight, does not mean you are on target. The same is true for regular scopes. While you only see 1 reticle, there is more than one plane inside the sight. So if your eyes are not lined up behind it, the reticle might seem on target, but it is actually slightly off. 

Issues with reflex sights: Leave them on or leave them off?

Anything that runs on batteries is going to fail at some point. For a home defense situation, running a reflex sight constantly may be excessive, but then what happens if you need your weapon fast? The almost unanimous consensus among my buddies is that if the weapon is in your hands, the sight is on. If it is not, the sight is off and backup sights are flipped up.

Tips on using a reflex sight

Don’t focus on the dot. Unlike regular sights, iron or otherwise, the reticle or front sight should not be what you focus on. If you do, it can appear to swim around or even change shape. Instead, focus on the target and the reticle will stabilize. 
Keep the reticle as dim as possible. A 1MOA reticle can grow much bigger with unneeded brightness. As dim as you can set it while not washing out in the brightest light of the day is how you want it. 
Always, always have back up irons on any kind of duty gun that uses a reflex sight.  Unless, of course the reflex sight IS the backup to another scope.

Night vision and illuminated reticles

Many say they have night vision settings and sure enough, they work well with night vision. You might hope the setting makes the reticle from visible light to IR. But it does not, it just makes the reticle really dim. Too dim to see with the naked eye usually.  The good thing about that is any reflex sight can be used with night vision. All you have to do is dim it down as far as it goes. I have yet to find one that didn't work.  A fun fact about the older (and maybe the newer ones) Aimpoints is that they don’t actually turn off. Even in the off position you can see the reticle with night vision. And yet, somehow the battery still lasts for months with even daily use.

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