Effect on POI when occluding red dot sights

[militarymoron]

I still can't wrap my head around that massive of a POI difference. I didn't have my Aimpoint out this weekend to even mess with this.

Well it's kind of like a person with good vision and no astigmatism wondering why someone with astigmatism is seeing a shooting star or snowman instead of a distinct red dot.
So, at 25 yds (75 ft), 1 foot equals less than one degree of angle. Look at a picture or clock on your wall about 7-8 feet away from you. Cross your eyes so you have two images (double vision). When I cross my eyes, the distance between the two images is about 4-5 feet depending on how hard I cross my eyes. That's about 30 degrees of eye misalignment.

Not everyone's eyes are aligned perfectly when one eye is occluded, so a small amount of drift/misalignment - less than a degree, can result in one foot at 25 yds. When both eyes are open, they compensate so you don't get double vision. However, as we get older, our eyes can fatigue more easily. Ever been really tired and had trouble focusing? When I was much younger, I couldn't understand why my dad had to take his glasses off to thread a needle. Now I have to do the same. I can't focus on the front sight of my handgun with my normal glasses anymore etc.

If you're don't experience it, you're fortunate, but need to understand that this is caused by differences in human vision, nothing to do with the optic or gun. If you can wrap your head around the different existing vision conditions that humans deal with on a daily basis, you can wrap your head around this

Added - Ok, I figured out a great experiment. Grab your rifle and turn on your red dot. Close the front lens cover, so you're using it occluded. Point it at any fixed object. Then cross your eyes. The dot will move a LOT from one side to another. Play around with some eye misalignments (crossing your eyes a little, a lot etc). See how much the dot moves? Then just think about how little it takes for the eyes to be misaligned to change the POI at distance. I hope that helps with understanding and visualizing it. Let me know how it goes.